[Milsurplus] More Data on GF and RU-2

[Mike Morrow]

Dave wrote:

>First- the original receiver in the "GF" set- CBY-46006, Contract
>NOs-29086 November 10, 1932, did indeed have AGC...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.

That seems to tie firmly together the GF CBY-46006 receiver to the
SCR-A*-183/283 receivers.  The CBY-46006 and ALL of the SCR receivers
have identical stages (four RF 39/44, detector 37, AF 38), without
CW oscillator.

I don't know what the electrical differences are between the BC-AA-179,
BC-AD-219, BC-AB-199, and BC-AD-199, (SCR-AA, AB, AC, and AD-183) but
these used antenna posts for the loop connection.   The BC-AE-229
and later sets (until the loop function was eliminated) used a loop
cable connector.  

The SCR-AA-183/BC-AA-179 contract was 06-25-1934, and the GF/CBY-46006
contract was 11-10-1932.  I guess the honor of being the "first" goes to
the USAAC and not the USN.  But the USAAC did little development of the
system during the entire history of their sets...the -AS- set made in 1943
differs very little from the -AA- set made in 1932.  The USN very early
made significant improvements of both the transmitter and receivers.  The
USN sets of late 1934 differed markedly from those of 1932.  However,
there are only minor differences in USN sets appearing after late 1934.
  
>The RU-2 receiver, CBY-46012, purchased on the same contract and included
>in the same manual,...

Was the manual itself dated 11-10-1932, or was it a little later AFTER
the RU-2 CBY-46012 started replacing the original GF CBY-46006 as companion
to the GF CBY-52004 transmitter?  An excerpt I found from a GF/GF set manual
shows only the original GF CBY-46006 receiver.

>...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.

The RU-2, RU-3, and RU-4 were intended as liaison receivers, but the
RU-2 served command function with the GF, the RU-3 with the GF-1, and
the RU-3a with the GF-2.  Thus began a short-lived convention of assigning
"a" to the command set version.  The RU-4 was liaison but the RU-4a served
command function with GF-3...and the RU-5 was liaison but the RU-5a served
command function with GF-4.

It seems only the RU-2 and RU-3 served either command or liaison function.
Mike's document at http://aafradio.org/docs/1935-Navy-Radio-Gear.pdf notes
"The fighter planes on carriers are provided with model GF transmitters and
model RU-2 receivers."  There are other statements elsewhere that firmly 
associate the RU-2 CBY-46012 with the GF CBY-52004, in place of the GF
CBY-46006.

In another portion of the same document that discusses the RU-3 and -4, it
states that "The actual coil sets provided vary with the service for which
the receivers are intended.  Generally the ranges 224 to 350 kc, 3,000 to
4,525 kc, and 5,200 to 7,700 kc are provided for receivers used with the
GF series transmitters..."  What coil sets were provided for the RU-2
according to your manual for the GF/GF and RU-2/GF?

>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.

That's also a lot earlier than the 1937 date for the RU-2a given in SHIPS 242A
(January 1945).  I have a manual for the RU-2a on contract "NOs 53913, dated
March 31, 1937".  By that time, the RU-6 was out.

>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.

The description of the RU-2 versus RU-2a at http://aafradio.org/docs/RU-2A.pdf
is a little misleading with its statement "The RU-2A receiver is designed for
beacon beacon installation and electrically is identical to the RU-2 receiver."
As you say...it's close.  The AF output impedance difference would at least
have been notable in that old document.

I believe the choice of the RU-2a for beacon service was entirely logical,
based on the need for a receiver that has no AGC and, in the case of the RU-2a,
can not even by error be put in AGC mode.  AGC was something to be avoided when
homing aurally on those directional Adcock A-N beacons of the era.  All other
RU models had some form of AGC that could be selected. 

>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.

It also uses the same CBY-21015 dynamotor, CBY-23011 junction box, and other
components of the GF/GF and RU-2/GF sets, FWIW.

>So first was "RU," the prototype derived from "Model D" and tested by the
>fleet in 1931.

SHIPS 242A information is odd.  It states a 1930 date for the RU and claims
a 250 to 1800 kc frequency coverage.  Typos??

>Next came the "GF/GF" receiver, CBY-46006.

Could the CBY-46006 also have been assigned to the RU-1 in addition to
the GF, the same way that the CBY-46104/5/6 were assigned to both the
RAV and the ARA?
 
>Then the RU-2, CBY-46012, a Liaison set.

And also the first RU-series command set, used with the GF CBY-52004
(1933).

Questions remain:
1.  When and what prompted replacement of the GF CBY-46006 receiver with
    the RU-2 CBY-46012?
2.  Were new installations made of the RU-2/GF, or was it always a backfit
    of the RU-2 to existing GF/GF installations?

>Then the RU-3, Command and Liaison versions.

In 1934.

>Then the RU-2A, CBY-46012A beacon/homing set.

Which had several years service, judging from the 1937 order.

>This leaves us with a mystery... what happened to RU-1?

SHIPS 242A says RU-1 was 1931, 250 to 14000 kc frequency coverage.  It may
be also be a CBY-46006, but if also intended for liaison function, the lack
of a CW oscillator would be very limiting.

>...wait until I write you about The Great SCR-AF-183 Mystery...
>(Clue- A.R.C. didn't do it).

The table I posted yesterday has another error where it indicates the
SCR-AF-183 was made by A.R.C.  Mike Hanz's page on the SCR-AE-183 mentions
that the 1935 SCR-AF-183 was made by WE Co.  Unexpected in itself.

I love these discussions of radio sets that are approaching 80 years old!
Thanks, Dave, for providing some information that ties stuff together.

Mike / KK5F