[Milsurplus] 400 MHz cavity

[Brenda Gentry]

  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 
> <frledda at att.net> wrote:
>
>
> More info below:
>
> https://www.navy-radio.com/xmtrs/src20.htm
>
> *From:*milsurplus-bounces at mailman.qth.net 
> <milsurplus-bounces at mailman.qth.net> *On Behalf Of *frledda at att.net
> *Sent:* Sunday, March 30, 2025 4:54 PM
> *To:* 'Gary Hitchner' <talgarth at comcast.net>; 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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