[ARC5] Wanna Build GF/RU?

[Mike Morrow]

Dave wrote:

> If you are serious about building a GF/RU, there is 
> a nice, clean and very reasonable one on the Bay right
> now.
>
>   https://www.ebay.com/itm/372629560692

Dave, I know we both admire the RU-*/GF-* command set design by A.R.C. for the US Navy in the mid-1930s.  It was a world-class design for a light-weight system that with its later dual-band receiver coils for use with the ZB-* VHF homing adapter provided a lot of capability that served USN carrier aviation rather well early in WWII.

Unfortunately, that auction is ONLY for the junction box CW-62007A for 12 vdc LIAISON receiving system RU-18.  It is NOT one bit usable with ANY RU/GF COMMAND set, even a ham-kludged conglomeration.

Some RU-16/GF-11 Command Set and RU-18 Liaison Set components (receiver, junction box, dynamotor, control boxes) **appear** similar, but all except one control box have very significant electrical differences which make them completely non-interchangeable between liaison set and command set installations.  Just compare in detail the auction's CW-62007A RU-18 liaison set junction box against the contemporary CW-62008A RU-16/GF-11 command set junction box.

CW-62007A RU-18 LIAISON Set Junction Box
a.  Has connections for
-> CW-46048D RU-18 Receiver A
-> CW-46048D RU-18 Receiver B
-> CW-21215A Dynamotor-Filter (12 vdc to 345 vdc)
-> CW-23087 Receiver A control box
-> CW-23087 Receiver B control box
-> 12 vdc Power.
b.  Connects directly to 12 vdc power source.
c.  Contains a power-on relay.
d.  Has NO transmit-receive circuit switching.  That takes place only in the associated GO-* or GP-* transmitter's antenna relay.
e.  Directs 345 vdc RC-filtered HV to Detector and AF stages, plus LC-filtered HV to the other stages of receiver A.  Directs LC-filtered HV to all stages of receiver B.  This reduces AF cross-talk between receivers in two-receiver installations.
f.  Connector to receiver is 10-pin.

CW-62008A COMMAND Set Junction Box
a.  Has connections for
-> CW-46051A RU-16 Receiver
-> CW-52063A GF-11 Transmitter
-> CW-21109A Dynamotor-Filter  (12 vdc to 425 vdc)
-> CW-23096A Receiver control box
-> CW-23097 Transmitter control box
-> CW-23098 Extension control box
-> CW-23049 Antenna relay.
b.  Connects to 12 vdc power through the Dynamotor-Filter.
c.  Contains no power-on relay.  That is in the Dynamotor-Filter.
d.  Has a transmit-receive circuit switching relay that when energized switches HV from receiver to transmitter, plus shorts out the AGC bias resistor in the Dynamotor-Filter to eliminate its voltage drop in the 425 vdc HV supply to transmitter.
e.  All HV supplies are LC-filtered.
f.  Connector to receiver is 11-pin.

Thus, junction box CW-62007A is wildly incompatible with any RU/GF command set installation.

A complete two-receiver RU-18 would be a very appropriate mate to a GO-9 or GP-7 liaison transmitter, but very very inappropriate for a GF-11 transmitter.

BOTTOM LINE:  Nobody should consider the junction box in the auction if he seeks to assemble a RU-16/GF-11 or any other RU/GF set.

Mike / KK5F