[Milsurplus] BC-9 Loop Test: Scratching My Head.

[David Stinson]

----- Original Message ----- 
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>

> Is it possible that this +/- 12 kc difference between the TX 
> and RX frequencies was well
> known at the time, and was used effectively for their comms? 
> "I'll transmit on such and such
> a frequency, and will listen on such and such a frequency". ?

Not possible.  TX/RX freq is set by a common
control. And this is not a superregen AM rig on
VHF, where one could communicate to a station
200 KC off freq.  On RX, it is an HF regen detector.
The received signal must be close enough so that the beat
note will be within the range of human hearing
and the audio response of the rig/headphones;
5 KC or so.  A beat-note of 12 KC would not
be useable.

This simply cannot be "normal."  The set was
in service for over a decade.  The U.S. Army
Signal Corps of 1918-1931 had a very small
budget and could not afford to waste it on
several contracts for a radio that did not work.

I understand what Neil is saying, but the diagram
I've posted matches the wiring in the set.
Nick Broline has suggested an issue with the
grid bias that I will be investigating.

One big problem-
We have only fragments of a manual from
earlier verisions of the set. There was an original design
from 1918, which was "improved" to BC-9, which was
then improved again to BC-9A and again to BC-9B,
which is what I have. The version in the manual is,
IIRC, the "no sub letter" and is different from the -A
and the -B. The -A diagram is:
https://goo.gl/photos/DycqNJdQ24aC2afF7
I don't know what is different in the -B, but the diagram
above is what came with the -B set and seems to match
what I'm seeing.

Must get back to work for now.
Thank you thank you for your ideas and discussion.
We WILL solve it.
73 Dave AB5S