Article: 221970 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: About dipoles and current/voltage nodes Date: Tue, 28 Feb 2006 22:03:42 -0600 Message-ID: <7955-44051D1E-1114@storefull-3256.bay.webtv.net> References: Bob, VK2YQA wrote: "The question is this. If one hangs a 1/2-wave dipole in free space I assume it receives such that current maximums are at the centre and voltage maximums at the ends. Is this the case whether a feedline is connected or not?" Yes, but you must have continuity between both halves of the dipole. If you disconnect the feedline leaving an open circuit gap in the dipole at its centre, you no longer have a 1/2-wave dipole of the same frequency. You have (2) lengths of wire and each has its first resonance at about twice the frequency of first resonance of your original dipole. Best rergards, Richard Harrison, KB5WZI Article: 221971 of rec.radio.amateur.antenna From: "Frank" References: <12058okq4o35l22@corp.supernews.com> <44031031.9050905@comcast.net> <8eFMf.6418$dg.3208@clgrps13> <1206ib348gjnb4@corp.supernews.com> <4403BF4F.80702@comcast.net> <1207oqqsdjk4eab@corp.supernews.com> <4403EA1D.4090802@comcast.net> <12082j8tknvfi05@corp.supernews.com> Subject: Re: antenna impedance - calculated 10 - 20 Ohms - measured 36 Ohms?? Message-ID: Date: Wed, 01 Mar 2006 04:25:04 GMT "Roy Lewallen" wrote in message news:12082j8tknvfi05@corp.supernews.com... > dansawyeror wrote: >> Thanks - I will try to figure you how to create a non lumped model for >> the inductors. Right now that is 'undiscovered country'. > > EZNEC v. 4.0 users should use Wires Window/Create/Create Helix. You'll get > many choices, including position, orientation, various ways of specifying > the pitch and number of turns, twist direction, and so forth. (EZNEC demo > users can create any size helix to see how it works, but won't be able to > run a calculation unless the helix is extremely simple.) In NEC, use a GH > 'card'. > > There should be at least a wire diameter of air space between turns, > preferably several. (That is, the center-center distance between the wires > in one turn and the wires in adjacent turns should be at least two wire > diameters, preferably more.) If air spacing is less than 2 or 3 wire > diameters, the calculated loss will be somewhat lower than reality because > NEC (or EZNEC) doesn't account for proximity effect. > > Roy Lewallen, W7EL As I understand NEC; large errors can be introduced by junctions of dissimilar wire diameters, and in particular when the wires are at 90 deg. Therefore, when you have designed your "GH" inductors, the rest of the antenna should by constructed of the same diameter wire. This may be difficult since Dan is using two coils of significantly different Qs. I guess you could overcome this problem by varying the conductivity of the inductor to obtain the desired Q. Also, since segmentation tends to be relatively high in a helix, should segment length tapering be applied to those segments adjacent to the helix? Frank, VE6CB Article: 221972 of rec.radio.amateur.antenna From: "Jerry Martes" References: <1141169364.174650.133280@i39g2000cwa.googlegroups.com> Subject: Re: Help colinear building problems Message-ID: Date: Wed, 01 Mar 2006 04:44:25 GMT wrote in message news:1141169364.174650.133280@i39g2000cwa.googlegroups.com... > Im trying to build a 6dB simple colinear for my 2.4g wireless setup. > Im using a simple setup > from: > > //martybugs.net/wireless/collinear.cgi > > It uses a short piece of 12ga copper house wire with just two one turn > loops at 1/2 wave & 3/4 wave. I have access to a network analyzer @ > work so i tried measuring the antenna'but come up with 1.4 g & 3.4 g. > No matter what i do i cant get the antenna near the 2.4 band. > Over the years Ive build many amateur band antennas of all types but > this ones got the best > of me. Hi Marty Would you be open to trying a different configuration?? This site shows how to build colinear arrays from lengths of coax http://wireless.gumph.org/articles/homemadeomni Jerry > Article: 221973 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: antenna impedance - calculated 10 - 20 Ohms - measured 36 Ohms?? Date: Tue, 28 Feb 2006 21:37:57 -0800 Message-ID: <120acppce6jle62@corp.supernews.com> References: <12058okq4o35l22@corp.supernews.com> <44031031.9050905@comcast.net> <8eFMf.6418$dg.3208@clgrps13> <1206ib348gjnb4@corp.supernews.com> <4403BF4F.80702@comcast.net> <1207oqqsdjk4eab@corp.supernews.com> <4403EA1D.4090802@comcast.net> <12082j8tknvfi05@corp.supernews.com> Frank wrote: > > As I understand NEC; large errors can be introduced by junctions of > dissimilar wire diameters, and in particular when the wires are at 90 deg. > Therefore, when you have designed your "GH" inductors, the rest of the > antenna should by constructed of the same diameter wire. This may be > difficult since Dan is using two coils of significantly different Qs. I > guess you could overcome this problem by varying the conductivity of the > inductor to obtain the desired Q. Also, since segmentation tends to be > relatively high in a helix, should segment length tapering be applied to > those segments adjacent to the helix? > > Frank, VE6CB It's difficult to give an absolute answer to these questions, but some general comments and guidelines should help. First, the error introduced by NEC-2 when wires of dissimilar diameter are connected is generally small, unless the wires are grossly different. This error can be minimized by making the segments as *long* as possible adjacent to the junction, which of course is contrary to the general principle that more segments are better. Even a small error can cause major changes in the pattern when the dissimilar diameter wires are in a parasitic element. EZNEC and a number of other programs have a built-in method of avoiding this problem for certain antenna types, but plain NEC-2 doesn't. NEC-4 is relatively free of this problem, but it's quite expensive for hobby use. The Q of an inductor is determined by the inductance and the loss. The loss is a function of the dielectric, wire resistance, and radiation (which isn't really loss, but lowers Q as though it were). NEC type programs automatically account for the radiation, and it's easy to include wire loss. So assuming negligible dielectric loss, the programs should predict Q fairly accurately -- except for proximity affect. Proximity effect could be modeled in NEC by increasing the resistivity of the wires in the coil. EZNEC currently allows only a single wire resistivity for the whole model (although this will probably change in the next version). However, since the overall loss will be dominated by the inductors, the higher resistivity could be specified for the whole model without sacrificing significant accuracy. Alternatively, a number of resistive loads could be inserted in the inductors. Segment length tapering usually isn't necessary with NEC based programs, unless there's a source near a place where the segment length changes. An average gain check should be run to determine if there's a problem. If there is, segment length tapering is one tool which can be tried in improving the average gain. Roy Lewallen, W7EL Article: 221974 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: 80m mobile antenna question References: Message-ID: <44053ca7_4@newsfeed.slurp.net> Date: 1 Mar 2006 01:18:15 -0500 I can't prove this but I suspect there will be very little difference. The wavelength on 80/75 meters is so much longer than the car body that going from a low mount to a high one will be almost unnoticeable. Ground loss will be about the same because the capacitance between the car body and ground is the important factor and does not depend on where the whip is mounted. What will matter greatly is the Q of the coil. Make it inherently as high as you can and keep it away from metal parts of the car body. Resonate it and match it and you will have lots of fun. 80/75 is a great band for mobile and much underused. Bill, W6WRT Article: 221975 of rec.radio.amateur.antenna Date: Wed, 01 Mar 2006 00:59:20 -0700 From: BKR Subject: Re: Help colinear building problems References: <1141169364.174650.133280@i39g2000cwa.googlegroups.com> Message-ID: <44055454$1@nntp.zianet.com> Your link was slightly in error. Here is a corrected version: http://wireless.gumph.org/articles/homemadeomni.html Jerry Martes wrote: > wrote in message > news:1141169364.174650.133280@i39g2000cwa.googlegroups.com... > >>Im trying to build a 6dB simple colinear for my 2.4g wireless setup. >>Im using a simple setup >>from: >> >>//martybugs.net/wireless/collinear.cgi >> >>It uses a short piece of 12ga copper house wire with just two one turn >>loops at 1/2 wave & 3/4 wave. I have access to a network analyzer @ >>work so i tried measuring the antenna'but come up with 1.4 g & 3.4 g. >>No matter what i do i cant get the antenna near the 2.4 band. >>Over the years Ive build many amateur band antennas of all types but >>this ones got the best >>of me. > > > > Hi Marty > > Would you be open to trying a different configuration?? This site shows > how to build colinear arrays from lengths of coax > > http://wireless.gumph.org/articles/homemadeomni > > Jerry > > > > Article: 221976 of rec.radio.amateur.antenna From: condor Subject: pse info balun Message-ID: Date: Wed, 01 Mar 2006 10:55:02 GMT I will made a dipole for 10.1 Mhz v inverted, with total lenght 15 mtrs. What is the appropriate balun ? 1:1 1:2 1:5 or others ? tnx Article: 221977 of rec.radio.amateur.antenna From: Dot Subject: Re: pse info balun Message-ID: References: Date: Wed, 01 Mar 2006 06:40:38 -0500 On Wed, 01 Mar 2006 10:55:02 GMT, condor wrote: >I will made a dipole for 10.1 Mhz v inverted, with total lenght 15 mtrs. >What is the appropriate balun ? 1:1 1:2 1:5 or others ? tnx An inverted V antenna with it's legs pointing downward at about 30 degree angles should present an impedance of about 52 ohms and will not need an impedance matching device. A balun, which is not an impedance matching device, is a good idea. Mount it as close to the antenna's feedpoint as possible to tame feedline radiation that might degrade the performance of the antenna and seriously piss off your neighbors. The easiest one is this... http://www.hamuniverse.com/balun.html Article: 221978 of rec.radio.amateur.antenna From: "Jeff Dieterle" Subject: Coax help Date: Wed, 1 Mar 2006 08:57:51 -0500 Message-ID: Can anyone direct me to a web sight that explains the differences between the various coax cables, RG6, RG8, RG11, RG59. From what I've seen it basically the gauge of the conductor. Article: 221979 of rec.radio.amateur.antenna From: Dot Subject: Re: Coax help Message-ID: References: Date: Wed, 01 Mar 2006 09:16:59 -0500 On Wed, 1 Mar 2006 08:57:51 -0500, "Jeff Dieterle" wrote: >Can anyone direct me to a web sight that explains the differences between >the various coax cables, RG6, RG8, RG11, RG59. From what I've seen it >basically the gauge of the conductor. The key differences are impedence, loss, velocity factor and diameter. An example chart here. http://www.wb8erj.com/coaxloss.htm For detailed information contact your local electronics dealer, find out what he sells, then get the manufacturer's data sheets. Article: 221980 of rec.radio.amateur.antenna From: chuck Subject: Re: Q about balanced feed line References: <1206jvk3rsclp55@corp.supernews.com> Message-ID: Date: Wed, 01 Mar 2006 15:04:23 GMT I keep forgetting some of these principles. Thanks very much for the detailed and helpful explanations, Roy. 73, Chuck Roy Lewallen wrote: > chuck wrote: > >> As a follow-up, is there a practical way to determine how much current >> unbalance will cause a one dB reduction in power delivered to the >> antenna, the "lost power" being that power radiated by the >> transmission line? >> >> It seems like a rather complex modeling problem. >> >> Thanks! >> >> Chuck, NT3G > > > Nope. You can't generally say that one part of an antenna is radiating a > particular amount of the total power. Each part of the antenna creates a > field, and it interacts with the fields from all other parts of the > antenna. The total power radiated has to equal the total power input > less loss, but that's all you can say for sure. An example will help > illustrate the problem. Consider a parasitic element in a Yagi. It has > considerable current and contributes a great deal to the overall > pattern. Yet the total power input to the Yagi element is zero. With > zero power input, it can't, by itself, be radiating any power. What it > does is intercept some of the power radiated by the driven element and > re-radiates it with a different phase and amplitude. So how would you > apportion the power radiated by the driven element and the parasitic > element? > > You might take a look at the current in the driven element and note that > it increases or decreases as you put the parasitic element in place and > remove it. But the current can either increase or decrease, depending on > the length and spacing of the parasitic element. So has the parasitic > element increased or decreased the power radiated by the driven element? > There's no answer. > > You can look at the change in pattern in some idealized cases by > modeling. This can tell you what range of effects you might expect in a > real situation. > > Roy Lewallen, W7EL > Article: 221981 of rec.radio.amateur.antenna From: Bob Bob Subject: Re: About dipoles and current/voltage nodes References: <9th9025nqnmh2h5akisv3v7ll0oo3gn69i@4ax.com> <9vda02phh8315lpi2i6vn40iofv9l1om66@4ax.com> Message-ID: Date: Wed, 01 Mar 2006 09:19:37 -0600 Hi Richard >>I was surprised that the sensor line was so long and so > On the order of 1.5 cM? It is a "U shape". The section parallel to the output stripline is maybe 1cm long (going from memory). The leg length may then put the total size at more like 2cm. --- >>I am thinking also that the 50 ohm output is not being preserved as it >>goes past the sensor stripline. > What does that mean? I am suggesting that given the proximity of the sensor section it presents a significant Z bump. Like I said I dont have a feeling for the track dimensions for stripline etc at microwave. Not that it wouldnt be difficult to look it up mind you! --- >>I think the freq coverage for this model >>is about 10.5 to 11.5GHz. Keep in mind that this really is the frist >>time I have seen microwave TX's up close so my gut feelings about track >>sizes/spacing may be way off. > Check the resistor. One of the first things done. At DC of course. Dont think I ever replaced it. Was considering playing with it last time but since moving the frequency also bought it back to normal operating conditon I couldnt see it as a reason. Cheers Bob VK2YQA Article: 221982 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: 80m mobile antenna question References: <44053ca7_4@newsfeed.slurp.net> <1141235031.104775.60590@t39g2000cwt.googlegroups.com> Message-ID: Date: Wed, 01 Mar 2006 18:29:49 GMT nm5k@wt.net wrote: > What we found at the CA shootouts is that when the bottom > section runs closely parallel to the vehicle body, as it > does with a trailer hitch mount on an SUV, the field > strength is much lower than if that bottom section is > in the clear, e.g. mounted on the roof of the SUV..... > > I often wonder about this myself, but never get around to trying a > bumper mount. In the past, I've always preferred to have the lower > mast and coil as clear of the body as possible. But on the other > hand, if I mounted the base on the bumper, I could have a longer > mast below the coil. What worked like a charm for me was using the trailer hitch hole on my GMC pickup and removing the tailgate. I looked for a fiberglass aftermarket tailgate but couldn't find one. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221983 of rec.radio.amateur.antenna From: dplatt@radagast.org (Dave Platt) Subject: Re: 80m mobile antenna question Date: Wed, 01 Mar 2006 18:57:39 -0000 Message-ID: <120brl3p0a1rh94@corp.supernews.com> References: <44053ca7_4@newsfeed.slurp.net> In article , Cecil Moore wrote: >What we found at the CA shootouts is that when the bottom >section runs closely parallel to the vehicle body, as it >does with a trailer hitch mount on an SUV, the field >strength is much lower than if that bottom section is >in the clear, e.g. mounted on the roof of the SUV. That seems to match up with various peoples' experiences that I've heard. Close spacing in this way makes the signal weaker, and also seems to make the antenna more difficult to tune/match properly. This also makes sense from an engineering point of view. The closely-parallel spacing of the bottom section and the metal vehicle body would form a transmission line of sorts. This transmission-line section would not radiate much (or efficiently) - its radiation resistance would be quite low. As a result, the antenna's feedpoint impedance would be lower than otherwise (requiring a more aggressive impedance step-up of some sort to match a 50-ohm line). The coil and whip would be above the body, and would still be able to radiate, but you'd be left with something akin to a bottom-loaded whip with no high-current radiating section, rather than a center-loaded radiator with a low-loss high-current radiating section below the coil. In effect, a close/parallel mounting of this sort would seem to sacrifice much of the radiating power of this type of antenna. -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! Article: 221984 of rec.radio.amateur.antenna From: "Caveat Lector" References: Subject: Re: Coax help Message-ID: Date: Wed, 1 Mar 2006 13:39:03 -0800 Several URL's to look at http://ac6v.com/techref.htm#coax -- CL -- I doubt, therefore I might be ! "Jeff Dieterle" wrote in message news:afeb0$4405a863$424980aa$9130@COMTECK.COM... > Can anyone direct me to a web sight that explains the differences between > the various coax cables, RG6, RG8, RG11, RG59. From what I've seen it > basically the gauge of the conductor. > Article: 221985 of rec.radio.amateur.antenna From: "Frank's" References: <12058okq4o35l22@corp.supernews.com> <44031031.9050905@comcast.net> <8eFMf.6418$dg.3208@clgrps13> <1206ib348gjnb4@corp.supernews.com> <4403BF4F.80702@comcast.net> <1207oqqsdjk4eab@corp.supernews.com> <4403EA1D.4090802@comcast.net> <12082j8tknvfi05@corp.supernews.com> <120acppce6jle62@corp.supernews.com> Subject: Re: antenna impedance - calculated 10 - 20 Ohms - measured 36 Ohms?? Message-ID: <5JoNf.7747$Ui.2219@edtnps84> Date: Wed, 01 Mar 2006 21:53:05 GMT "Roy Lewallen" wrote in message news:120acppce6jle62@corp.supernews.com... > Frank wrote: >> >> As I understand NEC; large errors can be introduced by junctions of >> dissimilar wire diameters, and in particular when the wires are at 90 >> deg. Therefore, when you have designed your "GH" inductors, the rest of >> the antenna should by constructed of the same diameter wire. This may be >> difficult since Dan is using two coils of significantly different Qs. I >> guess you could overcome this problem by varying the conductivity of the >> inductor to obtain the desired Q. Also, since segmentation tends to be >> relatively high in a helix, should segment length tapering be applied to >> those segments adjacent to the helix? >> >> Frank, VE6CB > > It's difficult to give an absolute answer to these questions, but some > general comments and guidelines should help. > > First, the error introduced by NEC-2 when wires of dissimilar diameter are > connected is generally small, unless the wires are grossly different. This > error can be minimized by making the segments as *long* as possible > adjacent to the junction, which of course is contrary to the general > principle that more segments are better. Even a small error can cause > major changes in the pattern when the dissimilar diameter wires are in a > parasitic element. EZNEC and a number of other programs have a built-in > method of avoiding this problem for certain antenna types, but plain NEC-2 > doesn't. NEC-4 is relatively free of this problem, but it's quite > expensive for hobby use. > > The Q of an inductor is determined by the inductance and the loss. The > loss is a function of the dielectric, wire resistance, and radiation > (which isn't really loss, but lowers Q as though it were). NEC type > programs automatically account for the radiation, and it's easy to include > wire loss. So assuming negligible dielectric loss, the programs should > predict Q fairly accurately -- except for proximity affect. Proximity > effect could be modeled in NEC by increasing the resistivity of the wires > in the coil. EZNEC currently allows only a single wire resistivity for the > whole model (although this will probably change in the next version). > However, since the overall loss will be dominated by the inductors, the > higher resistivity could be specified for the whole model without > sacrificing significant accuracy. Alternatively, a number of resistive > loads could be inserted in the inductors. > > Segment length tapering usually isn't necessary with NEC based programs, > unless there's a source near a place where the segment length changes. An > average gain check should be run to determine if there's a problem. If > there is, segment length tapering is one tool which can be tried in > improving the average gain. > > Roy Lewallen, W7EL Thanks for the information Roy, all remarks noted and saved. Will see what I can do to generate some realistic helical models. Frank VE6CB Article: 221986 of rec.radio.amateur.antenna From: "west" Subject: 3 Monos or a Tribander? Message-ID: Date: Wed, 01 Mar 2006 22:21:10 GMT Just purchased a (tri-band 2, 1.25, .7 meters) Kenwood TH-F6A HT and was wondering what I should use for a base antenna that will be over 60ft high (bet I'll get tons of intermod). One thought is to purchase the best tri-bander available or, perhaps there is too much compromise with an all-in-one. Would you use a dual bander and a mono, which band is the dual & which the mono or 3 monos? Of course with anything other than a tri-bander, a triplexer will be needed. Oh what trying decisions a ham must make! Any comments most welcomed. 73s west AF4GC Article: 221987 of rec.radio.amateur.antenna From: "Steve Nosko" Subject: Re: Coax help Date: Wed, 1 Mar 2006 16:42:37 -0600 Message-ID: References: Do a Google on : Coax RG8 belden RG58 Loss or variations thereof... There is loss, impedance and size as the primary things that are important. 73, Steve, K9DCI "Jeff Dieterle" wrote in message news:afeb0$4405a863$424980aa$9130@COMTECK.COM... > Can anyone direct me to a web sight that explains the differences between > the various coax cables, RG6, RG8, RG11, RG59. From what I've seen it > basically the gauge of the conductor. > > Article: 221988 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: pse info balun Date: Wed, 1 Mar 2006 23:58:11 +0000 (UTC) Message-ID: References: <%cgNf.55430$dW3.11004@newssvr21.news.prodigy.com> "Cecil Moore" wrote > What kind of feedline are you using? In any case, > a good 1:1 choke-balun is preferred. ========================================= How do you select a good choke balun from amongst all the others. --- Reg. Article: 221989 of rec.radio.amateur.antenna From: "Jerry" References: <44053ca7_4@newsfeed.slurp.net> <1141235031.104775.60590@t39g2000cwt.googlegroups.com> Subject: Re: 80m mobile antenna question Message-ID: <1OrNf.42759$X7.21026@bignews7.bellsouth.net> Date: Wed, 1 Mar 2006 20:26:17 -0500 "Cecil Moore" wrote in message news:xKlNf.36179$Jd.27783@newssvr25.news.prodigy.net... > nm5k@wt.net wrote: >> What we found at the CA shootouts is that when the bottom >> section runs closely parallel to the vehicle body, as it >> does with a trailer hitch mount on an SUV, the field >> strength is much lower than if that bottom section is >> in the clear, e.g. mounted on the roof of the SUV..... >> >> I often wonder about this myself, but never get around to trying a >> bumper mount. In the past, I've always preferred to have the lower >> mast and coil as clear of the body as possible. But on the other >> hand, if I mounted the base on the bumper, I could have a longer >> mast below the coil. > > What worked like a charm for me was using the trailer hitch > hole on my GMC pickup and removing the tailgate. I looked > for a fiberglass aftermarket tailgate but couldn't find one. > -- > 73, Cecil http://www.qsl.net/w5dxp With that in mind, I have a friend who has a Ford Exploder--I mean, EXPLORER :) --- with his DK3 mounted on a homebrew mount level with the rear bumper. The bad part of it (IMHO) is the loading coil is level with the body about where the rear window is and about 8 inches from the body. I mentioned to him that it would be better to get the coil up in the clear above the truck, but he is says he can't get in his carport. Well, what about this: move the coil UP to clear the body and use a shorter whip? IOW, faced with the lesser of two evils, which would be better. Left as is with longer whip and putting up with the loss caused by proximity to body metal, or coil clearing the top of the truck and a shorter whip--even it it has to be 5 feet instead of 6 1/2? I voted for the higher coil and shorter whip. What say ye? :) 73 Jerry K4KWH Article: 221990 of rec.radio.amateur.antenna Date: Wed, 01 Mar 2006 19:28:10 -0600 From: Tom Ring Subject: Re: need help with H antenna References: Message-ID: <44064a2a$0$7335$39cecf19@news.twtelecom.net> Jim wrote: > I need help in building an H type of tracking antenna for use around 166-167 > mhz. This is for wildlife tracking. I have a couple of handheld 3 element > Yagi's that I built using YagiCad to do the math, and they work well, but > they are big and clunky. > > There are times when I am willing to sacrifice the good f/b ratio of the > yagi for convienience, for instance when working in brushy woods. I have > used an H for tracking at 151 mhz, but of course, I can't use that one for > 166. > > My tracking receiver, a King portable, has a BNC connector, so I can > interchange antennas quickly. > > Is there a web page or magazine article that can help me design my H, or can > someone share their experience? > > Thanks > Jim > > I am assuming you mean a 2 element beam with both elements driven. If so, I would recommend trying to make a 2 meter version of Roy W7EL's version of the ZL special. I just messed around with his downloadable program for 15 minutes and got a reasonable version hacked up for your frequency. The impedance wasn't perfect, about 1.5 at best and about 3 to 1 SWR +-1.5 MHz, but you are receive only, so that's not a big deal. Heck, he may notice this response and tell you he's done one and what he came up with for lengths. Tom K0TAR Article: 221991 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: pse info balun Date: Wed, 01 Mar 2006 17:54:20 -0800 Message-ID: <120ck2den5gmhc2@corp.supernews.com> References: <%cgNf.55430$dW3.11004@newssvr21.news.prodigy.com> Reg Edwards wrote: > > How do you select a good choke balun from amongst all the others. > --- The important characteristic is common mode impedance. Tie the two input conductors together and the two output conductors together, and measure the input-to-output impedance. This can be done in various ways, most easily with an antenna analyzer, or by other means. The higher the impedance, the better. 1000 ohms seems to be a good number to shoot for, with 500 ohms probably being ok for most applications. The angle of the impedance doesn't matter unless you're running high power, in which case it might be necessary to keep the impedance more reactive than resistive to prevent excessive core heating. A good choke balun for multiple band use will have a high common mode impedance on all bands on which it'll be used. Narrower band ones can be connected in series as an alternative. Roy Lewallen, W7EL Article: 221992 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: pse info balun References: <%cgNf.55430$dW3.11004@newssvr21.news.prodigy.com> Message-ID: Date: Thu, 02 Mar 2006 04:12:03 GMT Reg Edwards wrote: > How do you select a good choke balun from amongst all the others. I roll my own. I have 8 FB-77-5621 cores over a piece of RG-400 in series with an FT-240-61 with ten turns of RG-400. The latter comes in a ~$10 balun kit from Amidon. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221993 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: 80m mobile antenna question References: <44053ca7_4@newsfeed.slurp.net> <1141235031.104775.60590@t39g2000cwt.googlegroups.com> <1OrNf.42759$X7.21026@bignews7.bellsouth.net> Message-ID: Date: Thu, 02 Mar 2006 04:15:36 GMT Jerry wrote: > I voted for the higher coil and shorter whip. What say ye? :) Within reason, the higher the coil, the better. I only had one foot of antenna above my coil, a one foot section upon which was mounted a large horizontal top hat. -- 73, Cecil http://www.qsl.net/w5dxp Article: 221994 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: 80m mobile antenna question References: <44053ca7_4@newsfeed.slurp.net> <1141235031.104775.60590@t39g2000cwt.googlegroups.com> Message-ID: <440674bf_3@newsfeed.slurp.net> Date: 1 Mar 2006 23:29:51 -0500 ORIGINAL MESSAGE: nm5k@wt.net wrote: > What we found at the CA shootouts is that when the bottom > section runs closely parallel to the vehicle body, as it > does with a trailer hitch mount on an SUV, the field > strength is much lower than if that bottom section is > in the clear, e.g. mounted on the roof of the SUV..... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ No doubt that is correct. So how about this: I have a '95 Thunderbird which I dearly love and don't want to cut holes in. I've been think of going to a welding shop and having a metal piece made which I could bolt to the frame in the back and which would stick out about six inches or so behind the rear bumper, and installing a ball mount on it. This will keep the lower part of the antenna about a foot away from the body and allow a nice, long whip overall. The loading coil would be in the center, homebrew of course. :-) And not a hole in sight. Comments? Bill, W6WRT Article: 221995 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: 80m mobile antenna question References: <44053ca7_4@newsfeed.slurp.net> <1141235031.104775.60590@t39g2000cwt.googlegroups.com> Message-ID: <440674ea$1_3@newsfeed.slurp.net> Date: 1 Mar 2006 23:30:34 -0500 ORIGINAL MESSAGE: nm5k@wt.net wrote: > What we found at the CA shootouts ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Speaking of shootouts, are any scheduled for this year anywhere? Bill, W6WRT Article: 221996 of rec.radio.amateur.antenna From: "Frank" References: <12058okq4o35l22@corp.supernews.com> <44031031.9050905@comcast.net> <8eFMf.6418$dg.3208@clgrps13> <4403C93F.2040700@comcast.net> <4403EB86.3020005@comcast.net> Subject: Re: antenna impedance - calculated 10 - 20 Ohms - measured 36 Ohms?? Message-ID: Date: Thu, 02 Mar 2006 05:02:28 GMT Dan, I have been trying to replicate your inductors with NEC. It is a bit tedious, just guessing wire gauge, coil diameter etc., to obtain the desired inductance and Q. What are the physical dimensions of your inductors? Have you had any luck with GH? You may have a problem with 4nec2 since you must have a GM card along with the GH. Frank "dansawyeror" wrote in message news:4403EB86.3020005@comcast.net... > Good question. I will play with that. That said, based on Roy's comment at > minimum the load should appear nearly pure resistive. > > I just tested the Autek with 6.25, 12.5, and 25 Ohm loads. > 25 read 26 > 12.5 read 12 - 13 - 12 etc. > 6.25 read mostly 7 with an occasional 6. > > I would say for non-reactive loads it is pretty close. > > Tomorrow - will be to experiment with non lumped inductors. That will be a > challenge. > > Thanks - Dan > > > Frank wrote: >> "dansawyeror" wrote in message >> news:4403C93F.2040700@comcast.net... >> >>>Frank, >>> >>>The Autek is remarkably close. I have used it to checkout 50 and 25 Ohm >>>loads. For these two values it is very close. (It is battery level >>>sensitive.) >>> >>>The couplers are a pair of M-C ZFDC 20-4's. >>> >>>Dan >> >> >> Thanks Dan, I had forgotten about Mini-Circuits. Their price is hard to >> beat. I may pick up one of the "PDC" series dual directional couplers. >> Incidentally your code indicates resonance occurs at 3.54 MHz. I wonder >> how the Autek behaves when subjected to a reactive load does it actually >> get close to the magnitude? >> >> Frank Article: 221997 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: 80m mobile antenna question Date: Wed, 01 Mar 2006 21:35:43 -0800 Message-ID: <120d11fn5ontsb0@corp.supernews.com> References: <44053ca7_4@newsfeed.slurp.net> <1141235031.104775.60590@t39g2000cwt.googlegroups.com> <440674bf_3@newsfeed.slurp.net> Bill Turner wrote: > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > No doubt that is correct. So how about this: I have a '95 Thunderbird > which I dearly love and don't want to cut holes in. I've been think of > going to a welding shop and having a metal piece made which I could > bolt to the frame in the back and which would stick out about six > inches or so behind the rear bumper, and installing a ball mount on it. > This will keep the lower part of the antenna about a foot away from the > body and allow a nice, long whip overall. The loading coil would be in > the center, homebrew of course. :-) > > And not a hole in sight. > > Comments? > > Bill, W6WRT I'm not sure why, but most amateurs don't seem to realize that the whip isn't an "antenna" and the car "ground", but each is half of a dipole-like antenna. The car part is often much more important with regard to radiation characteristics and efficiency than the whip part. With the arrangement you suggest, the antenna consists of a vertical wire -- the whip -- and a fat, horizontal "wire" -- the car. Whatever current flows into the whip, an equal current flows over the outside of the car, originating at the base of the whip. Any antenna with a low horizontal wire will be quite lossy, because the wire's current will induce a heavy current in the lossy ground beneath the wire, or car. The best arrangement, as others have pointed out, is to mount the antenna right at the center of the top of the car. This makes the car "wire" vertical, a much more efficient arrangement, which the "shootouts" consistently show. You'll also find that larger trucks, which effectively form a longer vertical "wire" for the car part, outdo smaller ones for the same whip. Of course, sometimes you don't have any choice, and you just have to do the best you can. I once had a bumper mounted antenna consisting of a CB whip base loaded with an inductor wound on a powdered iron core to resonate on 40 meters. The car was a VW Squareback, so the antenna had the increased disadvantage of proximity between the square back and the antenna. As others have pointed out, this can reduce efficiency farther. Yet I had a successful QSO with JA while driving down Highway 101, running 8 watts, CW. So you can still communicate and have lots of fun even with a very sub-optimal system. But anyone wanting to improve his system has a much better chance of doing it if he has a basic understanding of how the antenna really works. Roy Lewallen, W7EL Article: 221998 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: need help with H antenna Date: Wed, 01 Mar 2006 21:45:33 -0800 Message-ID: <120d1jtr6triu56@corp.supernews.com> References: <44064a2a$0$7335$39cecf19@news.twtelecom.net> Tom Ring wrote: > I am assuming you mean a 2 element beam with both elements driven. > > If so, I would recommend trying to make a 2 meter version of Roy W7EL's > version of the ZL special. I just messed around with his downloadable > program for 15 minutes and got a reasonable version hacked up for your > frequency. The impedance wasn't perfect, about 1.5 at best and about 3 > to 1 SWR +-1.5 MHz, but you are receive only, so that's not a big deal. For his application, shoot for the best F/B ratio -- that is, for element currents as close to equal and the correct phase -- as possible. The forward lobe of this antenna is broader than a 3 element Yagi. It would work best as a direction finding antenna by determining the direction of the null. Quite a bit of mismatch should be tolerable unless signals are extremely weak, but if an adequate match can't be achieved, it's simple to remedy with a simple matching network. > Heck, he may notice this response and tell you he's done one and what he > came up with for lengths. Nope. I've never had occasion to design an antenna for 166 MHz. One designed for 2 meters (which I haven't done either) won't work satisfactorily at 166. Roy Lewallen, W7EL Article: 221999 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: 80m mobile antenna question References: <44053ca7_4@newsfeed.slurp.net> <1141235031.104775.60590@t39g2000cwt.googlegroups.com> <440674bf_3@newsfeed.slurp.net> <120d11fn5ontsb0@corp.supernews.com> Message-ID: <4406b31d_1@newsfeed.slurp.net> Date: 2 Mar 2006 03:55:57 -0500 Roy Lewallen wrote: > The best arrangement, as others have pointed out, is to mount the > antenna right at the center of the top of the car. This makes the car > "wire" vertical, a much more efficient arrangement, which the > "shootouts" consistently show. You'll also find that larger trucks, > which effectively form a longer vertical "wire" for the car part, > outdo smaller ones for the same whip. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Well, maybe. The problem is, the higher the mounting point, the shorter the whip has to be to be legal to drive down the road. If your car was 13 feet five inches tall, your whip could only be one inch long. How efficient would that be on 80 meters? The point being, everything is a tradeoff of one thing for another. If the shootouts say a rooftop is best, ok, but I have to say I'm surprised. At a relatively low frequency like 80 meters, the car body is more of a coupler to the earth rather than a real "ground" of it's own. Given that, then the longer the whip part, the better. HF mobile antennas are a fascinating subject and one of these days I will set up a "shootout" range on my 2.5 acres here in the desert and do some shooting of my own. Bill, W6WRT Article: 222000 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: pse info balun Date: Thu, 2 Mar 2006 11:53:52 +0000 (UTC) Message-ID: References: <%cgNf.55430$dW3.11004@newssvr21.news.prodigy.com> "Cecil Moore" wrote in message news:nguNf.17219$rL5.15156@newssvr27.news.prodigy.net... > Reg Edwards wrote: > > How do you select a good choke balun from amongst all the others. > > I roll my own. I have 8 FB-77-5621 cores over a piece > of RG-400 in series with an FT-240-61 with ten turns of > RG-400. The latter comes in a ~$10 balun kit from Amidon. > -- > 73, Cecil http://www.qsl.net/w5dxp =========================================== Ten or more turns of twin, 18 awg, stranded, speaker cable is even better. Easier to make and has higher choke impedance and lower loss. I don't know why you mess about with coax. ---- Reg. Article: 222001 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: 80m mobile antenna question References: <44053ca7_4@newsfeed.slurp.net> <1141235031.104775.60590@t39g2000cwt.googlegroups.com> <440674bf_3@newsfeed.slurp.net> Message-ID: Date: Thu, 02 Mar 2006 13:09:54 GMT Bill Turner wrote: > So how about this: I have a '95 Thunderbird > which I dearly love and don't want to cut holes in. I've been think of > going to a welding shop and having a metal piece made which I could > bolt to the frame in the back and which would stick out about six > inches or so behind the rear bumper, and installing a ball mount on it. > This will keep the lower part of the antenna about a foot away from the > body and allow a nice, long whip overall. The loading coil would be in > the center, homebrew of course. :-) The only way to improve on that on 75m would be to mount a piece of sheet metal on fiberglass poles connected at the ends of both bumpers. The piece of horizontal sheet metal, located 13.5 feet from the ground, would have the same footprint as the T-bird and would be used as the top hat. You do want optimum performance don't you? :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 222002 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: 80m mobile antenna question References: <44053ca7_4@newsfeed.slurp.net> <1141235031.104775.60590@t39g2000cwt.googlegroups.com> <440674bf_3@newsfeed.slurp.net> <120d11fn5ontsb0@corp.supernews.com> Message-ID: Date: Thu, 02 Mar 2006 13:19:27 GMT Roy Lewallen wrote: > I'm not sure why, but most amateurs don't seem to realize that the whip > isn't an "antenna" and the car "ground", but each is half of a > dipole-like antenna. My S10 trailer hitch mounted configuration exhibited considerable directivity toward the front of the pickup on 17m. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222003 of rec.radio.amateur.antenna Message-ID: <4406F37B.1B33CB65@nospam.com> From: jon Subject: Re: Coax help References: Date: Thu, 02 Mar 2006 13:30:35 GMT RG-8 is no longer a military standard RG-213 is a better choice. http://www.thewireman.com he wrote a book ! http://www.belden.com Article: 222004 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: pse info balun References: <%cgNf.55430$dW3.11004@newssvr21.news.prodigy.com> Message-ID: Date: Thu, 02 Mar 2006 13:34:04 GMT Reg Edwards wrote: > Ten or more turns of twin, 18 awg, stranded, speaker cable is even > better. > > Easier to make and has higher choke impedance and lower loss. > > I don't know why you mess about with coax. The optimum Z0 for the wire that is used is the square root of the product of the input impedance and the output impedance. I vary the length of my ladder-line to accomplish resonance in my antenna system. The impedances seen at the output of my balun averages 50 ohms. Thus, the optimum Z0 for my balun wire is 50 ohms. Magnet wire will do that but speaker cable won't. Ten turns of RG-400 is really convenient. I use RG-400 for everything inside of the shack. All the 1/2" dia. stuff is outside. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222005 of rec.radio.amateur.antenna From: Bob Bob Subject: 2m omnis and radiation takeoff angles - importance Message-ID: <0l8jd3-mag.ln1@p400bob.personal.cox.net> Date: Thu, 02 Mar 2006 07:30:39 -0600 Hi NG About ready to model and build a medium 2m antenna system. Probably run a EDZ with 5/8 elements off one side of the mast for vertical and a three element wide spaced thick element quad for horiz on the other side. The mast mount will form part of the model when I get to it. (Hoping for a cardioid pattern from the EDZ) Main element material for both antennas will probably be 1/2" copper. (That will make the quad interesting to support!) Sticking to the vertical system I am wanting to get a handle on how important the "problem" of desired low angle radiation is and what traps one should avoid. I am aware of the mast/coax decoupling issues. I also believe that the narrower the vertical beamwidth (or rather the less downward radiation) the less the ground reflection problem will be. Also wondering if adjusting phase delay or amplitude variations between the 5/8 elements would be useful in lowering the pattern. (Something I will also be modelling) Feed would probably be a 4:1 coaxial balun. Height will eventually be about 30ft above the house roof. Any thoughts, ideas and debunking most welcome Cheers Bob W5/VK2YQA Article: 222006 of rec.radio.amateur.antenna From: John Ferrell Subject: Re: 3 Monos or a Tribander? Message-ID: <620e025tnbgq20oqd0k9qq3574d967of7r@4ax.com> References: Date: Thu, 02 Mar 2006 14:28:01 GMT In my experience a super antenna for repeater operation is a problem. You bring up enough machines to create your own QRM. Keep it simple. On Wed, 01 Mar 2006 22:21:10 GMT, "west" wrote: >Just purchased a (tri-band 2, 1.25, .7 meters) Kenwood TH-F6A HT and was >wondering what I should use for a base antenna that will be over 60ft high >(bet I'll get tons of intermod). One thought is to purchase the best >tri-bander available or, perhaps there is too much compromise with an >all-in-one. Would you use a dual bander and a mono, which band is the dual & >which the mono or 3 monos? Of course with anything other than a tri-bander, >a triplexer will be needed. Oh what trying decisions a ham must make! Any >comments most welcomed. > >73s >west >AF4GC > John Ferrell W8CCW Article: 222007 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: 80m mobile antenna question References: <44053ca7_4@newsfeed.slurp.net> <1141235031.104775.60590@t39g2000cwt.googlegroups.com> <440674bf_3@newsfeed.slurp.net> Message-ID: <440711e5$1_1@newsfeed.slurp.net> Date: 2 Mar 2006 10:40:21 -0500 Cecil Moore wrote: > The only way to improve on that on 75m would be to mount > a piece of sheet metal on fiberglass poles connected at > the ends of both bumpers. The piece of horizontal sheet > metal, located 13.5 feet from the ground, would have the > same footprint as the T-bird and would be used as the top > hat. You do want optimum performance don't you? :-) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ I think my T-Bird might actually fly. :-) 73, Bill W6WRT Article: 222008 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: 80m mobile antenna question Date: Thu, 2 Mar 2006 10:56:15 -0600 Message-ID: <12478-440723AF-300@storefull-3258.bay.webtv.net> References: <120d11fn5ontsb0@corp.supernews.com> Roy Lewallen, W7EL wrote: "I`m not sure why, but most amateurs don`t seem to realize that a whip isn`t an "antenna" and the car "ground", but each is half of a dipole-like antenna." Not exactly.. In a common balanced dipole, each half has the same current quantity and direction, though in one half the current flows toward the feedpoint while it flows away in the other half. >From such a dipole, both its halves contribute equally to its radiation. Action of a common ground plane is different. When its balanced radials are perpendicular to its whip, radiation from its radials zeros out leaving the whip to do all the radiation. Ideally, a whip mounted on a vehicle or directly on the earth behaves the same. It is the whip which radiates. An antenna is also called an aerial. It is defined as that part of a radio station which radiates or receives radio waves into or from space. An antenna ground system is defined as that portion of an antenna system closely associated with the earth and including an extensive conducting surface which may be the earth itself. Most radio amateurs have it right. Best regards, Richard Harrison, KB5WZI Article: 222009 of rec.radio.amateur.antenna From: "NA" Subject: FS: Heath Marauder Transmitter Message-ID: Date: Thu, 02 Mar 2006 17:50:02 GMT I have checked with the local shipping service. Shipping via FEDX will be between $150 and $200 to most address on the US mainland. I have seen Marauders not meet the reserve on Ebay at over $150 plus shipping. I will sell this one for $100 plus the actual shipping cost charged by the local shipping store. Thanks for reading Jim N6PJQ AT Hotmail Article: 222010 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: 80m mobile antenna question Date: Thu, 02 Mar 2006 12:16:20 -0800 Message-ID: <120ekkmb2nbrk75@corp.supernews.com> References: <120d11fn5ontsb0@corp.supernews.com> <12478-440723AF-300@storefull-3258.bay.webtv.net> Richard Harrison wrote: > Roy Lewallen, W7EL wrote: > "I`m not sure why, but most amateurs don`t seem to realize that a whip > isn`t an "antenna" and the car "ground", but each is half of a > dipole-like antenna." > > Not exactly.. > > In a common balanced dipole, each half has the same current quantity and > direction, though in one half the current flows toward the feedpoint > while it flows away in the other half. > > From such a dipole, both its halves contribute equally to its radiation. > > Action of a common ground plane is different. When its balanced radials > are perpendicular to its whip, radiation from its radials zeros out > leaving the whip to do all the radiation. Ideally, a whip mounted on a > vehicle or directly on the earth behaves the same. It is the whip which > radiates. A ground plane is a poor model of how currents flow along a car body. Consider an antenna mounted on top of a car. From the base of the antenna, the current flows equally in all directions away from the base of the antenna, like a ground plane. This current doesn't contribute much radiation, for the reasons you state. But then it reaches the edge of the top of the car and flows downward. All the portions of the current are now flowing the same direction, and their fields don't cancel but add in phase. The net result is the same as if it were just flowing down a fat wire the height of the car. If the car is eight feet high, the field from the car will equal the field from an eight foot whip. In fact, unless the whip is top loaded to make the current uniform, the car will radiate more than the whip, because the capacitance of the car to ground will tend to give the car a uniform current distribution, like a top hat does to a whip. This will increase the radiated field strength from the car. Now consider a bumper mounted antenna. The current will spread from the base and proceed around the car. More will probably flow on the bottom than the top and sides due to coupling with the ground, but all portions will be flowing in the same direction and all will radiate. There is no place on the car where the current distribution or flow pattern resembles current on a ground plane. > An antenna is also called an aerial. It is defined as that part of a > radio station which radiates or receives radio waves into or from space. > > An antenna ground system is defined as that portion of an antenna system > closely associated with the earth and including an extensive conducting > surface which may be the earth itself. The problem here is that the currents don't care how you define things. They flow where the physical laws dictate. Defining "ground" doesn't make them behave differently. > Most radio amateurs have it right. If your view represents that of most amateurs, they don't. Roy Lewallen, W7EL Article: 222011 of rec.radio.amateur.antenna From: Jules Subject: Re: radar and health ? References: <8545c34b738aa8f3099fdd2334602bc0.99986@mygate.mailgate.org> Message-ID: <6qJNf.25805$8d1.12957@read1.cgocable.net> Date: Thu, 02 Mar 2006 16:26:25 -0500 I think if it is too strong it will affect your eyes first, ears then nerves/brain last. There are lots of safety precautions for wx radar on aircraft and they are generally are under 10kw for small planes, x band radar. Large jets, c band. Then there are fighter aircraft whose targeting radar has been know to kill small animals around the runways. But those are out of favour now, low power is in. Thierry wrote: > Hi, > > I received this message from a colleague but I cannot answer him. I d > not know these systems. > Could you help me ? > > My company has installed a Radar Tower for Port survaillence. The tower > is about 50 meter height on top of the of a 3 stories building roof and > my office building just below the tower on the same level, 20 meter away > from the tower. At the same time, the surrounding is my working area ( > Jetty Terminal for ships loading and unloading activities ). I can say > that I'll be around that area 12 hours a day for another 20 years. > > My question: > > Is it safe to work in that area???? > > Thanks in advance > Thierry > http://www.astrosurf.org/lombry > > Article: 222012 of rec.radio.amateur.antenna From: The Visitor Subject: Re: radar and health ? References: <8545c34b738aa8f3099fdd2334602bc0.99986@mygate.mailgate.org> <1136722082.927929.234700@o13g2000cwo.googlegroups.com> Message-ID: Date: Thu, 02 Mar 2006 16:28:44 -0500 Steve Nosko wrote: > I don't understand being "on the same level" AND being "20 feet below". Yes confusing, but I am sure there are intense lobes to look out for. Article: 222013 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: 80m mobile antenna question References: <120d11fn5ontsb0@corp.supernews.com> <12478-440723AF-300@storefull-3258.bay.webtv.net> <120ekkmb2nbrk75@corp.supernews.com> Message-ID: Date: Fri, 03 Mar 2006 00:08:42 GMT Roy Lewallen wrote: > A ground plane is a poor model of how currents flow along a car body. If the car body was 1/2WL in the air, would the antenna be more efficient? -- 73, Cecil http://www.qsl.net/w5dxp Article: 222014 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: 80m mobile antenna question References: <120d11fn5ontsb0@corp.supernews.com> <12478-440723AF-300@storefull-3258.bay.webtv.net> Message-ID: Date: Fri, 03 Mar 2006 00:12:58 GMT Dan Richardson wrote: > Roy is quite correct in stating that a vehicle's body behaves as one > side of a dipole. A lopsided dipole to be sure, but one half the > antenna just the same. Seems the truth might lie somewhere in between. If the ground plane of a vertical antenna is near the ground, there are losses. If the ground plane of a vertical antenna is located 1/2WL above ground, the losses are a lot less. I'll bet that if the vehicle were located 1/2WL in the air, the efficiency would increase. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222015 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: 80m mobile antenna question References: <120d11fn5ontsb0@corp.supernews.com> <12478-440723AF-300@storefull-3258.bay.webtv.net> <0YGdnc2vqPncEprZnZ2dnUVZ_t-dnZ2d@comcast.com> Message-ID: Date: Fri, 03 Mar 2006 01:28:06 GMT Amos Keag wrote: > Cecil Moore wrote: >> I'll bet that >> if the vehicle were located 1/2WL in the air, the efficiency >> would increase. > > Kind of tough though going under power lines, bridges and overpasses :-) What if the vehicle is a helicopter? :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 222016 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: New program CONNECT Date: Fri, 3 Mar 2006 02:03:09 +0000 (UTC) Message-ID: There have been recent discussions about the interchangeability of coaxial plugs and sockets, their dimensions and their impedances. But, as usual, the magnitude of the electrical effects is never mentioned. Without numbers nobody knows what they are talking about. A coaxial connector is a very short length of transmission line but at UHF and microwave frequencies it is an appreciable fraction of a wavelength. When 1/4-wavelength long it has the property of transforming a mismatched termination to another value. When 1/2-wavelength long the input impedance repeats the value of the termination. The SWR on an adjacent line is a function of the input impedance. What is the effect of using a 75-ohm coaxial connector in a 50-ohm system? What is the effect of using a length of transmission line of 50-ohms nominal impedance when it is actually 53 ohms? With mixed values of line Zo at what high frequency does the SWR and reflection loss become excessive? Program CONNECT.exe calculates the effect of inserting a length of line in a system of different Zo. Differences can be large or small. Line length can be physically very short. For a given frequency, mismatched Zo's and a velocity factor, input impedance, SWR, reflection coefficient and reflection loss are calculated. (Reflection loss is sometime known as mismatch loss). The program is worded in terms of a connector mismatch but has other applications. Input data can be varied in small increments from the keyboard while observing the effects on calculated values. Download CONNECT from website below. It has entertainment, educationaal and practical value. Amuse yourselves! ---- ........................................................... Regards from Reg, G4FGQ For Free Radio Design Software go to http://www.btinternet.com/~g4fgq.regp ........................................................... Article: 222017 of rec.radio.amateur.antenna From: Dot Subject: Re: 80m mobile antenna question Message-ID: <3v7f025mtmbi2cl0iv04g5ffhvoo85iuo7@4ax.com> References: <120d11fn5ontsb0@corp.supernews.com> <12478-440723AF-300@storefull-3258.bay.webtv.net> <0YGdnc2vqPncEprZnZ2dnUVZ_t-dnZ2d@comcast.com> Date: Thu, 02 Mar 2006 20:46:56 -0500 On Fri, 03 Mar 2006 01:28:06 GMT, Cecil Moore wrote: >Amos Keag wrote: > >> Cecil Moore wrote: >>> I'll bet that >>> if the vehicle were located 1/2WL in the air, the efficiency >>> would increase. >> >> Kind of tough though going under power lines, bridges and overpasses :-) > >What if the vehicle is a helicopter? :-) Then you should know better than to go flying under power lines, bridges and overpasses. Geesh... Article: 222018 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: 80m mobile antenna question Date: Thu, 2 Mar 2006 21:35:30 -0600 Message-ID: <4239-4407B982-64@storefull-3253.bay.webtv.net> References: Danny K6MHE wrote: "Boy Richard you sure missed on that one!" A broadcast tower over a perfect ground system is the source of radiated energy even though its image in the ground system produces a pattern which behaves as if there were a dipole, the lower half of which is buried. The earth is not radiating. It is conducting. The tower above the earth is the source of radiation. Every ground radial in the broadcast system (usually all 120 of them), has a twin running in the opposite direction. All radials are tied together at the base of the tower. So the current in the radials all starts out in the same phase and stays roughly in the same phase as it progresses outward. It declines in magnitude away from the feedpoint. That`s the reason ground radials don`t need to be unlimited in length. You don`t need radials after the current plays out. As current travels in opposite directions in the groind radials. the fields they prodoce add to zero. The two halves of a dipole are fed with opposite polarities at their feedpoint. this puts the two halves running in opposite directions in-phase. Their fields thus reinforce. A 1/4-wave ground plane in free space has the same power gain as a center-fed 1/2-wave dipole. The matched power radiated by either ground plane or dipole is the same, but the resistance at the feedpoint of the ground plane is only 50% that of the dipole. Radiation resistance is defined as the resistance at the high current point of the antenna unless otherwise specified. Radiated power is (I) squared times the radiation resistance. Danny did not specify where he thought I erred in my previous posting. I said that a whip mounted on a vehicle is not exactly like a dipole. I meant that the whip did most of the radiating because it carried a concentration of current in the same direction while in the car body the current is dispersed in various directions, some of which canncel in their effects. I still insist that is the case. Best regards, Richard Harrison, KB5WZI Article: 222019 of rec.radio.amateur.antenna From: "Frank" References: <12058okq4o35l22@corp.supernews.com> <44031031.9050905@comcast.net> <8eFMf.6418$dg.3208@clgrps13> <4403C93F.2040700@comcast.net> <4403EB86.3020005@comcast.net> <440707DD.1030601@comcast.net> Subject: Re: antenna impedance - calculated 10 - 20 Ohms - measured 36 Ohms?? Message-ID: Date: Fri, 03 Mar 2006 05:39:42 GMT "dansawyeror" wrote in message news:440707DD.1030601@comcast.net... > Frank, > > A 'target' coil is 300mm x 300mm of 5/16 copper tubing. It is about 50 > feet of tubing, a .5 pitch, and should be close to 75 uH. This should be > close. From there simulation should show the best performance between > varying the coils. > > Thanks - Dan Having trouble producing a good model Dan. NEC 2 indicates Qs which are >5000, but no warnings or errors. I can run it in NEC 4.1, single, and double precision, but I get over 400 warnings in the NEC output file; such as: SEGCHK: WARNING - SEGMENTS 1 AND 271 CROSS AT A MIDPOINT WITH SEPARATION LESS THAN THE SUM OF THEIR RADII SEGCHK: WARNING - THE CENTER OF SEGMENT 1 IS WITHIN THE VOLUME OF SEGMENT 271 These warnings are particularly strange since, for example, absolute segments 1 and 271 are almost 12" apart in the model. Will see what I can do to correct the error. 73, Frank The code I am using is as follows: CM Inductor Q Calculation CE GH 1 300 1 12 6 6 6 6 0.3125 GW 2 5 6 0 12 0 0 12 0.3125 GW 3 10 0 0 12 0 0 0 0.3125 GW 4 5 0 0 0 6 0 0 0.3125 GS 0 0 0.025400 GE 0 EX 0 3 5 00 1 0 FR 0 5 0 0 3.7 0.02 LD 5 1 1 320 5.7001E7 RP 0 181 1 1000 -90 90 1.00000 1.00000 EN Article: 222020 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: 80m mobile antenna question References: <4239-4407B982-64@storefull-3253.bay.webtv.net> Message-ID: <4407d7ba$1_1@newsfeed.slurp.net> Date: 3 Mar 2006 00:44:26 -0500 ORIGINAL MESSAGE: Dan Richardson wrote: > That may have some validity in the VHF and higher ranges, but on HF - > particularly on 80 meters - a car body's size is a small fraction of a > wavelength (as is the whip portion). Consequently the vehicle body > acts like the one half of a dipole antenna. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Q. How can a car body which is a "small fraction" of a wavelength act like one half of a dipole? A. It can't. Q. Well, what does it do then? A. It acts like a short piece of wire leading from the bottom of the whip to the actual ground plane, namely the earth itself. Q. Does that help any? A. Probably a little, but remember the piece of wire (the car body) is only a few feet long. Not very much on 80 meters. Q. Thanks, I get it now. A. You're welcome. 73, Bill W6WRT Article: 222021 of rec.radio.amateur.antenna From: "David G. Nagel" Subject: Re: 80m mobile antenna question Date: Fri, 03 Mar 2006 00:24:00 -0600 Message-ID: <120fo85epbaj24d@corp.supernews.com> References: <4239-4407B982-64@storefull-3253.bay.webtv.net> <4407d7ba$1_1@newsfeed.slurp.net> Bill Turner wrote: > ORIGINAL MESSAGE: > > Dan Richardson wrote: > > >>That may have some validity in the VHF and higher ranges, but on HF - >>particularly on 80 meters - a car body's size is a small fraction of a >>wavelength (as is the whip portion). Consequently the vehicle body >>acts like the one half of a dipole antenna. > > > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > Q. How can a car body which is a "small fraction" of a wavelength act > like one half of a dipole? > > A. It can't. > > Q. Well, what does it do then? > > A. It acts like a short piece of wire leading from the bottom of the > whip to the actual ground plane, namely the earth itself. > > Q. Does that help any? > > A. Probably a little, but remember the piece of wire (the car body) is > only a few feet long. Not very much on 80 meters. > > Q. Thanks, I get it now. > > A. You're welcome. > > 73, Bill W6WRT Actually it is acting as one half of a dipole. It is just a non-resonant half of a dipole. Remember "di" means two. Dave WD9BDZ Article: 222022 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: antenna impedance - calculated 10 - 20 Ohms - measured 36 Ohms?? Date: Fri, 03 Mar 2006 00:11:27 -0800 Message-ID: <120fuhhaaj786dc@corp.supernews.com> References: <12058okq4o35l22@corp.supernews.com> <44031031.9050905@comcast.net> <8eFMf.6418$dg.3208@clgrps13> <4403C93F.2040700@comcast.net> <4403EB86.3020005@comcast.net> <440707DD.1030601@comcast.net> Frank wrote: > "dansawyeror" wrote in message > news:440707DD.1030601@comcast.net... >> Frank, >> >> A 'target' coil is 300mm x 300mm of 5/16 copper tubing. It is about 50 >> feet of tubing, a .5 pitch, and should be close to 75 uH. This should be >> close. From there simulation should show the best performance between >> varying the coils. >> >> Thanks - Dan > > Having trouble producing a good model Dan. NEC 2 indicates Qs which are > >5000, but no warnings or errors. I can run it in NEC 4.1, single, and > double precision, but I get over 400 warnings in the NEC output file; such > as: > > SEGCHK: WARNING - SEGMENTS 1 AND 271 CROSS AT A MIDPOINT WITH SEPARATION > LESS THAN THE SUM OF THEIR RADII > > SEGCHK: WARNING - THE CENTER OF SEGMENT 1 IS WITHIN THE VOLUME OF SEGMENT > 271 > > These warnings are particularly strange since, for example, absolute > segments 1 and 271 are almost 12" apart in the model. Will see what I can > do to correct the error. > > 73, > > Frank > > The code I am using is as follows: > > CM Inductor Q Calculation > CE > GH 1 300 1 12 6 6 6 6 0.3125 > GW 2 5 6 0 12 0 0 12 0.3125 > GW 3 10 0 0 12 0 0 0 0.3125 > GW 4 5 0 0 0 6 0 0 0.3125 > GS 0 0 0.025400 > GE 0 > EX 0 3 5 00 1 0 > FR 0 5 0 0 3.7 0.02 > LD 5 1 1 320 5.7001E7 > RP 0 181 1 1000 -90 90 1.00000 1.00000 > EN NEC-2 and NEC-4 have different formats for the GH 'card'. This is the NEC-2 format, which will be interpreted differently by NEC-4. See your NEC-4 documentation for the correct NEC-4 format. Roy Lewallen, W7EL Article: 222023 of rec.radio.amateur.antenna From: Big Rich Soprano Subject: Re: Younger Sister Caught In BathTub With Hidden Cam... 4295 [2/2] Date: Fri, 03 Mar 2006 03:41:15 -0500 Message-ID: References: This scr is a "Backdoor Server Program" according to AntiVir! Article: 222024 of rec.radio.amateur.antenna From: Big Rich Soprano Subject: Re: TEEN SISTER WITH DILDO XXX 7396 [2/2] Date: Fri, 03 Mar 2006 03:41:26 -0500 Message-ID: References: This scr is a "Backdoor Server Program" according to AntiVir! Article: 222025 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: 80m mobile antenna question Date: Fri, 03 Mar 2006 02:07:35 -0800 Message-ID: <120g5ba3toc9oc5@corp.supernews.com> References: <4239-4407B982-64@storefull-3253.bay.webtv.net> <4407d7ba$1_1@newsfeed.slurp.net> I'm afraid people are getting too hung up by trying to squeeze everything into various pigeon holes like "dipole" and "ground". You'll have to think beyond those narrow and poorly defined and understood categories and look at the basics of antenna operation in order to understand what's happening. The field radiated from a conductor is determined by two things: the amount of current on it, and the length of the path the current takes. Theorists have known this for well over a century. The most sophisticated antenna analysis programs break the current paths into very short pieces ("segments"), calculate the current on each piece, and then calculate the resulting field from the product of the current and the segment length. Fields from various parts of the conductors can cancel or reinforce to any degree. (Mathematically, they add vectorally.) If you don't or can't believe this, you needn't bother continuing. For those still reading, let's imagine a 16 foot vertical wire with a tiny 3.5 MHz signal generator at the center. This is known in textbooks as a "dipole", but how things behave aren't dictated by what we call them, so feel free to insist it's a "seagull", "pizza", "xfppftm", or whatever makes you comfortable. The signal generator has two terminals, and any generator must have equal currents in and out of its two terminals. If you don't or can't believe that, brush up on Kirchoff's current law. If that doesn't do it, there's no need to continue further. Let's suppose the generator is producing one amp RMS of RF current. If, say, 0.2 amp is flowing upward out of the top terminal at a given instant, 0.2 amp is flowing upward into the bottom terminal at the same instant. By inspection, one amp RMS is flowing upward in the vertical wire immediately above and below the generator. By a number of techniques, we can show that the current decreases nearly linearly from the center to the ends. That is, four feet from the center, either above or below the source, the current is 1/2 amp. At the antenna tips, the current is zero, which we should expect: there's nowhere for it to go. It should be obvious that the wire above the source is radiating the same field strength as the wire below the source -- for each little piece of the wire above the source there's a piece below the source carrying exactly the same current. And as it turns out, the fields from all parts of both wires add completely in phase directly broadside to the wire, and only partially in phase in other directions. So at least directly broadside, we can say that the contribution from each wire is equal and proportional to its total field strength. Ok, now let's make one of the wires "ground" and the other a "whip", because we like to do that, right? Let's call the top wire a "whip", and bottom load it. We add an inductor (very small, physically, to avoid adding another dimension to this analysis) between the signal generator's top terminal and its connection with the upper wire. We can make the inductor the proper value to make the upper wire/inductor self resonant if it were grounded, or we can make the inductor about twice as large to make the whole dipole resonant. It doesn't matter. Now let's see what happened to the radiation from the "whip" and "ground" wires. There's no change whatsoever! The currents are exactly the same as they were before, on both wires. They still taper from the center to the tips as before. They both radiate equally. All we've done is change the impedance seen by the generator. If you don't believe this, perhaps you can explain why they won't. Next, let's replace the lower wire with a cylinder like a tank, say 10 feet in diameter but still 8 feet high. What happens then? Surely it must now be "ground", and "ground" doesn't radiate, does it? Well, it does radiate. The one amp flowing into the bottom generator terminal spreads out radially over the top of the cylinder. Although the current density decreases as we move out from the center, the total current also decreases. If only the cylinder top was present and the rest of the cylinder missing, the current would drop to nearly zero at the edge. But because of the presence of the rest of the cylinder, the current at the edge drops to about half the value at the center. The half which remains flows down the cylinder sides. This would result in the field from the cylinder being about half the field from the "whip" if the current decreased to zero at the bottom of the cylinder as it does at the top of the whip. But the current along the sides of the cylinder doesn't drop to zero at the bottom of the walls because it can flow onto the bottom of the cylinder. The average current on the whip is 0.5 amp, and on the cylinder (from a model) about 0.35 amp, so the cylinder's field is about 3 dB less than that of the "whip". Not quite what most of envision when we think of a "ground". If we top load the whip with a 10 foot diameter top hat, its average current increases to about 0.9 amp. But its presence also reduces the amount of current drop from the center to the edge of the cylinder top due to mutual coupling. The end result is larger current along the cylinder sides and very nearly the same field strength ratio between the "whip" and cylinder. So far this analysis has taken place in free space. What happens if we put the cylinder bottom just above the ground, say six inches? Now, surely, the cylinder is "ground"! But the current still flows down the sides and radiates just like the old original vertical lower wire did. And putting the bottom close to ground increases the current along the sides! The coupling between the cylinder bottom and ground acts somewhat like a top hat does to a whip, and increases the average current. Instead of 0.35 amp, it increases to about 0.42. Now the cylinder's field is only about 1.5 dB less than that of the "whip". I hope this has encouraged at least a few people to think a little before declaring every conductor to be either an "antenna" or a "ground plane" and assuming that by doing so they'll somehow cause it to behave in some predetermined and only vaguely understood fashion. Roy Lewallen, W7EL Bill Turner wrote: > ORIGINAL MESSAGE: > > Dan Richardson wrote: > >> That may have some validity in the VHF and higher ranges, but on HF - >> particularly on 80 meters - a car body's size is a small fraction of a >> wavelength (as is the whip portion). Consequently the vehicle body >> acts like the one half of a dipole antenna. > > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > Q. How can a car body which is a "small fraction" of a wavelength act > like one half of a dipole? > > A. It can't. > > Q. Well, what does it do then? > > A. It acts like a short piece of wire leading from the bottom of the > whip to the actual ground plane, namely the earth itself. > > Q. Does that help any? > > A. Probably a little, but remember the piece of wire (the car body) is > only a few feet long. Not very much on 80 meters. > > Q. Thanks, I get it now. > > A. You're welcome. > > 73, Bill W6WRT Article: 222026 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: 80m mobile antenna question References: <4239-4407B982-64@storefull-3253.bay.webtv.net> <4407d7ba$1_1@newsfeed.slurp.net> <120fo85epbaj24d@corp.supernews.com> Message-ID: <44081617_4@newsfeed.slurp.net> Date: 3 Mar 2006 05:10:31 -0500 David G. Nagel wrote: > Actually it is acting as one half of a dipole. It is just a > non-resonant half of a dipole. Remember "di" means two. > > Dave WD9BDZ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ In a strict sense you are correct, but in the context here where one half of the dipole is an eight-foot whip and the other half is four feet of car body, we don't have much of an 80 meter antenna without the coupling from car body to earth ground. Bill, W6WRT Article: 222027 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: 80m mobile antenna question References: <4239-4407B982-64@storefull-3253.bay.webtv.net> <4407d7ba$1_1@newsfeed.slurp.net> <120g5ba3toc9oc5@corp.supernews.com> Message-ID: <44081a47_1@newsfeed.slurp.net> Date: 3 Mar 2006 05:28:23 -0500 Roy Lewallen wrote: > I hope this has encouraged at least a few people to think a little > before declaring every conductor to be either an "antenna" or a > "ground plane" and assuming that by doing so they'll somehow cause it > to behave in some predetermined and only vaguely understood fashion. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ A very good explanation, thank you Roy. However... in your example of the giant tin can in free space, the top of the tin can is acting like a ground plane, the side is acting like an antenna and the bottom is again acting like a ground plane, just as we have been saying. When this model is transferred to a car body, the bottom of the car, in addition to the above, is also acting like one plate of a capacitor coupling the signal to the earth below it, commonly known as "ground". If someone disagrees with this I believe we have a problem with semantics more than physics. In other words, we are arguing over nothing. Bill, W6WRT Article: 222028 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: 80m mobile antenna question References: <44053ca7_4@newsfeed.slurp.net> <1141235031.104775.60590@t39g2000cwt.googlegroups.com> <1OrNf.42759$X7.21026@bignews7.bellsouth.net> Message-ID: <18XNf.43429$H71.26540@newssvr13.news.prodigy.com> Date: Fri, 03 Mar 2006 13:02:53 GMT Scott wrote: > If I remember correctly, the higher the coil goes, doesn't its value > have to increase as well? If so, might the coil dimensions become a bit > too big to handle? The bigger the top hat, the smaller the required reactance. -- 73, Cecil http://www.qsl.net/w5dxp Article: 222029 of rec.radio.amateur.antenna From: "David G. Nagel" Subject: Re: 80m mobile antenna question Date: Fri, 03 Mar 2006 09:09:34 -0600 Message-ID: <120gn1hpd81lmaa@corp.supernews.com> References: <4239-4407B982-64@storefull-3253.bay.webtv.net> <4407d7ba$1_1@newsfeed.slurp.net> <120fo85epbaj24d@corp.supernews.com> <44081617_4@newsfeed.slurp.net> Bill Turner wrote: > David G. Nagel wrote: > > >>Actually it is acting as one half of a dipole. It is just a >>non-resonant half of a dipole. Remember "di" means two. >> >>Dave WD9BDZ > > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > In a strict sense you are correct, but in the context here where one > half of the dipole is an eight-foot whip and the other half is four > feet of car body, we don't have much of an 80 meter antenna without the > coupling from car body to earth ground. > > Bill, W6WRT No argument here Bill. The point I guess I was trying to make is that a dipole antenna system is two elements no matter what you make them of. I use a Hi Sierra screwdriver antenna on my Honda Element. Even though is is an impressive construct I don't harbor any illusions that it is an efficient radiator. The body of the car is longer than the length of the screwdriver, coil and whip. I have also used an Outbacker. Some say that is a good antenna for it type, I have not had that good of a result with it. Of course I am using my mobile for Civil Air Patrol and the Outbacker does not fit that frequency very well on the precut tuning jacks. I have found this thread to be interesting but I think that is had passed that point. I do not consider myself to be anything other than an interested amateur and always consider your comments with great interest. Thank you for your personal comments. Dave WD9BDZ Article: 222030 of rec.radio.amateur.antenna From: mcalhoun@ksu.edu Subject: Re: 80m mobile antenna question Date: 3 Mar 2006 09:36:51 -0600 Message-ID: References: <44053ca7_4@newsfeed.slurp.net> <1141235031.104775.60590@t39g2000cwt.googlegroups.com> <440674bf_3@newsfeed.slurp.net> <120d11fn5ontsb0@corp.supernews.com> Roy Lewallen, W7EL, typed: >I'm not sure why, but most amateurs don't seem to realize that the whip >....[snip].... >The best arrangement, as others have pointed out, is to mount the >antenna right at the center of the top of the car. This makes the car >....[snip].... Although my "evidence" is purely anecdotal, I've sure had good success on 80 meters with a pair of hamsticks mounted horizontally (one pointing forward and one backwards) about two feet above my picup cab (which has a metal "topper" behind the cab at essentially cab-top height). I've always assumed it was acting much like an NVIS dipole.... -- --Myron A. Calhoun. Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785) 539-4448 NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol) Article: 222031 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: 80m mobile antenna question Date: Fri, 3 Mar 2006 11:02:32 -0600 Message-ID: <17919-440876A8-95@storefull-3252.bay.webtv.net> References: Cecil, W5DXP wrote: "The only way to improve on that on 75m would be to mount a piece of sheet metal on fiberglas poles connected at ythe ends of both bumpers." Kraus gives some support to that idea. Cecil has the 3rd edition of "Antennas" In that edition, there is a "Disc antenna" on page 720 with some similarity to cecil`s suggestion. The "flush-disk" antenna, (d) in Figure 21-11 is said to be comparable to a 1/4-wave vertical in performance, but has no projection. It could be covered with a dielectric sheet, make no noise in the wind, and break out no fluorescent tubes in parking garages. But, at 75m, the 0.3 lambda dia. depression to contain it would measure 22.5 meters. That woud require a vehicle that was very large indeed. At VHF and UHF it could be very practical. Best regards, Richard Harrison, KB5WZI Article: 222032 of rec.radio.amateur.antenna From: Me Subject: Re: radar and health ? References: <8545c34b738aa8f3099fdd2334602bc0.99986@mygate.mailgate.org> <6qJNf.25805$8d1.12957@read1.cgocable.net> Message-ID: Date: Fri, 03 Mar 2006 18:56:38 GMT In article <6qJNf.25805$8d1.12957@read1.cgocable.net>, Jules wrote: > I think if it is too strong it will affect your eyes first, ears then > nerves/brain last. There are lots of safety precautions for wx radar on > aircraft and they are generally are under 10kw for small planes, x band > radar. Large jets, c band. Then there are fighter aircraft whose > targeting radar has been know to kill small animals around the runways. > But those are out of favour now, low power is in. > > > > Thierry wrote: > > Hi, > > > > I received this message from a colleague but I cannot answer him. I d > > not know these systems. > > Could you help me ? > > > > My company has installed a Radar Tower for Port survaillence. The tower > > is about 50 meter height on top of the of a 3 stories building roof and > > my office building just below the tower on the same level, 20 meter away > > from the tower. At the same time, the surrounding is my working area ( > > Jetty Terminal for ships loading and unloading activities ). I can say > > that I'll be around that area 12 hours a day for another 20 years. > > > > My question: > > > > Is it safe to work in that area???? > > > > Thanks in advance > > Thierry > > http://www.astrosurf.org/lombry > > > > > The basic facts are: Any commercial civilian Xband Radar will NOT even come close to approching FCC RF Radiation Biologic Health Maximum Radiation Power Densities even if you are right next to the antenna. You are more likely to get hurt by the rotating antenna hiting you in the head than from the RF Energy coming out of the antenna. Wx Radar on Commecrcial Aircraft usually are left in Standby Mode untill the aircraft has taxied onto the tarmac beside the active runway. Eve if they were activated, most xBand versions still don't have the Power Density one foot in front of the antenna to approch the FCC RF Radiation Biologic Health Maximum. Military Radars are a totally different beast altogether, and there are very strict operational rules for when they can be operated inside US Water and Airspace. Me Article: 222033 of rec.radio.amateur.antenna Date: Fri, 03 Mar 2006 14:07:04 -0500 From: jawod Subject: Non-theoretical, practical and probably stupid question Message-ID: <54f81$440893e2$42a1bfc2$25389@FUSE.NET> I'm getting ready to mount a dipole between two trees in my backyard. Both are large sycamores and I plan to have the dipole about 60 feet up (max). In an ARRL publication, there is a description of using a bow and arrow to get over the branch desired. This is the method I guess I'll try (can't climb these trees). Once I have the nylon fishing line over, I'll need to hoist up a nylon rope attached to a pulley attached to the antenna itself (I mean, of course, the support line attached to insulator). I can't figure a way to hoist all this up without, say, 120 feet of nylon rope in an inverted U plus the weighted support line attached to the antenna. Yes, I can use a slip knot but I still end up having 60 feet of rope draped from the tree. Should I find a way to cut the nylon rope near the branch? Just tie up the hanging rope? It seems necessary to "waste" as much as 60 feet of rope in either side. If I support the center insulator, then double that. Is there a better way? John PS, Sorry, I couldn't find a way to insert something with imaginary numbers (hi) Article: 222034 of rec.radio.amateur.antenna From: "Ron H" References: Subject: Re: Younger Sister Caught In BathTub With Hidden Cam... 4295 [2/2] Message-ID: Date: Fri, 3 Mar 2006 13:23:31 -0600 Now I am not an IT professional mind you but I used test files with the scr extension as "SCRipt" files. The operating system likes to grab them and just do as the text inside instructs it. I use OE and it would reject such files if I set it up to but being a curious fellow, I like to see what I am missing. K3PID "Big Rich Soprano" wrote in message news:j60g02tfv0an71gaspk5k30t2i9vgbitlt@4ax.com... > This scr is a "Backdoor Server Program" according to AntiVir! Article: 222035 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: 80m mobile antenna question Date: Fri, 03 Mar 2006 11:34:00 -0800 Message-ID: <120h6hb13r7b32b@corp.supernews.com> References: <4239-4407B982-64@storefull-3253.bay.webtv.net> <4407d7ba$1_1@newsfeed.slurp.net> <120g5ba3toc9oc5@corp.supernews.com> <44081a47_1@newsfeed.slurp.net> Bill Turner wrote: > Roy Lewallen wrote: > >> I hope this has encouraged at least a few people to think a little >> before declaring every conductor to be either an "antenna" or a >> "ground plane" and assuming that by doing so they'll somehow cause it >> to behave in some predetermined and only vaguely understood fashion. > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > A very good explanation, thank you Roy. > > However... in your example of the giant tin can in free space, the top > of the tin can is acting like a ground plane, the side is acting like > an antenna and the bottom is again acting like a ground plane, just as > we have been saying. When this model is transferred to a car body, the > bottom of the car, in addition to the above, is also acting like one > plate of a capacitor coupling the signal to the earth below it, > commonly known as "ground". If someone disagrees with this I believe we > have a problem with semantics more than physics. > > In other words, we are arguing over nothing. > > Bill, W6WRT I interpreted your comments and those by some others as claiming that radiation from the car is insignificant, and that it therefore isn't effectively part of the antenna. I attempted to show that this isn't generally true. I also showed that coupling to the ground actually increases radiation from the car. So either I've convinced you by my illustration, or I misinterpreted your earlier remarks. Roy Lewallen, W7EL Article: 222036 of rec.radio.amateur.antenna From: Dot Subject: Re: Non-theoretical, practical and probably stupid question Message-ID: References: <54f81$440893e2$42a1bfc2$25389@FUSE.NET> Date: Fri, 03 Mar 2006 14:21:38 -0500 On Fri, 03 Mar 2006 14:07:04 -0500, jawod wrote: >Is there a better way? Yep... rent a cherry picker for a couple of hours or find someone to climb the tree and affix your pulleys. Article: 222037 of rec.radio.amateur.antenna From: tclay@qmc.ph.msstate.edu Subject: Re: Non-theoretical, practical and probably stupid question Date: 03 Mar 2006 14:20:37 -0600 Message-ID: <87u0afnuui.fsf@qmc.ph.msstate.edu> References: <54f81$440893e2$42a1bfc2$25389@FUSE.NET> >It seems necessary to "waste" as much as 60 feet of rope in either >side. If I support the center insulator, then double that. > >Is there a better way? I'm not sure what the problem is, yes, it takes a bunch of rope if you can't climb the tree. I usually don't bother with pulleys as I prefer to get the antenna up as high as possible. You will lose 15-20 feet of height (or more) using a pulley compared to not. Tor N4OGW Article: 222038 of rec.radio.amateur.antenna From: Owen Duffy Subject: Caronlina Windom characterisation Message-ID: Date: Fri, 03 Mar 2006 20:59:01 GMT I am working with some guys on ambient noise measurement in a pre BPL scenario. They are using FSM ( http://www.vk1od.net/fsm/ ) to make field strength measurements using a known comms receiver and a Carolina Windom (CW). We need to form a view on the CW antenna system losses (radiator, ground reflection, isolator, matching unit, feedline, ATU. Has anyone built and calibrated NEC models for the CW, or have they measured reliably feedpoint impedance on the various bands. This is not a troll, and I don't want to excite a war over the claimed performance of the CW, I am not interested in anecdotal evidence or QSO evidence as to whether they "work". I see that there will be significant issues in modelling the "secret" components of the CW unless someone has worked out an RF equivalent circuit of those components (the isolator and matching unit). Thanks... Owen -- Article: 222039 of rec.radio.amateur.antenna From: Jules Subject: Re: radar and health ? References: <8545c34b738aa8f3099fdd2334602bc0.99986@mygate.mailgate.org> <6qJNf.25805$8d1.12957@read1.cgocable.net> Message-ID: Date: Fri, 03 Mar 2006 16:04:49 -0500 Me wrote: > The basic facts are: Any commercial civilian Xband Radar will NOT even > come close to approching FCC RF Radiation Biologic Health Maximum > Radiation Power Densities even if you are right next to the antenna. > You are more likely to get hurt by the rotating antenna hiting you > in the head than from the RF Energy coming out of the antenna. > Wx Radar on Commecrcial Aircraft usually are left in Standby Mode > untill the aircraft has taxied onto the tarmac beside the active runway. runway > Eve if they were activated, most xBand versions still don't have the > Power Density one foot in front of the antenna to approch the FCC RF > Radiation Biologic Health Maximum. > Military Radars are a totally different beast altogether, and there are > very strict operational rules for when they can be operated inside US > Water and Airspace. On my plane the radar is 7.6 kw (xband). The manual says not to use it on the ground especially around people. Also they have been know to cause some sort of sparking on metal so fuel trucks are to be avoided. Shop people are cautioned to make sure it is not emitting if in stby mode, some do. The display will say STBY, the antenna not panning, but it is emitting. Go figure. Small airplanes have xband not because it is wimpy but because of antenna size constraints. These are 10 ro 12 inch diameter "flat dish" antennas. Lots of waveguide-like openings on it. Extreemly directional. And this is a small 6 seater plane. Large weather radars, ground based are sband. Big antennas. In the late 80's many radars dropped down to under 10 watts. Most under one watt. Mainly due to improved signal processing. Even on large jets with large dishes. With the lower power came more managable attenuation affects in rain too. You do not want your head one foot away from my radar when it is on. And I wouln't let you try it, even if you asked. Article: 222040 of rec.radio.amateur.antenna From: "Frank's" References: Subject: Re: Caronlina Windom characterisation Message-ID: Date: Fri, 03 Mar 2006 21:15:19 GMT "Owen Duffy" wrote in message news:dtah025lldi6hjdk1asg4jcst8mo54oimq@4ax.com... > > I am working with some guys on ambient noise measurement in a pre BPL > scenario. > > They are using FSM ( http://www.vk1od.net/fsm/ ) to make field > strength measurements using a known comms receiver and a Carolina > Windom (CW). > > We need to form a view on the CW antenna system losses (radiator, > ground reflection, isolator, matching unit, feedline, ATU. > > Has anyone built and calibrated NEC models for the CW, or have they > measured reliably feedpoint impedance on the various bands. > > This is not a troll, and I don't want to excite a war over the claimed > performance of the CW, I am not interested in anecdotal evidence or > QSO evidence as to whether they "work". > > I see that there will be significant issues in modelling the "secret" > components of the CW unless someone has worked out an RF equivalent > circuit of those components (the isolator and matching unit). > > Thanks... > > Owen Owen, I have done some tentative modelling of the CW; how valid the model is, I am not sure. I used the "TL" card for the actual coaxial feedline, and ran a single wire from the antenna feed point to one side of the TL source segment. The idea was to replicate the coaxial surface current. I don't think the balun (Isolator) will have any effect on the antenna performance. I may even have the code saved someplace if anybody is interested. Why would you not use a calibrated EMC monopole for HF? Frank Article: 222041 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Caronlina Windom characterisation Message-ID: <6rdh02hso77p0mvmqj92rhnqr5dgv3hevb@4ax.com> References: Date: Fri, 03 Mar 2006 21:49:23 GMT On Fri, 03 Mar 2006 21:15:19 GMT, "Frank's" wrote: > >Owen, I have done some tentative modelling of the CW; how valid the model >is, I am not sure. I used the "TL" card for the actual coaxial feedline, >and ran a single wire from the antenna feed point to one side of the TL >source segment. The idea was to replicate the coaxial surface current. I >don't think the balun (Isolator) will have any effect on the antenna >performance. I may even have the code saved someplace if anybody is >interested. Why would you not use a calibrated EMC monopole for HF? Thanks Frank. Some thoughts... I think they call the thing at the top a matching unit, and it seems to be a 4:1 transformer, but I have no idea of its common mode impedance that is relevant to the model. Similarly the common mode impedance of the lower unit (Isolator) is relevant to the model, and of course the treatment of the main feedline (routing, where it is earthed). The loss in the vertical coax is probably relevant, and not adequately modelled in NEC. The loss in the main feedline and ATU are also relevant, and can be calculated from the feedpoint Z. If I were building a model, I would be thinking of the assymetric dipole with the generator at the "upper" feedpoint, a vertical wire to ground loaded where the matching unit and isolator are located, and loaded for an underground coax feed (as is the case in this installation). But, the model will depend heavily on the common mode impedance of the two proprietary boxes. Unless someone has measured these, or calibrated a model, the model results will be of limited value. Perhaps Roy will comment on the above. Owen -- Article: 222042 of rec.radio.amateur.antenna From: ml Subject: ftp 2m rig? Message-ID: Date: Sat, 04 Mar 2006 01:43:43 GMT hi I was wondering if anyone knew of any fairly current 2m or 2/440 rigs that allow programming access to the memories via means OTHER THAN 'cloaning' method? for example here are a few that i already know of tm700 tmv7 i am not sure about the most current rigs seems the web sites of the manuf don't really say any help is appreciated m Article: 222043 of rec.radio.amateur.antenna From: "Hal Rosser" References: <54f81$440893e2$42a1bfc2$25389@FUSE.NET> Subject: Re: Non-theoretical, practical and probably stupid question Message-ID: Date: Fri, 3 Mar 2006 21:14:07 -0500 "jawod" wrote in message news:54f81$440893e2$42a1bfc2$25389@FUSE.NET... > I'm getting ready to mount a dipole between two trees in my backyard. > Both are large sycamores and I plan to have the dipole about 60 feet up > (max). > > In an ARRL publication, there is a description of using a bow and arrow > to get over the branch desired. > > This is the method I guess I'll try (can't climb these trees). > Once I have the nylon fishing line over, I'll need to hoist up a nylon > rope attached to a pulley attached to the antenna itself (I mean, of > course, the support line attached to insulator). > > I can't figure a way to hoist all this up without, say, 120 feet of > nylon rope in an inverted U plus the weighted support line attached to > the antenna. Yes, I can use a slip knot but I still end up having 60 > feet of rope draped from the tree. Should I find a way to cut the nylon > rope near the branch? Just tie up the hanging rope? > > It seems necessary to "waste" as much as 60 feet of rope in either side. > If I support the center insulator, then double that. > Wasting 60 ft of line is cheaper than a cherry picker rental, or broken leg. I will usually tie the rope off by putting a couple of large nails within step-ladder distance from the ground - but higher than a kid can normally reach. Then if you need to lower it again, it may be possible. Article: 222044 of rec.radio.amateur.antenna From: Butch Magee Subject: Re: Younger Sister Caught In BathTub With Hidden Cam... 4295 [1/2] Date: Fri, 03 Mar 2006 21:02:32 -0600 Message-ID: <120i0qb41ith58e@corp.supernews.com> References: Ron H wrote: > I certainly hope everyone in this list is smart enough to NEVER open a file > with the .scr extension! > > > Carry On! > K3PID > Ron H. > > I don't mind my ignorance showing,...what is an .scr ext? KF5DE Article: 222045 of rec.radio.amateur.antenna From: jc Subject: Re: Concord Police Department Officer Ron Turner is a fucken dirty References: <1141434057.863204.9240@i39g2000cwa.googlegroups.com> Message-ID: Date: Fri, 03 Mar 2006 21:51:12 -0800 sananda@hotmail.com wrote: > Concord Police Department Officer Ron Turner is a fucken dirty black > pig cop > he stoped me because i had 820lbs. in a 1 ton pu truck > First the cop called for chp portable scale to get the > wt of my truck he could not get one then he had me > go to the chp truck scale on the hwy to get the wt of > my truck no one was there then he had me go to moving co. > and had me drive on there scale to get wt of my truck with > me in it . the scale said i was under 6000lbs. but he gave > me a ticket for overloaded tire load range . he added the > gross wt 6000lbs + 3042 tire load range for ea tire = 12168lbs > is 18168 - 6000 - 6000 = 12168lbs ticket said i was 12168lbs > over loaded. i had me 150lbs + 2 boxes 820lbs. in bed -in the > boxes was cardboard. just before he let me go he had me go > into the restroom at the moving co. and told me to strip with 2 > back up cops 1 male cop and 1 girl cop. and then he let me > go after 8 hours. got to court i showed him how to do the > math on the tire load range and he walks up to the judge and > says ALL CHARGES DROPPED. > > Ron tuner who is 300lb black dirty pig cop needs to go > hunting with dick cheney . > > > Toilets > Police employees in Concord, California, filed a $30 million > lawsuit against the Concord Police Department after they found > a hidden in the restroom. > You should see this problem from the prof truckdrivers point this crap has been going on for years. and people in CA wonder why stuff cost soo much in CA? try a $3000.00 ticket for a 10 minute infraction on a logbook want to see more than afew bad cop's go and see KERN county this seems to be the sweet spot where the a$$hole's hang.I mean serve and protect FWIW OTR trucker.......20 years + J.C. Article: 222046 of rec.radio.amateur.antenna From: Bob Miller Subject: Re: Caronlina Windom characterisation Message-ID: References: Date: Sat, 04 Mar 2006 04:11:07 GMT On Fri, 03 Mar 2006 20:59:01 GMT, Owen Duffy wrote: > >I am working with some guys on ambient noise measurement in a pre BPL >scenario. > >They are using FSM ( http://www.vk1od.net/fsm/ ) to make field >strength measurements using a known comms receiver and a Carolina >Windom (CW). > >We need to form a view on the CW antenna system losses (radiator, >ground reflection, isolator, matching unit, feedline, ATU. > >Has anyone built and calibrated NEC models for the CW, or have they >measured reliably feedpoint impedance on the various bands. > >This is not a troll, and I don't want to excite a war over the claimed >performance of the CW, I am not interested in anecdotal evidence or >QSO evidence as to whether they "work". > >I see that there will be significant issues in modelling the "secret" >components of the CW unless someone has worked out an RF equivalent >circuit of those components (the isolator and matching unit). > >Thanks... > >Owen Their catalog shows modelled patterns. Might be some NEC models available at the Radio Works web site. bob k5qwg Article: 222047 of rec.radio.amateur.antenna From: "Ralph Mowery" References: <120i0qb41ith58e@corp.supernews.com> Subject: Re: Younger Sister Caught In BathTub With Hidden Cam... 4295 [1/2] Message-ID: Date: Sat, 04 Mar 2006 04:28:29 GMT "Butch Magee" wrote in message news:120i0qb41ith58e@corp.supernews.com... > Ron H wrote: > > I certainly hope everyone in this list is smart enough to NEVER open a file > > with the .scr extension! > > > > > > Carry On! > > K3PID > > Ron H. > > > > > I don't mind my ignorance showing,...what is an .scr ext? > > KF5DE The .scr is usually the screen saver program extentions. They are exicutable programs just like the .exe programs. They can take over the computer and do almost anything. Good way to pass on a virus or worm or anything if the programmer does not want to really use them as a screen saver. Article: 222048 of rec.radio.amateur.antenna From: "Frank" References: <12058okq4o35l22@corp.supernews.com> <44031031.9050905@comcast.net> <8eFMf.6418$dg.3208@clgrps13> <1206ib348gjnb4@corp.supernews.com> <4403BF4F.80702@comcast.net> <1207oqqsdjk4eab@corp.supernews.com> <4403EA1D.4090802@comcast.net> <12082j8tknvfi05@corp.supernews.com> <120acppce6jle62@corp.supernews.com> <5JoNf.7747$Ui.2219@edtnps84> <440675EC.9070204@comcast.net> Subject: Re: antenna impedance - calculated 10 - 20 Ohms - measured 36 Ohms?? Message-ID: Date: Sat, 04 Mar 2006 05:11:20 GMT > Frank, > > I observed by playing with the relative inductor values on the vertical > segment and the radial elements that it was possible to move the relative > feedpoint. This supports tuning the antenna by either inductor. > > Reg's c_poise program predicts a 75 uH loading coil. > > I am excited with prospect of coil models. > > Thanks - Dan Dan, I have done some minor approximations with your coil. I took the length and diameter to be 12", rather than 300 mm (11.8"). The coil copper pipe diameter is, as specified, 5/16" (0.3125"). I was a little confused with your use of the term "Pitch" as 0.5". In the sense of a screw thread pitch is the distance between adjacent thread peaks, but I took it to mean the actual distance between the outer walls of the pipe; in which case the actual pitch is 0.8125". If this is the case the total pipe length is just over 47 ft. The inductance calculates to 54.2uH, and the Q = 2990. I have not yet run the program in NEC 4, for greater accuracy, since I would like to get the model as close as possible in NEC 2. If I have gotten the pitch definition wrong then the model dimensions will violate the NEC criteria of the minimum distance between adjacent turns. The code for this preliminary run is shown below. Some of the odd-ball dimensions are just to approximately equalize segment lengths. Despite some of the weirdness of 4nec2, concerning "GH" cards, you should be able to run it. Frank CM Inductor Q Calculation CE GH 1 300 0.8125 12 6 6 6 6 0.15625 GW 2 3 0.72322 -5.95625 12 .35542 0 12 0.15625 GW 3 6 .35542 0 12 .35542 0 0 0.15625 GW 4 3 .35542 0 0 6 0 0 0.15625 GS 0 0 0.025400 GE 0 EX 0 3 3 00 1 0 FR 0 5 0 0 3.7 0.02 LD 5 1 1 312 5.7001E7 RP 0 181 1 1000 -90 90 1.00000 1.00000 EN Article: 222049 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Caronlina Windom characterisation Message-ID: References: Date: Sat, 04 Mar 2006 05:20:36 GMT On Sat, 04 Mar 2006 04:11:07 GMT, Bob Miller wrote: >Their catalog shows modelled patterns. Might be some NEC models >available at the Radio Works web site. Bob, I saw that, but did not find links to model files. Owen -- Article: 222050 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Question for Roy (was Re: 80m mobile antenna question) References: <4239-4407B982-64@storefull-3253.bay.webtv.net> <4407d7ba$1_1@newsfeed.slurp.net> <120g5ba3toc9oc5@corp.supernews.com> <44081a47_1@newsfeed.slurp.net> <120h6hb13r7b32b@corp.supernews.com> Message-ID: <4409280f_2@newsfeed.slurp.net> Date: 4 Mar 2006 00:39:27 -0500 Roy, your analogy of the car body as a tin can really got me to thinking. With the whip mounted dead center on the top of the car, I can see how the roof acts like a ground plane (a very short one) but I'm puzzled about the radiation from the lower part of the car body. If one visualizes RF flowing through the sides, hood and trunk of the car, the currents will all be in phase with each other (roughly, of course) but the currents are displaced in space by several feet. How does this affect the net radiation from the car body as a whole? Is there some addition or subtraction due to having the same current, same phase but at a different location in space, and arranged in a more or less 360 degree pattern? An interesting thought. 73, Bill W6WRT Article: 222051 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: Concord Police Department Officer Ron Turner is a fucken dirty black pig cop References: <1141434057.863204.9240@i39g2000cwa.googlegroups.com> Message-ID: <44092970$1_2@newsfeed.slurp.net> Date: 4 Mar 2006 00:45:20 -0500 ORIGINAL MESSAGE: Anonymous wrote: > Contact a lawyer. And then see a psychiatrist. > > On second thought, see a psychiatrist and THEN contact a lawyer. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ On third thought, just see the psychiatrist. After you're cured, he might even explain what the "antenna" in this group's name is all about. Bill T. Article: 222052 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: Concord Police Department Officer Ron Turner is a fucken dirty black pig cop References: <1141434057.863204.9240@i39g2000cwa.googlegroups.com> Message-ID: <44092a6d$1_1@newsfeed.slurp.net> Date: 4 Mar 2006 00:49:33 -0500 ORIGINAL MESSAGE: jc wrote: > try a $3000.00 ticket for a 10 minute infraction on a logbook ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Try a million dollar lawsuit over permanent disability because some dumb trucker kept on driving and fell alseep. Serves you right. Bill T. Article: 222053 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Question for Roy (was Re: 80m mobile antenna question) Date: Fri, 03 Mar 2006 22:31:49 -0800 Message-ID: <120id2o6n2b1od9@corp.supernews.com> References: <4239-4407B982-64@storefull-3253.bay.webtv.net> <4407d7ba$1_1@newsfeed.slurp.net> <120g5ba3toc9oc5@corp.supernews.com> <44081a47_1@newsfeed.slurp.net> <120h6hb13r7b32b@corp.supernews.com> <4409280f_2@newsfeed.slurp.net> Think for a moment about a wire carrying RF current. RF current in any good conductor stays very close to the surface, so it's valid to imagine it flowing right on the surface. On a wire, the current spreads uniformly around the wire (unless it's very close to some other conductor), and each little part radiates. But at any distant point, the fields from the currents at various places around the wire (at a single location along the wire) are virtually the same, so it acts like a single current filament flowing on an infinitesimally thin wire. This is, in fact, how NEC and similar programs model conductor currents. The same even spreading happens as the wire gets fatter and fatter, but only up to a point. The model of a single current filament begins breaking down when the fields from different places around the wire are noticeably different at a distant point. This happens when the wire diameter becomes an appreciable fraction of a wavelength. Other things happen, then, too -- circumferential currents -- ones flowing around the wire -- develop, resulting in (or being caused by, depending on your point of view) non-uniform current distribution around the wire. And the wire itself affects the field. That is, the current on the side away >from a distant point can't directly radiate to the distant point because the wire is in the way. Because the various current contributions around the wire won't all add together at a distant point any longer, the pattern changes. I can't give any more specific answer to the question, really, than that the pattern will become more complex. In the case of the example I gave earlier with the cylindrical "car", if you raise the frequency, you'll reach a point where these effects happen. One result will be that the horizontal pattern will no longer be omnidirectional, but develop lobes. The height of the cylinder or car might affect the way current is distributed around it -- I haven't thought about it enough to hazard a guess. The good news is that today's modeling programs do a good job of showing these effects. The general technique is to represent flat surfaces such as a car top or side as a wire grid, to stay within the program's requirements that wire diameter must be no more than a very small fraction of a wavelength. As long as the holes in the grid are kept to a tenth of a wavelength or less, results are quite good. Roy Lewallen, W7EL Bill Turner wrote: > Roy, your analogy of the car body as a tin can really got me to > thinking. > > With the whip mounted dead center on the top of the car, I can see how > the roof acts like a ground plane (a very short one) but I'm puzzled > about the radiation from the lower part of the car body. If one > visualizes RF flowing through the sides, hood and trunk of the car, the > currents will all be in phase with each other (roughly, of course) but > the currents are displaced in space by several feet. > > How does this affect the net radiation from the car body as a whole? Is > there some addition or subtraction due to having the same current, same > phase but at a different location in space, and arranged in a more or > less 360 degree pattern? > > An interesting thought. > > 73, Bill W6WRT Article: 222054 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: Question for Roy (was Re: 80m mobile antenna question) References: <4239-4407B982-64@storefull-3253.bay.webtv.net> <4407d7ba$1_1@newsfeed.slurp.net> <120g5ba3toc9oc5@corp.supernews.com> <44081a47_1@newsfeed.slurp.net> <120h6hb13r7b32b@corp.supernews.com> <4409280f_2@newsfeed.slurp.net> <120id2o6n2b1od9@corp.supernews.com> Message-ID: <44097625_3@newsfeed.slurp.net> Date: 4 Mar 2006 06:12:37 -0500 Thanks, Roy. Interesting. 73, Bill W6WRT Article: 222055 of rec.radio.amateur.antenna From: subdude Subject: Re: Concord Police Department Officer Ron Turner is a fucken dirty black pig cop Message-ID: References: <1141434057.863204.9240@i39g2000cwa.googlegroups.com> Date: Sat, 04 Mar 2006 14:54:29 GMT On Fri, 03 Mar 2006 21:51:12 -0800, jc graced us with: >sananda@hotmail.com wrote: >> Concord Police Department Officer Ron Turner is a fucken dirty black >> pig cop >> he stoped me because i had 820lbs. in a 1 ton pu truck >> First the cop called for chp portable scale to get the >> wt of my truck he could not get one then he had me >> go to the chp truck scale on the hwy to get the wt of >> my truck no one was there then he had me go to moving co. >> and had me drive on there scale to get wt of my truck with >> me in it . the scale said i was under 6000lbs. but he gave >> me a ticket for overloaded tire load range . he added the >> gross wt 6000lbs + 3042 tire load range for ea tire = 12168lbs >> is 18168 - 6000 - 6000 = 12168lbs ticket said i was 12168lbs >> over loaded. i had me 150lbs + 2 boxes 820lbs. in bed -in the >> boxes was cardboard. just before he let me go he had me go >> into the restroom at the moving co. and told me to strip with 2 >> back up cops 1 male cop and 1 girl cop. and then he let me >> go after 8 hours. got to court i showed him how to do the >> math on the tire load range and he walks up to the judge and >> says ALL CHARGES DROPPED. >> >> Ron tuner who is 300lb black dirty pig cop needs to go >> hunting with dick cheney . >> >> >> Toilets >> Police employees in Concord, California, filed a $30 million >> lawsuit against the Concord Police Department after they found >> a hidden in the restroom. >> > >You should see this problem from the prof truckdrivers point >this crap has been going on for years. >and people in CA wonder why stuff cost soo much in CA? >try a $3000.00 ticket for a 10 minute infraction on a logbook >want to see more than afew bad cop's go and see KERN county this seems >to be the sweet spot where the a$$hole's hang.I mean serve and protect >FWIW >OTR trucker.......20 years + >J.C. Worked in the industry for 15 years, as a consultant then as a General Manager of a freight forwarding firm in DTW. Not only did I do the occaisional ride along for QA, but also had to discipline a number of truckers for log infractions. Most truckers are required only to do 2 things - drive and follow the rules. Maintaining logs is a small part of the latter - and necessary to protect other drivers on the road. Christ, in my day you had to load and unload the trucks on LTL deals, now they don't even do that. And BTW, I'd *STILL* rather pay more than risk more. So stop whining; if the job is too difficult go work for Mc D's... Article: 222056 of rec.radio.amateur.antenna From: "Allan W. Bart, Jr." Subject: Errors in Wilfred Caron Smith Chart Book Message-ID: <2RjOf.253$eJ1.142@trndny05> Date: Sat, 04 Mar 2006 17:09:18 GMT Hello, I have owned the book for about 15 years and now I am hearing aout errors. does anyone have a list of them? AB Article: 222057 of rec.radio.amateur.antenna From: Me Subject: Re: radar and health ? References: <8545c34b738aa8f3099fdd2334602bc0.99986@mygate.mailgate.org> <6qJNf.25805$8d1.12957@read1.cgocable.net> Message-ID: Date: Sat, 04 Mar 2006 18:18:55 GMT In article , Jules wrote: > Me wrote: > > > The basic facts are: Any commercial civilian Xband Radar will NOT even > > come close to approching FCC RF Radiation Biologic Health Maximum > > Radiation Power Densities even if you are right next to the antenna. > > You are more likely to get hurt by the rotating antenna hiting you > > in the head than from the RF Energy coming out of the antenna. > > Wx Radar on Commecrcial Aircraft usually are left in Standby Mode > > untill the aircraft has taxied onto the tarmac beside the active runway. > runway > > Eve if they were activated, most xBand versions still don't have the > > Power Density one foot in front of the antenna to approch the FCC RF > > Radiation Biologic Health Maximum. > > Military Radars are a totally different beast altogether, and there are > > very strict operational rules for when they can be operated inside US > > Water and Airspace. > > On my plane the radar is 7.6 kw (xband). The manual says not to use it > on the ground especially around people. Also they have been know to > cause some sort of sparking on metal so fuel trucks are to be avoided. > Shop people are cautioned to make sure it is not emitting if in stby > mode, some do. The display will say STBY, the antenna not panning, but > it is emitting. Go figure. Small airplanes have xband not because it is > wimpy but because of antenna size constraints. These are 10 ro 12 inch > diameter "flat dish" antennas. Lots of waveguide-like openings on it. > Extreemly directional. And this is a small 6 seater plane. > > Large weather radars, ground based are sband. Big antennas. > > In the late 80's many radars dropped down to under 10 watts. Most under > one watt. Mainly due to improved signal processing. Even on large jets > with large dishes. With the lower power came more managable attenuation > affects in rain too. > > You do not want your head one foot away from my radar when it is on. And > I wouln't let you try it, even if you asked. > > > Jules, you really need to go back to Radar School and try and understand the technology that your using. 7.6Kw Pulsed Xband Radars have an AVERAGE Power of less than 20 watts. It isn't the Peak Pulse Power that fries you, or causes the sparks, it is the AVERAGE Power, and less than 20 watts one foot in front of ANY antenna is considerably less than that, due to RF Radiation being subject to the Inverse Square Law. Most of the old Decca 20Kw Commercial Marine Radars in xBand had Average Powers less that 35 watts, and were well below maximum Radiation Power Densities directly in from of the 6ft Slotline Antennas. Your socalled Flat Dish antennas at nothing more than a tuned Phase Array, and again, one foot out in front, Power Densities are well below maximum permissable Power Densities. Third Generation Commercial xBand Radar Technology, that came in the 80's, introduced Solid State LNA's, Ring Circulating Isolators, and Logrythemic IF ampilfiers, which improved the receivers Noise Figures, and Dynamic Gain by an Order of Magnitude. This is all in the RF Path, and had nothing to do with signal processing of baseband signals which didn't come into play untill DSP Processors were intoduced in the mid 90's and the Fourth Generation of Commercial Radars. Manuals are written by folks who understand the technology, about as much as the lawyers, that approve them before they are published. Yes, there are safety concerns with radar operations around FBO Fueling Operations, but the incidents of actual causal problems, are rare to the extreme. Again, all the above is TRUE only for commercial radars, and may, or may not be TRUE, and likely NOT TRUE for Military Radars, as these are more often than not CW operating, and, or doppler type radars that are NOT Pulsed. Me Article: 222058 of rec.radio.amateur.antenna From: Jim Chandler Subject: Re: Concord Police Department Officer Ron Turner is a fucken dirty References: <1141434057.863204.9240@i39g2000cwa.googlegroups.com> Message-ID: Date: Sat, 04 Mar 2006 18:38:44 GMT sananda@hotmail.com wrote: > Concord Police Department Officer Ron Turner is a fucken dirty black > pig cop > he stoped me because i had 820lbs. in a 1 ton pu truck > First the cop called for chp portable scale to get the > wt of my truck he could not get one then he had me > go to the chp truck scale on the hwy to get the wt of > my truck no one was there then he had me go to moving co. > and had me drive on there scale to get wt of my truck with > me in it . the scale said i was under 6000lbs. but he gave > me a ticket for overloaded tire load range . he added the > gross wt 6000lbs + 3042 tire load range for ea tire = 12168lbs > is 18168 - 6000 - 6000 = 12168lbs ticket said i was 12168lbs > over loaded. i had me 150lbs + 2 boxes 820lbs. in bed -in the > boxes was cardboard. just before he let me go he had me go > into the restroom at the moving co. and told me to strip with 2 > back up cops 1 male cop and 1 girl cop. and then he let me > go after 8 hours. got to court i showed him how to do the > math on the tire load range and he walks up to the judge and > says ALL CHARGES DROPPED. > > Ron tuner who is 300lb black dirty pig cop needs to go > hunting with dick cheney . > > > Toilets > Police employees in Concord, California, filed a $30 million > lawsuit against the Concord Police Department after they found > a hidden in the restroom. > Well, for your information, Moron, you DO NOT add the tire load range to the gross weight. The gross weight is the absolute maximum that the vehicle is designed for. The tire load range is the weight that the tire is designed to carry and have a margin for safety. The one ton pickup's maximum gross weight would be the EMPTY weight of the vehicle plus the 2000 poun