[ARC5] More Data on GF and RU-2

[David Stinson]

I did some digging and have some "good stuff" to add.
I have the manual for the original GF set here, thanks to 
Phil ("he da man!").

First- the original receiver in the "GF" set- CBY-46006,
Contract NOs-29086 November 10, 1932,
did indeed have AGC (and they called it that).  
They derived it from the plate/grid of the Detector tube, 
a CBY-38037 triode (type 37) with the plate and grid 
connected together to function as a diode.  
The rectified RF was feed from the 37 plate/grid
before the audio stage input coupling cap, 
back to the first two RF stages.  
It did not have a CW osc. Freq range of the receiver 
was 224-350 KC and 5400-8100 KC in two coil ranges.
Transmitter freq was 6200-7700 using one coil "set,"
which, unlike the later Tx coils was divided between
the osc./interstage shielded coil and the PA/Antenna coil.
Only the PA/Ant coil was normally removeable.

The RU-2 receiver, CBY-46012, purchased on the 
same contract and included in the same manual, 
is a very different cat.  It does not have AGC but
does have a CW osc.  It covers 224-12500 KC 
in ten coil sets.  The inference is obvious: 
this receiver was intended for Liaison service.

Now here's where "the plot thick-nen-nez" with
the discovery of a receiver manual I'd forgotten I had:
                  RU-2A CBY-46012A
Which is again, a different cat from either the 
"GF" CBY-46006 or "RU-2" CBY-46012.
It covers only one band with one coil: 200-400 KC.
And here it gets "hinky," because the contract is
N156s6990, March 1 1935- better than a year *after*
the Feb. 1934 date of RU-3.  In fact, the RU-2A manual 
states the RU-3 coils cannot be used with RU-2A.
There circuits of RU-2 and RU-2A are close, but not
quite the same.  The RU-2 has a Hi-Z audio out, while 
the RU-2A is Low-Z only.  The RU-2A audio output 
also differs in that there are a coil and resistor in series
connected between the "cold" side of the audio output
transformer primary and the output's plate.  This coil
is called-out in the parts list as an "output booster choke"
but it's function is not explained in the circuit description.
The only use I can see is to provide another B+ path to
the tube that bypasses the audio output tranny's primary
and the audio low-pass filter in the audio output plate lead.
The RU-2 does not include these parts.

Given the documented practice in the Navy of issuing
the leader of flights- especially those for training 
and ferrying- a full Command Set radio and
the others a beacon receiver only, I think it likely this 
was the intent of the RU-2A.  It would have filled the 
gap left for such a set in the line-up of GF Command,
RU-2 Liaison, and the wing-man "beacon" set.
 
So first was "RU," the prototype derived from "Model D"
and tested by the fleet in 1931.
Next came the "GF/GF" receiver, CBY-46006.
Then the RU-2, CBY-46012, a Liaison set.
Then the RU-3, Command and Liaison versions.
Then the RU-2A, CBY-46012A beacon/homing set.

This leaves us with a mystery... what happened to RU-1?
Someone has the manual... someone.
And another- what's up with that contract number,
N156s6990?  I thought numbers like that only 
came long late-or-post-war?

And if you think this is wicked, wait until I write you 
about The Great SCR-AF-183 Mystery.
Need Sleep for now.  Tomorrow.  
(Clue- A.R.C. didn't do it).

73 Dave AB5S