[Milsurplus] ACR-5 Mobile

Fri Sep 7 17:00:26 EDT 2007

The TX and RX tubes should be able to be rewired
in parallel vice series for 12V filament operation.  No
other changes should be needed if B+ is correct!

Mac - K2GKK/5
Oklahoma City

----Original Message Follows----
From: telegrapher at att.net
Reply-To: telegrapher at att.net
To: Jack Antonio <scr287 at sbcglobal.net>
CC: Boatanchors <boatanchors at theporch.com>,Military Radio Collectors 
Association <mrca at mailman.qth.net>,Al Klase <al at ar88.net>, milsurplus 
<milsurplus at mailman.qth.net>
Subject: Re: [Milsurplus] ACR-5 Mobile
Date: Fri, 07 Sep 2007 13:56:51 -0700

If you've got a 12V dyno and use 6V tubes in the receiver, won't that work?  
I've bought receivers that had the 12V dyno's and loaded with 6V tubes.  
What's wrong with that?.

Remember i didn't say anything about the transmitter or modulator, only the 
receiver.  Seems i recall seeing a write-up with a picture or two from way 
back showing an arc/SCR-274n setup in a car as a mobile rig. Don't remember 
any of the specifics but i suspect that there was considerable mod work done 
on it.  Either the receiver or transmitter rack which was a double unit had 
been sawed in half but that's about the extent of my memory recall cells.

Larry
W0OGH

Jack Antonio wrote:

>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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>
>
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