[MRCA] Retransmit: was MRCA Meet Recon Patrol Operations

Sun Aug 26 12:21:29 EDT 2012

Hi Gene,

I get the impression that a pair of transceivers connected for 
"retransmit" might be paced on a ridge.  Station on one side of the 
ridge would operate on, say, 50.4, and stations on the other side would 
operate on 53.9, and everybody could communicate with everybody.  This 
is different from normal amateur "repeater" practice where the user's 
transceivers are operated in split-frequency mode.

I have some sort of box out in storage (50 miles away)  that appears to 
connect two sets for retransmit, and contains filters, that, I think, 
allow use of one antenna.  It was never clear to me what the minimum 
allowable frequency spacing was.  Does anyone know the nomenclature for 
this box?  It's about the size of a PRC-77, and might have been Marine 
Corps stuff.

Perhaps we should play with this mode at Gilbert, even if we don't set 
the thing on a ridge.

Al

On 8/26/2012 11:58 AM, Gene Smar wrote:
> Gents:
>
>       FWIW:  There is a special cable that is/was used with a pair of
> PRC-25 -77's to retransmit audio from one to the other.  The cable includes
> a connection that utilitizes the grounding of pin E of the connector from
> the opened squelch to activate the PTT of the other unit.  Could one
> possibly use this same signal on pin E to activate the PTT of another,
> non--25 or -77 radio?  And vice versa?
>
>       Here's the e-mail I wrote on the subject on August 31, 2009:
>
> All:
>
> After a bit of reading in my TM for the PRC-77 I see that the
> CX-4656/GRC cable assembly uses Pin E in one radio's connector to pull to
> ground the PTT line in the opposite connector when the first radio's squelch
> opens. Pin E becomes active in this way when the -77 (and -25, I assume) is
> placed in retransmit mode. The cable assembly includes a box that has small
> capacitors to ground and steering diodes for the PTT lines, plus
> inductors/chokes in series with all lines (audio and control.) Should all
> be easy enough to fabricate if one wanted to.
>
> There is one issue with using this assembly with two -77's in
> retransmit mode: The two antennas and their TX freqs must be far enough
> apart that desense is minimized. The TM recommends a minimum channel
> separation of 3.5 MC (physically, the units with their antennas are to be
> placed 50 feet apart - the length of the cable.) For us to be able to use
> this technique at Gilbert or elsewhere we would need one freq just below 54
> MC (say, 53.90) and another at around 50.40. This is permitted by FCC Rules
> but it eliminate 51.00 from possible use.
>
> That's enough for tonight. G'night, all.
>
>
> 73 de
> Gene Smar AD3F
> ----- Original Message -----
> From: "Ken Downs"<krtdowns at myfairpoint.net>
> To: "W2HX"<w2hx at w2hx.com>
> Cc:<mrca at mailman.qth.net>
> Sent: Sunday, August 26, 2012 8:51 AM
> Subject: Re: [MRCA] MRCA Meet Recon Patrol Operations
>
>
>> Back in 1980-82 when I was stationed at Ft Lewis, WA with the SHORAD
>> battalion (1/67th ADA),  a higher HQ ran a division-wide air defense
>> warning net using a crossband setup. They tied an RT-524 VHF rig and a
>> GRC-106 HF rig together somehow. It worked pretty well, but I think it was
>> one-way cross-band - VHF in and retrans out on HF until they figured out
>> how to get the HF rig to key the FM set. I believe the GRC-106 has no
>> squelch, or if it does, they could not get things going very well
>> HF-to-VHF. They may have eventually come up with a custom outboard VOX
>> box. I was not directly involved with it and do not remember how they did
>> it. The concept was brought to Germany for a test (along with some other
>> stuff) during an exercise at one point and seemed to work pretty well.
>> Might be fun to play with using two back-pack rigs.
>>
>> Ken, W1KRT
>>
>> On Aug 25, 2012, at 3:25 PM, W2HX wrote:
>>
>> Ok, I've never attempted the retransmit idea, but I'll see if I can figure
>> something out between my HF sets and VHF set (PRC-119 with or without amp)
>>
>>
>> 73 Eugene W2HX
>>
>>
>> -----Original Message-----
>> From: mrca-bounces at mailman.qth.net [mailto:mrca-bounces at mailman.qth.net]
>> On Behalf Of Radio Station KW1I
>> Sent: Saturday, August 25, 2012 3:19 PM
>> To: mrca at mailman.qth.net
>> Subject: Re: [MRCA] MRCA Meet Recon Patrol Operations
>>
>> Gene, Eugene and Al
>>
>> Al is correct.  The 51.1 mHz is a typo.  FM liason comms will be on the
>> 51.0 mHz frequency we have used in the past.
>>
>> Eugene,
>>
>> If you can engineer the HF to 6 meter link, go to it.  It would add a new
>> dimension to our "scientific inquiry" efforts.  I think most if not all
>> the stations will be able to copy each other on HF if we have good NVIS
>> conditions.  As Al reported Penns Peak and Big Pocono have line-of-sight
>> to the fairgrounds.  Beltzville can copy both Penns Peak and Pocono and if
>> I recollect some ability to get into the fairgrounds.  Lake Minsi and
>> Jacobsburg are pretty isolated on 51.0 and may have no FM comms to any
>> other station.  FM coverage comments from previous MRCA radio ops at those
>> sites are invited.
>>
>> Dale
>>
>>
>>
>>
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-- 
Al Klase - N3FRQ
Jersey City, NJ
http://www.skywaves.ar88.net/