[Milsurplus] AN/URT-18 transmitter??

[John Vendely]

Thanks, Jim, and also thank you to Dave Ross and Jim Young for your 
intelligent and constructive comments on the AN/GRR-13.  I dug out the 
equipment today,and took a close look at it for the first time in about 
20 years.  The receiver was built in 1962 under an Air Force contract, 
and  is of  typical KWT-6 style fixed-station  construction, and 
containing very lightly constructed modules typical of Collins airborne 
sets of the time.  It has every appearance of being an airborne set 
modified and repackaged for ground station use.

The set was designed around common miniature tubes and a smattering of 
germanium transistors, and features local or remote autotuning.

Its major components are:

Control, Receiver C-4438/GR, frequency selector unit with one set of 
decade switches for tuning in 1 kc steps, plus telephone-style toggle 
switches and indicator lamps for USB/LSB/AM mode selection.  Also has 
indicator lamps for oven temp, and a "Ready" lamp, apparently indicating 
tune cycle completion.

Radio Frequency Detector Group, OA-4376/GRR-13, a motor-driven, 
slug-tuned RF section, plus IF and demodulation section of the receiver.
Also present is a very similar unit, Amplifier-Modulator Group, 
OA-4515/GRT-12, containing the sideband generation, IF, and RF stages of 
a companion transmitter.  Most of the modules are apparently shared by 
both receiver and transmitter exciter.

The quaintly named Oscillating Group, OA-4374/GR, which contains 
ovenized  frequency standard with 1 Mc and 100 kc outputs, mechanically 
coarse-tuned/phaselocked master oscillator assembly, analog frequency 
divider and  frequency multiplier modules, and a motor-driven slug-tuned 
tuned amplifier strip, perhaps the harmonic selector for a harmonic 
spectrum generator.

Control-Power Supply, C-4439/GR, a 28V DC regulated supply, plus 
controls for selecting local or remote control.

There is also a 400 cps power supply, a  junction box, blower/air plenum 
assembly, and a quantity of interconnect cables with Amphenol "Blue 
Ribbon" type connectors.

I have a few duplicates of the frequency selector and power supplies, 
but unfortunately, only one each of the OA-4374 and OA-4376.

I'll send you and Dave some pix of the equipment. Despite the apparent 
dearth of documentation, I don't think the set is particularly rare, 
though it may have been better known by other nomenclature.  I recall 
seeing this equipment as surplus fairly often in the late 70s, early 
80s.  Doubtless you'll recognize it when you see it...

tnx, 73,

John K9WT

On 11/13/2010 3:04 PM, Jim Whartenby wrote:
> Sure John, pictures are welcome!
> I have some manuals which I would be happy to copy if that will help.  Also have
> gained some experience working on two URC-32s and one 310F-6 so I know some of
> the pitfalls.  Reworking the power supply and blower motor are first order
> issues, followed by getting the SMO back in sync.  The Interpolation Oscillator
> is the problem there.
>   
> You say that the frequency selector is different?  I guess that there is no
> mechanical odometer type frequency readout?  If the frequency selector is rotary
> switches then this radio could be like the 310F-1 which is an auto-tuned radio. 
> Look for two servo amplifier modules, one 5 watt, one 2 watt, easily identified
> since there are two small pots on the module front.
>
> I can take a picture of the 310F-1 to give you an idea what it looks like.  All
> is mounted on the rack except for the motor-generator.  I will have to make a
> one inch spacer for each side of the rack so that the back of the M/G assembly
> doesn't hit the plenum.
> Jim
>
>
> ----- Original Message ----
> From: John Vendely<jvendely at cfl.rr.com>
> To: milsurplus at mailman.qth.net
> Sent: Sat, November 13, 2010 11:24:22 AM
> Subject: Re: [Milsurplus] AN/URT-18 transmitter??
>
> Hi Jim,
>
> Thanks for the reply.  Yes, the AN/GRR-13 has exactly the same style of
> construction as all the KWT-6 variants--the familiar light gauge metal
> covers with toggle snaps, with the entire set mounted in an open relay
> rack.  The individual chassis are designed to unlatch and swing out for
> servicing.  The frequency selector unit looks a bit different from the
> 310F-6, as does the number and arrangement of subassemblies.  I always
> assumed it was merely a military nomenclatured version of a standard
> product, but I don't see anything in the Collins catalogs of the time
> which looks identical.  I really have never spent much time analyzing
> it, though I'm sure it must be just another variation on the KWT-6
> theme.  Manuals for the other variants might well serve as a guide. 
> This discussion has certainly piqued my interest, and I could furnish
> some pix in case you're curious about it...
>
> 73,
>
> John K9WT
> ______________________________________________________________
> Milsurplus mailing list
> Home: http://mailman.qth.net/mailman/listinfo/milsurplus
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Milsurplus at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>