[Milsurplus] 400 MHz cavity

Sun Mar 30 22:04:15 EDT 2025

Here is a link to the whole manual.

https://www.navy-radio.com/manuals/src20-21-0967-438-9010-7301.pdf
src20-21-0967-438-9010-7301
PDF Document · 63.8 MB

I actually have a rough hard to read copy of the URC-9B manual (FM capable but never went into production and was replaced by the WSC-3)

Daniel Jones (K6YIC)
DJones at k6yic.com
http://K6YIC.com
HH Phone #11973
SKCC#28598
CCA# AC20-13565

> On Mar 30, 2025, at 18:07, Francesco Ledda via Milsurplus <milsurplus at mailman.qth.net> wrote:
> 
> I believe to be a linear. If you are interested, I have its schematic.
> 
> Best, Francesco K5URG
> 
> Sent from my iPad
> 
>> On Mar 30, 2025, at 19:24, Brenda Gentry via Milsurplus <milsurplus at mailman.qth.net> wrote:
>> 
>> 
>>  I had plenty experience with GRA-53 transceivers. They are very proficient in cremating themselves. Unauthorized fans on the outside of the cabinet helped a little. The worst were ARC-27s used in GCA trailers. They cooked themselves so badly everything inside was dark brown. Is the SRC-20 amplifier a linear or does it have a modulator driven by the exciter?  Near the end of my term in the Air Force, we got some VHF transmitters that used a 10 watt AM exciter to drive a one tube linear to make 40 watts. Linear amps and AM are so inefficient. GRC-27s were huge and heavy, but were plate modulated and put out a good signal.
>> 
>>    B. Gentry, KA2IVY
>> 
>> On 3/30/25 7:00 PM, Jim Whartenby via Milsurplus wrote:
>>> I would say that the URC-9 is similar to the VRC-24 in that both are UHF Transceivers and that the modules look to be similar but the modules are not interchangeable, specifically the PA module.  Now the TRC-68, GRA-53, GRA-54 and the VRC-24 all seem to have the same modules, but I never worked an the VRC-24 which is a 28 volt DC powered unit.  
>>> 
>>> When I was in the Air Force, stationed in the Philippines, I worked on the TRCs and GRAs.  They ran so hot that one had to wait half an hour for the R/T unit to cool off before you could carry it back to the shop.  Fun times! 
>>> 
>>> The URC-9 was Navy equipment and they never seem to buy "off the shelf", they always have to change things!  <grin>  The URC-32 vs the KWT-6 Type 8 is another example.
>>> Jim
>>> Logic: Method used to arrive at the wrong conclusion, with confidence.  Murphy
>>> 
>>> 
>>> On Sunday, March 30, 2025 at 04:56:21 PM CDT, frledda at att.net <mailto:frledda at att.net> <frledda at att.net> <mailto:frledda at att.net> wrote:
>>> 
>>> 
>>> More info below:
>>> 
>>> https://www.navy-radio.com/xmtrs/src20.htm
>>> 
>>>  
>>>  
>>> From: milsurplus-bounces at mailman.qth.net <mailto:milsurplus-bounces at mailman.qth.net> <milsurplus-bounces at mailman.qth.net> <mailto:milsurplus-bounces at mailman.qth.net> On Behalf Of frledda at att.net <mailto:frledda at att.net>
>>> Sent: Sunday, March 30, 2025 4:54 PM
>>> To: 'Gary Hitchner' <talgarth at comcast.net> <mailto:talgarth at comcast.net>; Milsurplus at mailman.qth.net <mailto:Milsurplus at mailman.qth.net>
>>> Subject: Re: [Milsurplus] 400 MHz cavity
>>>  
>>> Gary,
>>> 
>>> The cavity amp you have was part of the Collins AN/SRC-20.  The transceiver/exciter is the AN/URC-9, also known as AN/VRC-24.
>>> 
>>> It is a nice amp that can be easily tuned to 432 MHz.
>>> 
>>> Best, Francesco K5URG
>>> 
>>> 
>>> 
>>>  
>>> From: milsurplus-bounces at mailman.qth.net <mailto:milsurplus-bounces at mailman.qth.net> <milsurplus-bounces at mailman.qth.net <mailto:milsurplus-bounces at mailman.qth.net>> On Behalf Of Gary Hitchner via Milsurplus
>>> Sent: Sunday, March 30, 2025 2:50 PM
>>> To: Milsurplus at mailman.qth.net <mailto:Milsurplus at mailman.qth.net>
>>> Subject: [Milsurplus] 400 MHz cavity
>>>  
>>> List,
>>> 
>>> I have two of these which are going to scrap unless someone tells me there is a reason not to.  (Or picks them up local).  Large and heavy.
>>> 
>>> These are a 225- 400 MHz cavity that used 2- 4CX250k’s in parallel, evidently  conversion to 432 was possible, but a project.  Fair Radio might have had them in stock for a while, or maybe Skycraft, not sure.
>>> 
>>> Often wanted to see the entire assembly these were in, must be something to see………….
>>> 
>>> Gary
>>> 
>>> WA2OMY
>>> 
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