[ARC5] Some ARC Type D History and Development

[Mike Morrow]

Mike wrote:

> Has anyone else seen any documentary evidence other than the RU/GF
> manuals?...
> ...That sorta tells me that the use of the RU/GF test meter as a
> permanent fixture in most cockpits wasn't exactly widespread.

I'd agree.  I have some photos on pre-WWII USN two-place aircraft
rear gunner-radioman positions showing the DU and the RU.  I've
never seen any type of meter.  It would have plugged into the RU-*
Receiver Switch Box.  I doubt that, outside some experimentation,
that it was ever present.  It is usually listed in the manual as
an item provided only with some equipments, which would be typical
of items for maintenance and testing rather than in-flight use.

The meter connection is on the RU-3 CBY-46036, and I believe that
is the first.  It was on all subsequent RU-* models, both command
and liaison versions.

The more I've studied what information I have on the A.R.C. Type D
descendants, the more respect I have for the system's design.

Here's my draft of a trace for Type D development,

The USAAC's original SCR-AA-183 (BC-AA-179 receiver, BC-AA-180 transmitter)
had a contract date of 06-25-1932.

The USN's original GF (CBY-46006 receiver, CBY-52004 transmitter)
had a contract date of 11-10-1932.

Thus, it appears that the USAAC was first to adopt ARC Type D gear.  I
suspect that the USAAC's BC-AA-179 and the USN's CBY-46006 receivers
along with the USAAC's BC-AA-180 and the USN's CBY-52004 transmitters
are very similar, perhaps even identical, electrically.

However, only 15 months later, the RU-3/GF-1 (contract 02-10-1934)
CBY-46036 receiver design had reached in all significant aspects
its final stage.  Later in 1934, the RU-3a/GF-2 CBY-52028 transmitter
design likewise finalized future GFs in all significant aspects.

USAAC receivers did not change in any important detail from 1932 to 1935
up through the BC-AD-200 (and actually up to SCR-AS-183 in 1943), with
stages using:
                  RFx4(39x4), Detector/AGC(37), Audio(38)
USN receivers during 1932 to 1934 changed greatly:
  GF   CBY-46006  RFx4(39x4), Detector/AGC(37), Audio(38)
  RU-2 CBY-46012  RFx3(39x3), Detector(36), CW Osc(36), Audio(38)
  RU-3 CBY-46036  RFx3(78x3), AGC(77), Detector(77), CW Osc(half 38233),
                          Audio(half 38233) 
(Anyone with a GF manual, please confirm that the CBY-46006 was so
configured as above.)

During that same time, USAAC's transmitters through the SCR-AD-183
(BC-AD-200) and USN transmitters through GF-1 (CBY-52027) seem to be
almost identical, with both using:
                  MO(10), PA(10), Plate Modulator(45spl), AF Osc(10)
(Anyone with a GF manual, please confirm that the CBY-52004 was so
configured as above.)

For subsequent models after 1934, 

USAAC BC-A*-230 transmitters use a modified AF lineup and RF coil changes:
                  MO(10), PA(10), Plate Modulator/AF Osc(2x45spl)

USN GF-2 CBY-52028 and later transmitters use a radically modified design:
                  MO(89), PA(2x837), Grid Modulator/AF Osc(89)

USAAC BC-A*-230 receivers *continue* to use:
                  RFx4(39x4), Detector/AGC(37), Audio(38)

USN RU-3 CBY-46036 and later receivers use:
                  RFx3(78x3), AGC(77), Detector(77), CW Osc(half 38233),
                          Audio(half 38233)

After 1935, the most significant changes for the USAAC sets seems
to be elimination of the loop antenna connector on the receiver.  The
most significant changes for the USN sets seem to be mods to the
receiver and transmitter to accomodate a two-place interphone system
by adding an extension control box and utilizing the transmitter
AF grid modulator stage as the interphone amp.  The USN also
experimented with the 1938 RU-8/GF-6 and RU-9/GF-7 to get about
20 percent more frequency coverage from a set of receiver coils
by increasing the size of the ganged tuning capacitors (making the
receiver the CBY-46064).  That was not carried on to later models.
Subsequent command receivers returned to the previous CBY-46051 design.
Also, dual-band coil sets were developed for RU command receivers to
provide 540 to 830 kc coverage to process BCB output from the new ZB
homing adapter (which could mount in place of the RU tube cover).

One has to wonder why, somewhere around 1935, the USAAC and ARC didn't
consolidate all designs and settle on the more capable USN version that
existed by late 1934.  I doubt that there would have been gross cost
differences, especially once everything was being made the same and parts
supply was simplified.

Regardless, the engineering of these early-1930s radio sets seems to be
very respectable.  They certainly deserve better appreciation than what
hams gave after WWII.  The Type D descendants were always treated with
great disdain, but someday I intend to have a RU-16/GF-11 with ZB-3 (I have
most of what I need now), along with my SCR-AS-183.  Those final Type D
command sets represent the high point of the A.R.C. Type D story, IMHO.

(Anyone got a manual for the SCR-AA-183?)

Mike / KK5F