Subject: GLOWBUGS digest 253

From: [email-masked]
Date: Sun, 4 Aug 1996 17:56:53 -0500 (CDT)

GLOWBUGS Digest 253

Topics covered in this issue include:

  1) Another One-Tube Superhet Wonder
	by [email-masked]
  2) What a great day...
	by Chris Broadbent <[email-masked]>
  3) Re: What a great day...
	by [email-masked] (Michael Herr)
  4) Ye Olde Valves - Electrical Equivalents?
	by [email-masked]

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Date: Sat, 03 Aug 1996 22:42:09 -0500 (EST)
From: [email-masked]
To: [email-masked]
Subject: Another One-Tube Superhet Wonder
Message-ID: <[email-masked]>

Came across an interesting one-tube AM superhetrodyne receiver circuit
called the "Minidyne" in Popular Electronics, Sep 1956.  This one is a
bit different from the "one-tubers" built around compactrons in that it
uses a 9-pin miniature, a 6U8, and a passive mixer.  Here's the circuit
in a nutshell.

The signal is picked up by a ferrite loop antenna tuned by the 365 mmfd
RF section of a dual variable condenser.  A low-impedance tap feeds a
germanium diode mixer which then feeds the low-impedance side of a 455
kc IF transformer (a type designed for use in sand-state circuits - in
this circuit it's used "backwards") which is in series with a low
impedance take-off winding of the LO coil which is tuned by the LO
section of the dual variable condenser.  The 6U8 triode functions as the
LO.  The IF signal is amplified by the pentode 6U8 section feeding a
diode-output IF transformer with a germanium diode detector in series
with the IF secondary.  The AF signal appears across a 1 Meg volume
control and is fed back to the pentode section which doubles as an AF
amplifier (this is the classical "Reflex" amplifier).  The AF output is
developed across a universal output transformer whose primary is in
series with the IF output transformer primary and whose secondary
directly feeds a loudspeaker.

An interesting "minimalist" circuit and a good way to use up all those
"pesky" 6U8s!  This one's definitely going into the winter project
queue.  My only concern is that there could be significant LO radiation
if an external antenna is connected to the input.  I'll send out
photocopies of the article to anyone who sends a SASE - 32 cents should
do it - non-USA requesters don't need to worry about the stamp.

/-------------------------------------------\
| Michael A. Burke              THIS SPACE  |
| Synetics Consultants           FOR RENT   |
| PO Box 439, 11 Scenic Dr      REAL CHEAP! |
| Westminster, MA 01473                     |
| 508-874-0908           |/===\|            |
| [email-masked]        {}(0|0){}           |
|---------------------ooOO-(_)-OOoo---------|
|                                           |
| Do unto others as they would be done unto |
|   and practice random acts of kindness.   |
\___________________________________________/

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Date: Sat, 3 Aug 1996 21:42:26 -0500 (CDT)
From: Chris Broadbent <[email-masked]>
To: [email-masked]
Subject: What a great day...
Message-ID: <[email-masked]>

I must apologise for using the glowbugs distribution for this, but I can't
help it.  Today my wife and I went to the Austin Ham Meet at the Omni Hotel.
We went just to look for surplus stuff and what-have-you.  As some of you
might know by now, I have been working on the design of a Tube based CW TX,
at the same time as studying the code and theory necessary for at least a
novice license.  They held tests at the Meet today.  I was aiming more at
the end of this month for my attempt.  However, after determining that I had
nothing to lose (other than $6.05), I figured, "what the hey...".

To cut this already too long story short, I am now the owner of two
certificates of successful completion - one for 5WPM and one for the Novice
and Tech theory components.  So when I get my license, I'll be a Tech+.

I'm quite a happy guy today.  I hope you all grant me a little lattitude for
this misuse of glowbugs (I looked at lots of tube based boat anchors today,
does that let me off the hook? :-) ).

-- 

Chris F. Broadbent

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

Date: Sat, 3 Aug 1996 21:29:34 -0700 (PDT)
From: [email-masked] (Michael Herr)
To: [email-masked]
Subject: Re: What a great day...
Message-ID: <v01530501ae2ac72597ca@[199.120.150.44]>

>To cut this already too long story short, I am now the owner of two
>certificates of successful completion - one for 5WPM and one for the Novice
>and Tech theory components.  So when I get my license, I'll be a Tech+.
>
>I'm quite a happy guy today.  I hope you all grant me a little lattitude for
>this misuse of glowbugs (I looked at lots of tube based boat anchors today,
>does that let me off the hook? :-) ).
>
>--
>
>Chris F. Broadbent

Chris,
    Congradulations! That is fantastic! Nothing is better than going in
with expectations of knocking off one requirement and ending up with more
than you expected. Now, put together a nice regen receiver, one tube
transmitter on 40 and have a ball!
73
Mike WA6ARA

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

Date: Sun, 4 Aug 1996 14:57:35 -0600 (MDT)
From: [email-masked]
To: [email-masked]
Subject: Ye Olde Valves - Electrical Equivalents?
Message-ID: <[email-masked]>

   Hello,

   I've gotten interested lately, since getting my first AES catalog,
   with trying to closely approximate old 1930-ish self-excited 
   oscillator and regen receivers.

   Through some kind assistance from NA4G, R.D.Keys, I know how to
   substitute a 6SN7 octal for a type#45 4-pin, and a 6C5 or 6J5 octal for
   a UX201-A (01-A) 4-pin.  With some component substitutions, these
   will work fine and are cheaper and easier to get.  A 6J5 substitutes
   nicely for #30's (with more B+) in regens.  (also 6F8G - a dual 6J5)

   However, being the inquisitive anachronist that I am, I wondered if
   there weren't *true* electrical equivalents for the 201-A, 01-A and 45, 
   that existed in the 1930's as 4-pin or 5-pin tubes.  A #27 5-pin, for 
   instance, is a low-mu triode like the UX201-A, 01-A, and seems to be 
   used in similar ways (like regen detectors).  It is also cheaper and 
   more available.  But, is it electrically (if not filamentally :-)) 
   equivalent?

   I have an RCA, circa 1963, receiving tube manual.  These early tubes
   are usually only glossed over, however, and not described enough to
   allow discovering an electrical equivalent.

   I would be very grateful if anyone out there can:

     1) Suggest electrical equivalents for Types #45 (245) , #01-A
        (201-A,301-A), #27 (227,327), #10 (210). 
        (could be 4-pin, 5-pin, or octal substitute)
     
     2) Post or e-mail me technical characteristics of these tubes,
        so I can cross-reference with more modern tube characteristics.

     3) Suggest available reference sources that give detailed technical
        characteristics and/or equivalents of these and other early tubes.

   I surmise, that with the arrival of pentodes, and later, beam power
   pentodes, power triodes (#45, #10) sort of reached a technical 
   extinction in development.  However, the thirties may still have produced 
   some more readilly available tubes that carried their characteristics 
   forward into the indirectly-heated cathode/5-pin/octal age.  Similarly,
   the characteristics of #01-A and #27 may have been carried forward.
   
   Thanks again for any help. 

   ****************************************** 
  ** Shane <[email-masked]> **              
   ******************************************               
        ** Edmonton, Alberta, Canada **                 
         *****************************       

             

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End of GLOWBUGS Digest 253
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