[Milsurplus] RE: [ARC5] RU/GF documentation

[Mike Morrow]

>After REALLY looking at the labels, the set is not RU-16/GF-11 but RU-19 and
>GF-12. Does that make any difference?

Hi Meir,

As Robert mentioned, there are differences between the RU-17 normally used with the GF-12 and the RU-19 that you have.  I thought I'd throw in some specific details.

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.  

NB:  Your "24 vdc" blue-tag GF-12 is actually wired for 12 vdc filament power.

The RU-18 (12 vdc) or RU-19 (24 vdc) are 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 only transmit/receiver switching took place in the antenna circuit, through the relay in the GO or GP transmitter.

NB:  Your "24 vdc" RU-19 is actually wired for 12 vdc filament power.

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 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.  Why this different configuration to do the exact same thing was used, I don't know. 

The easiest way to adapt a RU-19 to work with a GF-12 will depend on which dynamotor unit you have.  The RU-19 junction box will be essentially unusable.  It would be easiest to find an RU-17/GF-12 junction box.  You'd have to be careful connecting the RU-19 dynamotor to it, since there are a few significant differences in the RU-17 dynamotor unit.  You'll need to add a RU-17/GF-12 antenna relay.

The RU-16/GF-11 is one of my favorite sets.  Though the manual is dated 21 April 1941, the flavor is definitely "mid-1930s" technology.  The finest examples will bear the same serial numbers on ALL units.

Mike / KK5F