That's some really excellent work Bill!  Well done!
Thank you...
Tim
N6C

On Thu, Mar 26, 2026 at 10:29 AM Bill Cotter via ARC5 <arc5@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


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