[Milsurplus] AN/WRA-3 synthesized CW exciter

[John Vendely]

Hey Nick,

I have a WRT-2, and a supplement in its manual makes reference to its 
use with "Transmitter Group WRA-3" as a substitute exciter. The 
supplement only describes interconnection of the WRA-3 to the WRT-2 via 
"Transmitter Transfer Control C-6562/WRA-3", a simple switch box.  The 
transfer box disconnects all remote keylines to the WRT-2, disconnects 
its internal exciter system, and routes the WRA-3 RF output to the grid 
circuit of the WRT-2 PA 2nd driver stage.  WRT-2 transmit keyline is 
then solely from the WRA-3.

The exact purpose of this setup is not described, only the 
interconnection arrangements, but the interconnection is clearly for the 
purpose of using the WRA-3 as an RF drive source for the WRT-2 power 
amp.  Since synthesized exciters of the WRT-2 and URC-32 generation were 
a bit cranky and unreliable, the need for a backup exciter is 
understandable.  However, I also have a couple of the Manson 
Laboratories O-1115 synthesizers, and can attest that these aren't any 
more reliable than the WRT-2's synthesizer. Still, some redundancy would 
certainly make sense, and if the redundant unit is of a completely 
different design, so much the better.  I suppose the WRA-3 would be 
useful as a high-accuracy HF signal source for testing and general 
purpose use, as well as a low power backup transmitter in its own right.

The WRT-2 manual supplement makes no mention of the WRA-3 emission mode, 
but if it was considered a backup exciter, it would surely make more 
sense if it had SSB, or at least FSK capability.  Your unit has the 
synthesizer, power amp and its power supply, but what is the third 
missing unit?  Perhaps it's some form of modulator? It's awfully large 
to be simply a hand key interface, unless perhaps it's a programmable 
machine keyer.  The WRT-2 does have a separate machine CW keyer input.

I'm curious to know what you find out...

73,

John K9WT



On 6/17/2013 1:57 PM, Nick England wrote:
> Hi gang -
>
> http://www.navy-radio.com/xmtrs/wra3/wra3-11.JPG
>
> Does anyone know what this gadget was used for? NTDS maybe?
>
> A 600 lb. synthesized VFO 0.5w 2-30 mc
> It is an exciter for URC-32 and WRT-2 according to spec sheets and
> field changes.
> What for? No mention of FSK, just CW.
>
> Could also be used in "high power" mode with 15 watts out.
> A pretty hefty. QRP rig...
>
> CY-3022/WRA-3 cabinet
> O-1115/URC synthesizer
> AM-2819/WRA-3 amplifier
> PP-2796/URA-3 power supply
>
> Also shown as part of a prototype AN/WRT-4 (XN-2) transmitter
> Submarine use with 1 kw water-cooled amp. Again, nothing shown in the
> spec sheet but a hand key for CW.
> Weird.
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