[MRCA] Retransmit: was MRCA Meet Recon Patrol Operations
Al Klase
ark at ar88.net
Sun Aug 26 12:45:33 EDT 2012
Disregard question about box identity. It's a CU-2194/URC.
See:
http://www.bpbsurplus.com/lc/cart.php?target=product&product_id=17433&category_id=333
<http://www.bpbsurplus.com/lc/cart.php?target=product&product_id=17433&category_id=333>
Al
On 8/26/2012 12:21 PM, Al Klase wrote:
> 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/
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