[ARC5] Command Set Receiver Audio Transformers REV-1

[Bill Blodgett]

Thank you Bill for sharing your research !

73,
Bill
W5WHB
++++++++++++++++
Bill Blodgett
Arlington, Texas

> On Mar 26, 2026, at 12:29 PM, Bill Cotter via ARC5 <arc5 at mailman.qth.net> wrote:
> 
> Hello all,
> 
> Attached is the first revision of Command Set Receiver Audio Transformers paper I compiled while trying to figure the differences in about 20 of these old receivers. Included are actual measurements to confirm what has been found in the literature.
> 
> Addition, corrections, and criticisms welcome.
> 
> 73 Bill N4LG
> 
> ==================================================================
> 
> I have been in the process of repairing and upgrading several old command set receivers with the goal of getting a stack of these functioning on 160M, 80M and 40M. And, eventually getting the matching transmitters back into working condition.
> 
> One thing that has bothered me over the past month are all the differences in audio output transformers that were used in these radios. My goal was to get them all set to work with 600Z output.
> 
> After digging through a lot of tech manuals, conversion manuals and magazine articles, I have figured out what I didn't understand about the types and choices of the output transformer used in all the common sets. When I go through the process of researching everything about a topic, I compile my notes for when I forget down the road, hi!
> 
> Attached are my notes on the BC-4XX and ARC/R-2X receiver audio transformer options. Hopefully, these notes can save someone else from a lot of head scratching.
> 
> Any comments, corrections, contributions, etc are welcome.
> 
> 73 Bill N4LG
> 
> 
> <Command Set Audio Transformers N4LG 20260326.pdf>
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