[Milsurplus] ACR-5 Mobile

[Jack Antonio]

There are 12V dynamotors that will fit on the receivers with no mods, 
but then there
is the issue of filaments and all the relays in the receiver rack and 
modulator. AFAIK
there is no 12V dynamotor that will be a plug and play equivalent for 
the modulator.
(Although I suppose you could mount the 12V dynamotor for the BC-604/684
on a DM-33 or DY-? base). I have heard stories about the relays being 
rewound with
the next size larger wire, the antenna relays have two coils, which could be
rewired to work on 12V, so there are ways to convert the set to 12V, just
depends on how much alteration you wanted to do.

There was some mention on the web about a police department that converted
SCR-274Ns to 12V(in New Zealand, IIRC), but no technical details.

My solution would be to try one of the newer solid state 12V to 120AC 
inverters and
use a regular 28VDC 20A power supply. Leaving the radio itself in stock 
configuration.

As far as power out goes, on CW I've always been able to get at least 
25W out of
a stock transmitter(using the stock dynamotor), but on AM the screen voltage
is lowered, which brings AM power down to 15 watts or so.  I can see why
this was done on the SCR-274N with its screen modulation, but I guess when
the AN/ARC-5 was being designed, higher AM power was just not a requirement.
Thinking about it, these were short range sets, 15 watts may have even been
the maximum power the Navy wanted.

Jack

Jack Antonio WA7DIA
scr287 at sbcglobal.net



Al Klase wrote:
> Troops,
>
> I'm starting to contemplate taking a stock AN/ARC-5 mobile so people 
> can see and hear it.  This would be a single transmitter and receiver, 
> probably on 75 meters, plus an MD-7 modulator, RE-2 antenna relay, and 
> control boxes as needed.  I have all of above, but need a single 
> transmitter rack and mount, MT-68/69.
>
> Does anyone know the actual output of the TX?  Manual sez 15 watts 
> carrier, but I suspect a pair of 1625's with 550 on the plates should 
> do at least twice that.
>
> Also, there the issue of primary power.  I'm looking for a good way to 
> get 28 volts at about 10 amps from 14 volts with enough reserve to 
> spin up the TX dyno.  I don't suppose anyone has 12/14 volt dynomoters 
> for MD-7 and RX lying around?
>
> Any help or suggestions appreciated.
>
> Regards,
> Al
>
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