Help understanding GRA-39's

[budman67]

The use of gra-39,do I hook up two lines on the front of the unit
to the other unit to have a sort of telephone set up?
I am referring to the two red points in the photo,would this
set up in the photo count as one unit or two?

If it is one,I would need another one to talk to?
I have been trying to get this TM 11-5820-477-12,
but all that I find is TM 11-5820-477-30.

 

[mkcoen]

I have limited understanding of the unit but from what I recall the set is for remote radio transmission in connection with a PRC-25 or RT426.

What you have is the C2328 (one with speaker) and C2329 (one with mike cord) which together make the GRA-39. You place the C2329 at a remote location and connect it to the C2328 with field wire and then connect the C2328 to a radio. This allows you to transmit from a location without having the radio signal come from where you are (basically hiding from arty).

I think you can still use it as a field phone without having it hooked up to a radio but am not certain on that point.

 

[CARNAC]

Yes that is one unit. The lower one is what you would put in you building/office/CP.

The upper one is what you would put with your radio. The 'curley cable' will attach to the same connector you would plug in your microphone handset.

You would use standard military radio cable to connect to the red posts (normally the ones I see are black rubber).

In over 20 years of service, I only saw these used twice other than testing them and instructing how to use them. I was told the intent was to enable a CP to move the antenna up to 1km away from their CP. This would put the eletronic transmissions from the antenna away of the CP. If the enemy picked up your signal, they would do any artillery strike against the antenna rather than the CP. It was also convenience for the simple fact you could leave a radio mounted in a vehicle up to 1km away and talk over the radio from inside the building.

 

[emmado22]

We used those things all the time in the big windowless musty building known as the SIM Center at Hood..........

 

[maddawg308]

Ditto what CARNAC said. They are much useful in this age when there could be the potential for signal triangulation, and the enemy possibly using heavy artillery to wipe your grid square off the map. They can actually be used up to 2 miles from the CP using standard 2-wire commo field wire. Set up your radio on the hilltop, run the wire down the ridge to your CP, and broadcast away...

I can vouch for 4 of these units lost in the Pine Barrens around Ft. Dix, NJ....

 

[mkcoen]

I have a friend that has 4 of the C2328 (one with speaker) if anyone is looking for one to complete a set. I'll get a price if someone needs one.

 

[budman67]

Let me put this in simple terms,the two units in the picture,I
could put the one with the curled cord and a handset at one
end,and the one with the speaker at the other end with a
handset with two wire cord joining them like two tin cans with
string.I don't need a radio for them necessarily?
Could I join more together with some sort of unmanned switch
board?

Thanks for the help,this was getting over my head.

 

[CARNAC]

I guess you could but why would you want to use these instead of TA312 field phones and a SB22 switchboard or SB93 switchboard?

 

[SCSG-G4]

For some, it might be the technical challenge, others it's the 'use whats available', but given my druthers, I would use the TA-43/TA-312's and the SB-22's (cause that's what I have available).

 

[budman67]

I was looking for gear to run with the PRC-77 radios,my knowledge
is limited to what I have read.But the fun part is,trying to figure it
out without anyone showing you how,I was getting a little lost.

I had to look up the TA-312,I'm not sure we used these up here in
the early 90's.It looks like a nice phone though,I might look for one
later. I would like build up my radio collection to include a base set
up,man patrol and vehicle mounts.

The next fun part will be figuring out how to hook it up.

 

[popacom]

WE OVERHAULED SEVERAL HUNDRED SETS OF THESE A
FEW YEARS BACK AT RECO DEFENSE. THEY ARE KINDA COOL
WHEN THEY ARE WORKING CORRECTLY ,BUT THEY CAN BE A
PAIN IN THE rrrrrrsss!!!!! I WAS THE ONLY ONE THERE WITH THE
PATIENCE TO ADJUST THE "CLACKERS" ............EARNED ME THE
SHOP NAME OF "DOCTOR CLACKER".............NOT MY FINEST HOUR LOL!!!

popacom / BILL in KY.

 

[SCSG-G4]

budman,
The TA-43 is the earlier version of the TA-312, without the extra connector for a second handset. All other functions are the same, and the -43's are usually a bit cheaper. For my purposes, they are the same. Both models have been found on the surplus market for over 20 years, maybe 30. I got my first ones surplus about 30 years ago.

 

[budman67]

I just started my adventure into military collecting,it is a very
expensive hobby.I am sure I will have lots of questions later
as I run into more trouble.

Thanks again

 

[budman67]

Has anyone here used the prc-77 range booster ?
I could not find the TM on my goggle searches. I
couldn't find out how to hook it up,prc68.com had
a write up one it.

 

[JoeyAirborne]

Sorry for flipping this up to the top.
Got a question about that GRA 39 set.Got one too in working condition.
I was told that the GRA39 could also be used attaching it to a switchboard. So that everyone conected to the SB is able then to contact radios just with a simple field phone.
Sounds interesting for me.So that every station inside a reenactment camp like kitchen motorpool or whatever can call out via there field phones the patrols and vehicles out in the field.

 

[CARNAC]

Without a TA312 or GRA39 here, I'm trying to picture this working.

Signal comes into the radio to the radio end of the gra39 to the cp end of the gra39 with an extra line of commo wire going from the hookups at that part of the gra39 to the sb22 to all the phones in the field site. There's where my thought process goes south. So how do the folks hear it there? Does someone have the phone receiver pinned to their ear at all times? Is there a loudspeaker that attaches to a TA312? I've never seen one. I'd also have some concerns from a tactical/operational standpoint for everyone to listen in on radio conversation.

I'd also have to ask when the radio signal is converted into phone signal? Does the GRA39 actual do that?

I guess once I get all my stuff together in about 10 year (LOL) I can test this out.

 

[m38inmaine]

I had one of the range boosters it's about 30watts output. Mine had a 24vdc connection on the back instead of a battery box. You use a short jumper cable with bnc connections on both ends, connect the radio "ANT" to the booster "IN" and then hook your antenna to the booster "OUT" or thread a whip in. If you have a tuneable antenna base you hook up tuning cable to the tuner connection. I think mine was an AM-4477, it attached to the back of the RT with a band clamp.

 

[JoeyAirborne]

Yep thats my thought that the local control attached to the radio (in my case PRC25 or 77) hooks via field cable to the remote control unit.The remote control then is conected to the SB 22 but not through the same field cable lines. I think i have to split up a U/182 conector from the remote and attach it to the SB 22.From there the SB 22 Operator can call through to every fieldphone to guide the connection to the end fieldphone like any call he through the SB 22.The same operator allready gets the calls through the remote because of the clacker and loudspeaker in the remote control.

They guy who told me it, explained me he will send me his TC24-19 Radio Operators Handbook.It is explained in there how this works.The whole thing is called Remote Control Net Radio Interface (NRI).

But if i think of it well if this works with a GRA 39 then this is also working with the old GRA 6 for old Nato U/77 conectors.PRC 8/9/10 or VRC and GRC systems.That would be also interesting because i dont have to keep one PRC25 back in base and give them all out to the patrol Rto`s.

 

[tennmogger]

Has anyone here used the prc-77 range booster ?
I could not find the TM on my goggle searches. I
couldn't find out how to hook it up,prc68.com had
a write up one it.

I use the AM-4477. Check it out on the left side of the picture. The attached picture was at the Georgia SS Rally a couple of years ago. I moved the radios to the rear of the 404 Unimog radio box because it's hot inside, and I got tired of getting in and out.

One big advantage of using the AM-4477 with a PRC-25 or 77 is that the AM-4477 samples the RF signal from the radio and determines the correct setting for an attached antenna like the AS-1729 with MX-6707 matching unit. The PRC-77 by itself does not provide this switching capability. The AM-4477 has the connection for cable CX-4722A/VRC going to the antenna. A big disadvantage of using the PRC-77 with the AM-4477 is that the former is 12v and the latter is 24v. I didn't have the mount and power supply that resolves that issue.

BTW, the other radio in the photo is an Israeli PRC-174 HF packset, 2 to 30 MHz. The big radio back on the radio operating bench is an SEM-25 tactical (vehicular mount) VHF transceiver that was originally issued with Unimog radio trucks (25 to 69.95 MHz)

Bob WB4ETT

 

[papakb]

GRA-39 TM s sent today.

Kurt