[MRCA] Retransmit: was MRCA Meet Recon Patrol Operations
Gene Smar
ersmar at verizon.net
Sun Aug 26 12:46:37 EDT 2012
Al et al:
Here's a link, I think, to the duplexer you describe:
http://www.prc68.com/I/CU2194.html . It's just an antenna duplexer that
permits one antenna to be used simultaneously with two PRC-77's. The freq
sep required is 3 MHz. It does not, however, provide the connections that
permit one -77 to retransmit the audio of the second and VV. For that you
would need the CX-4656/GRC cable harness, below.
Also, if we did set up the two 6M freqs and retransmit each to the
other, we'd have to make sure that the two groups of stations, one on each
freq, could hear each other. Otherwise, there may be some stations that
could be heard (and retransmitted) by the repeater, but, because of their
low-lying location, might not be heard by other co-channel (e.g., 50.4 MHz)
stations nearby.
To try this mode at GIlbert we'd need a couple of good -25/-77s plus
bunches of other frequency-agile radios that can move to channels other than
51.0. I have one -25 that I usually bring. ANyone else?
QUESTION: Was this duplexer used onboard fixed-wing AC that relayed
infantry requests from a battlefield to artilery batallions out of normal
range of the PRC-77's in the battle zone?
Another thought just occurred to me, but a bit too late for this year:
we ought to mess around with some of the field telephones like the EE-8s.
I've frequently thought that these things might be handy to have around at
an EmComm event like a shelter or hospital (where I sometimes help out with
EmComm exercises.) For Gilbert we might consider having one inside near
Ted's radios and one outside in the campgrounds somewhere. Would be cool to
crank the ringer and have someone answer.
73 de
Gene Smar AD3F
----- Original Message -----
From: "Al Klase" <ark at ar88.net>
To: <mrca at mailman.qth.net>
Sent: Sunday, August 26, 2012 12:21 PM
Subject: [MRCA] Retransmit: was MRCA Meet Recon Patrol Operations
> 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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