Subject: GLOWBUGS digest 493

From: [email-masked]
Date: Wed, 2 Apr 1997 00:38:43 GMT

GLOWBUGS Digest 493

Topics covered in this issue include:

  1) Re: hum hum hummmmmmmm
	by [email-masked]
  2) Re: hum hum hummmmmmmm
	by Bob Roehrig <[email-masked]>
  3) Re: hum hum hummmmmmmm
	by Dan Cox <[email-masked]>
  4) Re: Look Ma, no Xfmr! (was Re: The 6T9'er)
	by Dan Cox <[email-masked]>
  5) 811a's
	by Dan Cox <[email-masked]>
  6) Re: Look Ma, no Xfmr! (was Re: The 6T9'er)
	by [email-masked] (michael silva)
  7) Re: Look Ma, no Xfmr! - hot chassis/bypass caps
	by Bob Roehrig <[email-masked]>
  8) Re: Look Ma, no Xfmr! (was Re: The 6T9'er)
	by Bob Roehrig <[email-masked]>
  9) Re: Look Ma, no Xfmr! (was Re: The 6T9'er)
	by Dan Cox <[email-masked]>
 10) RE: Regen. rcvr sensitivity
	by Sandy W5TVW <[email-masked]>
 11) Drake info
	by "Steve, N2MNN" <[email-masked]>

----------------------------------------------------------------------

Date: Mon, 31 Mar 1997 20:35:43 -0500 (EST)
From: [email-masked]
To: [email-masked], [email-masked]
Subject: Re: hum hum hummmmmmmm
Message-ID: <[email-masked]>

I too had a hum problem when I built an AC supply for my regen receiver.  
At first I thought that I could use a huge cap (about 200 uF) to snuff 
out any hint of ripple but alas, all I could hear out of the receiver was 
a raspy hum.  The raspy hum it turns out was caused by the silicon 
rectifiers I was using.  The harmonics from the noise that silicon 
rectifiers make as they switch can extend well into the HF area.  The 
solution to the silicon switching problem is to bypass the diodes with 
.01 uF caps.  This solved the raspy hum but a more familiar 60 Hz hum 
remained.

I tired many things to get rid of the 60 Hz hum but, it finally took some 
iron to knock it out.  I used the primary of a audio output transformer 
but any filter choke would work.  BTW, the inductance of the audio choke 
was around 5 Hy.

I have heard that the AC on the heaters can also be a source of hum but, 
since I used a battery for the heater supply on my receiver, I didn't 
have that problem.

73,  Eric  WD6DGX

------------------------------

Date: Mon, 31 Mar 1997 21:02:31 -0600 (CST)
From: Bob Roehrig <[email-masked]>
To: Leon Wiltsey <[email-masked]>
Cc: Multiple recipients of list <[email-masked]>
Subject: Re: hum hum hummmmmmmm
Message-ID: <[email-masked]>

On Mon, 31 Mar 1997, Leon Wiltsey wrote:

> The ripple on my b+ is .35v and it drive the 6sl7
> nicely so I have hum.  Am using 75 mfd caps in filter now,
> Wish the det put out a larger sig.  The most I can get
> out of it is .25vac using my sig ben with mod. on.  If the det
> output was higher I would not have a problem.  Trying different
> voltages on 6aq5 det make no real diff in output.

I looked at my regen tonight and made some measurements.  On a good
CW signal on 80 meters, I get about 500mv P-P signal at the detector
output. The detector is a 6AU6. Circuit is a Hartley. Regen controlled
with a screen pot between B+ and ground. Plate supply is 125V. Screen
voltage on the edge of regen is 30V. 

Plate supply uses an isolation transformer. Full wave diode bridge.
FIlter is three 40 uf caps. Between cap 1 and 2 I have a small choke,
which I never measured but is not doing a whole lot of good. Input
ripple is 2V P-P, across cap 2 I have 750mv P-P ripple. That point
feeds B+ to the audio stage (a 6AK6). Between filter caps 2 and 3
I have a 2.2K resistor. B+ for the detector taken from cap 3.
Ripple there is only 20mv P-P. 

Filament power obtained from 6.3VAC transformer with center tap
grounded. I agree with someone else - if you don't have a center tap
to ground, then use a 100 ohm pot across the filaments with the wiper
to ground. 

I suggest that if you don't have a filter choke, then try the primary
of a small filament transformer.

        E-mail [email-masked]           73 de Bob, K9EUI
            CIS: Data / Telecom   Aurora University, Aurora, IL
                      630-844-4898  Fax 630-844-5530

------------------------------

Date: Mon, 31 Mar 1997 19:27:10 +0000
From: Dan Cox <[email-masked]>
To: [email-masked]
Subject: Re: hum hum hummmmmmmm
Message-ID: <[email-masked]>

Leon Wiltsey wrote:

  The ripple on my b+ is .35v and it drive the 6sl7
  nicely so I have hum.  Am using 75 mfd caps in filter now,
  Wish the det put out a larger sig.  The most I can get
  out of it is .25vac using my sig ben with mod. on.  If the det
  output was higher I would not have a problem.  Trying different
  voltages on 6aq5 det make no real diff in output.

  Thank the good LORD for all that you have!!!

  Leon B Wiltsey jr. (Lee)

  68yr old semi disabled senior
  (stroke got my balance and coordination)
  play keyboard and sing
  music 1920's to 60'
  none of the 80'S- 90'S noise

 Have you tried a filter reactor/choke in your high voltage supply?
Also you might look for capacitors that are inductive in the supply as
they can cause motorboating and hum from regeneration.

------------------------------

Date: Mon, 31 Mar 1997 19:32:52 +0000
From: Dan Cox <[email-masked]>
To: [email-masked]
Subject: Re: Look Ma, no Xfmr! (was Re: The 6T9'er)
Message-ID: <[email-masked]>

  Brian,

    Yes I have an isolation transformer good to 200 watts as well as a
90 watter.  They ARE a GOOD thing to have!  I got buzzed on a heathkit
that had bad bypasses from the ac to ground.  I touched ground and the
chassis and guess what happened?  YOWWWWOWWW*&^%$##$$!!
But I'm much better now.

P.S  What's wrong with chasing spaceships behind comets?  Doesn't
everyone?
Dan :)

------------------------------

Date: Mon, 31 Mar 1997 19:38:21 +0000
From: Dan Cox <[email-masked]>
To: [email-masked]
Subject: 811a's
Message-ID: <[email-masked]>

  I have to attest to 811a ruggedness.  I was working on an amp the
  othe night with two of them in it at about 1500 volts.  Grounded
  grid.  WITHOUT the grids grounded!:(  Blew the emulsion coating
  right off the plate of one tube.  BUT it still functions great and
  runs fine(real shiny though).  Stupid mistake but saved by rugged
  tubes.

------------------------------

Date: Mon, 31 Mar 1997 23:18:51 -0600 (CST)
From: [email-masked] (michael silva)
To: [email-masked]
Subject: Re: Look Ma, no Xfmr! (was Re: The 6T9'er)
Message-ID: <[email-masked]>

Brian wrote: 
>
>Dan, Cory and Michael.
>
>I challenge you all to look for at least an ISOLATION transformer!!

Not a problem here -- I've got four of various sizes.
>
>For safety's sake, you really would be better off...

Ah, but is this really true in the situation I questioned?  How much 
danger *is* there with a three-wire GFI-protected outlet?  Might this 
fear not be a misplaced leftover from the days of non-protected, 
non-polarized plugs?  As Dan related, you can get also get hit due to 
bad AC line caps, as well as winding-to-core shorts and miscellaneous 
foul-ups.  I'm still waiting for a definitive answer as to why this 
would be a Bad Thing To Do.

73,
Mike, KK6GM

------------------------------

Date: Tue, 1 Apr 1997 08:18:42 -0600 (CST)
From: Bob Roehrig <[email-masked]>
To: Dan Cox <[email-masked]>
Cc: Multiple recipients of list <[email-masked]>
Subject: Re: Look Ma, no Xfmr! - hot chassis/bypass caps
Message-ID: <[email-masked]>

I mentioned some time back that I HATE AC LINE BYPASS CAPS!
In much equipment, these caps are way too large and pass way
too much current. Even if they are good, they will trip GFI
breakers. If you insist on having line bypass aps in your gear,
replace the existing ones with .001 caps at the highest voltage
you can obtain (like 1000V). If you have the chassis grounded,
these caps don't really do much good IMHO.

        E-mail [email-masked]           73 de Bob, K9EUI
            CIS: Data / Telecom   Aurora University, Aurora, IL
                      630-844-4898  Fax 630-844-5530

------------------------------

Date: Tue, 1 Apr 1997 08:31:19 -0600 (CST)
From: Bob Roehrig <[email-masked]>
To: michael silva <[email-masked]>
Cc: Multiple recipients of list <[email-masked]>
Subject: Re: Look Ma, no Xfmr! (was Re: The 6T9'er)
Message-ID: <[email-masked]>

tOn Tue, 1 Apr 1997, michael silva wrote:

> Ah, but is this really true in the situation I questioned?  How much 
> danger *is* there with a three-wire GFI-protected outlet?

If you use a 3-wire cord, if you fuse the hot side at the entrance 
to the chassis, if you isolate the neutral from the chassis (you should
not have ground and neutral tied together), if the chassis is tied to
the ground lead, then the setup should not be a problem.

        E-mail [email-masked]           73 de Bob, K9EUI
            CIS: Data / Telecom   Aurora University, Aurora, IL
                      630-844-4898  Fax 630-844-5530

------------------------------

Date: Tue, 01 Apr 1997 12:49:39 +0000
From: Dan Cox <[email-masked]>
To: [email-masked]
Subject: Re: Look Ma, no Xfmr! (was Re: The 6T9'er)
Message-ID: <[email-masked]>

    I'm still waiting for a definitive answer as to why this
  would be a Bad Thing To Do.

  73,
  Mike, KK6GM

  As long as the chassis is the grounded side then I don't really see a
problem. I guess doing it this way just has a deathly air to it(to some
people), that's all. :)
Dan, KD6NXI

------------------------------

Date: Tue, 1 Apr 1997 23:19:07 +0000
From: Sandy W5TVW <[email-masked]>
To: [email-masked]
Subject: RE: Regen. rcvr sensitivity
Message-ID: <19970401231906.AAA18558@LOCALNAME>

        I made some quick checks on my two active receivers and came up with
the following:

        National 2DCSW-3 receiver (model 2).  Uses a '32 TRF stage, '32
detector, '30 AF amp.  Sensitivity spot checked and found as below.
        Mhz             CW              AM
        1.6             3 uv.           12uv.
        3.5             1-2 uv.         10 uv.
        7.0             1-2uv.          10 uv.
        14              2 uv             12 uv.
        21              2-3 uv          12-14 uv        

        Tried bandspread and general coverage coil sets.  No difference
except better stability with bandspread sets.  "AM" sensitivity measured
just below oscillation point
with generator 30% modulated.

        Homebrew one tube set.  Uses a single 1J6G tube (Same as the '19
except for
base) dual triode.  One stage detector one stage AF amp.

        Mhz.            CW              AM
        3.5               3-4 uv.       15-20 uv.

        Same test conditions as above.  Generator used was a General Radio
1001A terminated with 50 adapter and 50 ohm termination.

73,

E. V. Sandy Blaize, W5TVW
"Boat Anchors collected, restored, repaired, traded and used!"
417 Ridgewood Drive,
Metairie, LA., 70001
[email-masked]
**Looking for:  860 tubes, WL-460 tubes, RK-18,20,28 tubes**
**Butternut HF2V antenna, G-R test gear.....................***

------------------------------

Date: Tue, 1 Apr 1997 17:43:54 -0500
From: "Steve, N2MNN" <[email-masked]>
To: [email-masked]
Subject: Drake info
Message-ID: <[email-masked]>

Hello all,

I think I am leaning towards the purchase of a Drake receiver and
transmitter pair, and would like to obtain more info on the different models
that were made.  Does anyone know of the existence of a list on the Internet
just for Drake owners?

Thanks,

Steve, N2MNN
[email-masked]

------------------------------

End of GLOWBUGS Digest 493
**************************