[Milsurplus] Collins Modulators For Sale

[John Vendely]

The MD-129 is part of AN/GRC-27, which was a synthesized 220-400 Mc (100 
kc steps) fixed station set based upon the design of the ARC-27.  It 
provided supply voltages as well as modulation power to the associated 
transmitter. Transmitter output power is 100W, so these modulators do 
not develop "a cool 500 watts", more like 50 watts.  Most amateurs 
greatly overestimate the output power of military equipment, based on 
its size in relation to the amateur equipment they're familiar with, and 
the seller is apparently similarly influenced.  Input power consumption 
is certainly at least "a cool 500 watts", however, with the transmitter 
at 100% modulation.

About 30 years ago I had a complete GRC-27, and kinda wish I still did.  
I got it for essentially nothing, and ended up giving it away.  They're 
huge, impressive, and beautifully built.  They seem to work just fine 
down into the 220 Mc amateur band, and I used it there upon occasion.  
The GRC-27 was a beautiful set, so I hope it's possible to save the 
modulators, and possibly restore a system...


73,

John K9WT

On 10/13/2013 11:43 PM, COURYHOUSE at aol.com wrote:
> I think these are  for grt 3 transmitters??
> if we can save them and get them to Arizona in the back of a truck or   car
> that is headed  here anyway    we would provide  a  home  for them
>   
>   
> the weight of these   is  why I ended up  after a car  accident   working
> at the mars station...   too  heavy for a crip  to lift!
>   
>   
> Ed Sharpe Archivist  for SMECC  _www.smecc.org_ (http://www.smecc.org)
>   
>   
>   
> In a message dated 10/13/2013 8:26:37 P.M. US Mountain Standard Time,
> iron.horses at verizon.net writes:
>
> Dear  Military Surplus Newsletter
>
>
> Could you please include the following  text in your next issue.
>
> I have these wonderful boat anchors and would  like to find a good home
> for them and some remuneration as well if  possible.
>
> I place the text below.
>
>
>
>
> I HAVE FOR SALE  TWO SURPLUS COLLINS-MADE MD-129s MODULATORS/POWER SUPPLIES.
>
> THEY  HANDLED LARGE VHF TRANSMITTERS IN THE EARLY 50'S. I BELIEVE THEY
> PUT OUT A  COOL 500 WATTS OF AUDIO.
>
> I BOUGHT THEM THIRTY YEARS AGO FROM A SURPLUS  DEALER IN ARIZONA (DAVIS
> MONTHAN AFB) WHO WAS MELTING DOWN PLANES FOR  ALUMINUM.
>
>
> THEY HAVE BEEN CAREFULLY STORED EVER SINCE.
>
> THESE  UNITS HAVE LARGE XFORMERS, CHOKES AND CAPACITORS AS WELL AS LARGE
> AUDIO  SECTIONS. THEY HAVE SWITCHED MONITORING METERS AND COOLING FANS
> THAT  HUSTLE AS BLOWERS.
>
> BOTH UNITS ARE BY COLLINS, BOTH HAVE LARGE POWER  SUPPLIES WITH POWER
> SUPPLY AND MODULATOR INTEGRATED IN THE SAME LARGE RACK  ASSEMBLY.
>
> THEY ARE COMPLETE EXCEPT THEY DO NOT HAVE ANY OF THE  TUBES.
>
> THE AUDIO FINAL TUBE WAS A LARGE TWIN, LIKE AN 832, BUT  HUSKIER.
>
>
> THE RECTIFIERS AS I REMEMBER WERE 2B28's.
>
>
> THE  CASE IS ALUMINIUM, CONFIGURED FOR NORMAL RACK MOUNTING.
>
>
> THERE IS A  FULL SCHEMATIC PRINTED ON THE UNDERSIDE OF THE TOP PANEL
> USING AN  ENGRAVING PROCESS WHICH I AM AT A LOSS TO DESCRIBE.
>
>
> THEY WEIGH  ABOUT 150 #'s
>
> WOULD LIKE THEM TO GO TO A GOOD HOME AND WOULD LIKE A  REASONABLE OFFER.
>
> TOO HEAVY TO SHIP, BEST TO PICK UP IN  PHILADELPHIA.
>
> W3AGR
>
> Thanks  W3AGR
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