[ARC5] RU/GF vs. RU-Stand-Alone Circuit Differences and Other Info

[Mike Morrow]

Robert wrote:

>Among other differences between (and here I've got to weasel-word and say
>"later" as the earliest GF/RU and RU manuals I have are GF-3/RU-4A and RU-5)
>the later Navy sets and the AAF ones is that all of the Navy radios have
>their filaments wired for 14 volts.  Regardless of what it may say on the
>nameplate.  The 28 volt junction boxes have dropping resistors.  And not
>all of the receivers are interchangable.  The receivers built on the 
>eceiver-only contracts which are at least RU-5, 11/12 and 18/19 are different
>from the ones built on the combined (with GF) contracts.  For example, if
>you plug an RU-17 receiver into an RU-19 Junction Box, it will be dead
>because the AGC amp tube cathode will be floating.  There are other
>differences that I haven't traced out, so I can't currently say whether
>you can do any damage by such mixing.  The Radio Set and the Receiving
>Set dynamotors are also wired differently and are not interchangable.

Here is information from postings that I made in March, 2008, concerning
RU differences (edited to combine or update the original posting):

RU-16/GF-11 (12 vdc) components are identical to RU-17/GF-12 (24 vdc)
components except for the junction box, antenna relay, and dynamotor units.
The RU-17 junction box CW-62018 contains A+ voltage dropping resistors
for filament power going to the 12 vdc receiver CW-46051A and transmitter 
CW-52063A, the antenna relay CW-29076 contains a 24 vdc relay, and the
dynamotor CW-21454A is designed for 24 vdc input.

NOTE: A "24 vdc" blue-tag GF-12 is actually wired for 12 vdc filament power,
and a "24 vdc" blue-tag RU-19 is actually wired for 12 vdc filament power.

The RU-18 (12 vdc) or RU-19 (24 vdc) is designed to go with transmitters
like the GO- and GP-series.  The junction box CW-62007A (12 vdc) or CW-62017
(24 vdc) connects up to two receivers CW-46048D and their control boxes 
CW-23087 to a common dynamotor unit CW-21215A (12 vdc) or CW-21441 (24 vdc).  

RU-19 components are identical to RU-18 components, except for the dynamotor
unit and the junction box, which contains those filament voltage dropping
resistors.  The RU-18 or RU-19 junction box does NOT support interface
with a GF-series transmitter, nor any other transmitter.  I believe that
the transmit/receiver switching took place ONLY in the antenna circuit,
through the relay in the GO or GP transmitter.

The manual for the RU-19 says that the only earlier RU-series receiver with
which it is directly interchangable is the RU-12.  AFAIK, the only circuit
difference between the RU-16/17 (used with GF-11/12) and the RU-18/19 is the
source of negative bias for the AGC stage.

The RU-16/17 derives this in the dynamotor unit, using a tapped resistor to
ground in the negative HV lead from the dynamotor, then sending the bias
voltage through the junction box and on to the receiver.

In contrast, the RU-18/19 runs the negative HV lead from the dynamotor through
the junction box and to the receiver where it returns to ground through a
tapped resistor, where the bias is developed.

The reason for having the bias resistor located in the receiver instead of
the dynamotor unit for the stand-alone receivers is because *two* receivers
may be operated *simultaneously* from the common dynamotor unit in the stand-alone
RU system. If a common bias resistor were used in the dynamotor negative power
lead in the dynamotor unit, as it is in the one-receiver-only RU/GF models, then
the current draw of two receivers through it would greatly affect the bias voltage
generated.  By putting the bias resistor in the receiver, the bias resistors
of the two receivers are in parallel in the negative current path of the
dynamotor.  That maintains the bias generated across the resistors the same
no matter if one or two receivers were being powered from the dynamotor.

Below is a table I've been trying to complete for quite some time.
(The table will look like crap unless your e-mail is displayed as
plain text.)

RU/GF Table:

Transmitter                Receiver                    Contract
Unit  Frequency (KC)       Unit  Frequency (KC)  Volts Date      MFR+
 
GF    6600-7200            GF   224-350, 5400-8100 12            CBY
--    --                   RU                      12            CBY
--    --                   RU-1                    12            CBY
GF    6600-7200            RU-2  224-12500         12            CBY
--    --                   RU-2A 200-400           12  03-31-37  CBY
GF-1  6200-7700            RU-3  224-13575         12  02-10-34  CBY
GF-2                       RU-3A                   12            CBY
--    --                   RU-4                    12            CBY
GF-3  3000-4525, 6000-9050 RU-4A 224-13575         12  06-29-35  CBY
--    --                   RU-5  195-13575         12  05-16-36  CBY
GF-4                       RU-5A                   12            CBY
--    --                   RU-6                    12            CBY
GF-5                       RU-7                    12            CBY
GF-6  2000-4525            RU-8  200-400, 530-5600 12  02-23-38  CBY
GF-7  2000-9050            RU-9  200-400, 530-9050 12  10-31-38  CBY
--    --                   RU-10                   12            CBY
--    --                   RU-11 195-13575         12  11-22-39  CBY
--    --                   RU-12 195-13575         24  11-22-39  CBY
GF-8                       RU-13                   12            CBY
GF-9                       RU-14                   24            CBY
GF-10 3000-9050            RU-15 200-395, 530-9050 12  12-21-39  CBY
GF-11 2000-9050*           RU-16 195-13575         12  04-21-41  CW
GF-12 2000-9050*           RU-17 195-13575         24  04-21-41  CW
--    --                   RU-18 195-13575         12  04-21-41  CW
--    --                   RU-19 195-13575         24  04-21-41  CW
 
+ Manufacturer:  CBY = Aircraft Radio Corp.  CW = Western Electric Co.
* Early issue GF-11/12 frequency range was 3000-4525 and 6000-9050 KC.

The above table shows which RU models were stand alone (no GF in system).

I have information from Michael that the RU-2 was used with the GF, but
also that in the original system, the both the transmitter and the receiver
were nomenclatured as "GF".  Perhaps Michael can verify that the GF
transmitter was used with a GF receiver, but then later was paired with
the RU-2 receiver in place of the original GF receiver.

I suspect, without having the manuals to prove it, that the difference
between the RU-4 and -4A, and the RU-5 and -5A, is the location of the
bias resistor.  (The A models were used with a GF.)

I wonder what transmitter was to be paired with the early RU and RU-1.
Presuming these to date from 1932, that would seem to be before the the
appearance of the GO- and GP-series that served with the later RU-series.

Note that odd RU-2A from 1937.  I have the manual for this.  It's a 
beacon-band only set dated about five years after the RU-2.

Additions or corrections for anything in the above table will be appreciated.

I'd love to see a similar table for the SCR-*-183 abd -283 systems.

Mike / KK5F