Comments on Central Electronics 20A

Bob Maser w6tr at MINDSPRING.COM
Sat Jun 23 00:39:36 EDT 2001

Welcome "no code".
-----Original Message-----
From: Glen E. Zook <gzook at HOME.COM>
Date: Friday, June 22, 2001 9:01 PM
Subject: Comments on Central Electronics 20A

>I am new to this particular reflector but feel I must reply to one of
>today's messages.I do not like the practice of "putting down" other
>amateurs.  I have always believed that amateurs, in general, are a
>trusting, helpful bunch of guys and gals (men and women for the
>politically correct among us). I am against the practice of amateurs
>"taking advantage" of one another,I am against making "snide" remarks
>either to someone.  I am definitelyagainst stealing from another amateur
>(or anyone for that matter!),against running up of fictious repair bills
>for the purpose of obtaining equipment because the amateur who owns the
>equipment can't pay the bill, and similar actions.  Frankly, I have seen
>it all!
>I am definitely of the "old school" where amateurs help each other. When
>the following E-Mail was brought to my attention, I was disturbed.
>Date: Fri, 22 Jun 2001 16:06:35 -0500  From: "k5ceg at"
>i  see a post a couple of days ago for a modulation transformer for a
>central electronics 20 a, i am wondering if i missed something.maybe
>this phasing type exciter had such a thing??? i have 6 of them and cant
>seem to locate 3 modulations transformers in them.or maybe this was a
>mistake by someone that held a conditional class license or something.3
>modulations transformers in a 20a would weigh about 50 lbs or i
>missed informed or what??? or maybe one needs to go back to
>The Central Electronics Model 20A is one of the first SSB transmitters
>produced commercially in the United States.  Using a pair of 6AG7 tubes
>in the final amplifier, it produces a maximum output of 20 watts PEP.
>This is a complete transmitter, including power supply, utilizing
>"phase" type generation of the SSB signal instead of the now, more
>common, "filter" generation.  However, the 20A uses either
>crystalcontrol, or, a modified ARC-5 command transmitter VFO. The
>Hallicrafters HT-37 transmitter and the Heath SB-10 SSB adapter are
>common examples of "phase" generation transmitting equipment
>The approximate weight of the entire unit is 40 pounds. Since this
>transmitter does not utilitze the "normal" plate modulation scheme,
>there is no plate modulation transformer.  However, if there were a
>plate modulation transformer, the weight of it would be in the
>neighborhood of a pound, or two, because it would only have to provide a
>maximum of 10 watts of audio to fully modulate 20 watts This is opposed
>to the "over 50 pounds" claimed by K5CEG. When used on AM the signal is
>generated by inserting the carrier (unbalancing the balanced
>modulator) and was amplified by the pair of 6AG7 tubes which are in a
>linear amplifier configuration.
>The schematic refers to the two transformers after the 12AT7 "A F
>Modulator" tube (their designation) as "Mod Trans" (short for modulation
>transformers- part number 27A0-79-3).  From the diagrams in the manual,
>appear to be cylindrical in nature, probably about 1.5 inches in
>diameter.  I would doubt that they weigh more than about 0.5 pounds,
>probably sless.  The SB-10 adapter has two similar transformers in the
>generation circuitry (also called "modulation transformers" by Heath -
>p/n 51-38). As in the Central Electronics 20A, those in the Heath SSB
>adapter are also very small, about 2 inches square by about 2.5 inches
>high.  These weigh, in my estimation, about 3 or 4 ounces each, not over
>50 pounds combined weight!
>The 20A and SB-10 use a 12AT7 as the audio modulator. The 20A manual
>does not give the impedances of the modulation transformers, the Heath
>manual does.  The transformers are a 1:1 turns ratio with impedance 20K
>ohms.  I would think the 20A would be similar.
>Therefore, calling the transformers labeled as TR-2 and TR-3 "modulation
>transformers" is completely correct. This is the nomenclature used by
>Central Electronics and Heath when describing them.
>As a direct result of this information, I believe that K5CEG owes some
>heartfelt apologies to those persons he has tried to insult with his
>comments about needing to go back to school and about their previous
>class of license.  Unless, of course, he is admitting that he has to go
>back to school and learn how to read the nomenclature on various
>manufacturer's schematics, to learn how to properly capitalize his
>typing (i.e. "I", not "i"), spelling (uses "excellant" on his web site
>instead of the correct spelling of "excellent" when describing equipment
>condition on, proper use of the plural noun (used
>"modulations" instead of "modulation"), improper verbage (used "missed
>informed" instead of "misinformed"), and so forth .  If that is the
>case, I am sure that the Paris, Texas, school system has adult education
>classes that he can attend for the purpose of expanding his knowledge.
>If he did not mean this action for himself, then I again appeal to him
>to offer his apologies.
>Because I am new to the reflector, I was asked by some "older" members
>to take a look at K5CEG's comments and make my own comments on them.  I
>have only met K5CEG once, and I am fairly sure that he does not want me
>to reveal the reason and the results of that particular meeting.
>Again, I am from the "old school" where amateur radio operators help
>each other, not try to hurt each other.  So, let's do our best to try
>and help each other rather than "tearing each other down".  How about
>Glen, K9STH

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