[MRCA] crossband 51.0 to VHF

Gene Smar ersmar at verizon.net
Sun Aug 30 21:12:21 EDT 2009


Al:

     I haven't looked in my PRC-25 manual yet, but I suspect that putting 
either the -25 or -77 in the retransmit mode puts an audio tone on the 
outgoing AF signal that is used to internally key the PTT line of the other 
radio.  I further suspect that there is a unique cable assembly that will 
connect both U-183 connectors (mic/phone connectors) on the two radios. 
These two radios share a common antenna via the duplexer you mentioned below 
(actually, it's a CU-2194 DI-plexer.)  I'll do some reading tonight in my 
TMs and see what I can learn.

     Another thought:  None of the milrads we typically use in the field is 
capable of operating with offset TX and RX.  So this retransmitter we're 
thinking about will repeat one simplex channel onto another.  That is, 
radios around Gilbert can use 51.00 MC and get into the retransmitter, but 
the retransmitter must set its other radio's simplex channel to, say, 53.50 
MC.  The distant milrads will have to talk to (and listen to) the 
retransmitter on this other freq.

     I believe this function came about when the -25's and later, the -77's, 
were set up with 2 channel presets for patrols.  One simplex channel was for 
local comms, much as we use it during our field ops.  The other preset 
channel was to talk through a fixed-wing acft orbiting overhead and relaying 
requests for artillery, etc. to the base beyond the backpacks' range.  The 
orbiting plane had the diplexer you mentioned (CU-2194) plus two -25's 
or -77's set on the two simplex channels, plus the requisite external 
antenna.  Both the patrols and the artillery RTOs used simplex channels, but 
talked to each other through the flying retransmitter.

     BTW:  Can't we simply set up two -77's, in retransmit mode on a 
hilltop, cable their audio sockets together and use their flexible whips 
instead of the diplexer?  The diplexer simply lets us use one LB VHF antenna 
for the pair.  Or have I overlooked something?

73 de
Gene Smar  AD3F


----- Original Message ----- 
From: "Al Klase" <al at ar88.net>
To: "Ray Fantini" <rafantini at salisbury.edu>
Cc: <mrca at mailman.qth.net>
Sent: Sunday, August 30, 2009 7:23 PM
Subject: Re: [MRCA] crossband 51.0 to VHF


> Hi Ray,
>
> How about a PRC-77 in "RETRANSMIT" mode?  There's a whole bunch of
> things I don't know here.  I also have one of the Marine Corps. LO-VHF
> duplexers, so I guess we could run two 77's as an in-band repeater.
> However, I fail to understand how one would take advantage of such a
> setup without having something like an RT-524 + R-442.
>
> Are all the U-229 retransmit connections the same?
>
> Al
>
> Ray Fantini wrote:
>> If , and the key word is if anyone has a URC-104 and can bring it I will
>> bring a URC-110 and a duplex cable that allows the two radios to operate
>> as a cross band repeater. The 110 will operate in the two meters “Ham”
>> band and the 104 will operate on 51.0 always wanted to try that out. I
>> have a URC-110 and 101 and have played around with the repeater option
>> before but don’t have a URC-104 for the Low band stuff. Am planning on
>> bringing one URC for VHF AM operation so their will be at least one
>> working VHF AM set on a known frequency!
>> Ray Fantini KA3EKH
>>
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> -- 
> Al Klase - N3FRQ
> Jersey City, NJ
> http://www.skywaves.ar88.net/
>
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