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MX-7777 use

2nd Cav Trooper

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Hamilton, Ohio
I have a M151 with a RT-246, R442 and a VIC1 system. I have seen others posting about having to install a MX-7777 suppressor in the system which I did not do when I originally installed the equipment. I have found a MX-7777 and ordered a power cable but, before I get any further down the road, I would like to know if I actually need this device? It will be a major task to reroute and install new cables to access the MX-7777 as there is no place to install it that is convenient for use other than up front in between the seats.
 
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2nd Cav Trooper

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Hamilton, Ohio
Knew some folks in 2/2 Cav. when I was in Bamberg. Was in Nürnburg a few weeks ago, and almost anything to do with the HQ and Kasserne is gone, or so changed, you would be hard pressed to know what it was. Sad, sad. But time goes on.
I had heard that what was left was a immigrantion office or some such. It is sad, I had a good time serving there. Lots of good memories of Nurnburg.
 

Crapgame

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M151A2 was 2nd military wheeled vehicle I drove. I recall both the RT-524/MT-1029 as VRC-12 and PRC-77/AM-2060 VRC-64 systems in use on the M113A2 based tracks, the MX-7777 right over the Driver's left shoulder, to switch off before starting the track, the big yellow and black decal on the instrument panel being an easy reminder.

But I don't recall seeing an MX-7777 on the M151A2, stateside. It is not a big effort to reach back to flip the power switch on the radio mounted on the curb side rear fender top. I think when dealing with forward deployed units the KY57 TSEC VINSON encryption device comes into play, the KY57 would be nearly impossible to reach the tiny rotary power switch, it doesn't shut off when you power off the radio, it draws power direct from the MT-1029 through the "J Box". Incorporating the MX-7777 Suppressor would allow the drive to shut commo down prior to starting without having to crawl all the way to the back corner of the rear fender to shut off the KY57.

TM 11-5820-498-12-HR is the Hand Receipt covering AN/VRC-64, it does not list an MX-7777 as an accountable item on the inventory list on Page 13.

MX-1244/VRC-46 would be the installation kit for the VRC-64, does not list an MX-7777 as a component on Page 14.

The secondary PRC-77 vehicular installation is the GRC-160 the difference being the inclusion of the Manpack-specific components(ST-138 Radio Carrier[or ALICE Radio Ruck later], AB-591 Antenna Base, AT-271 Whip Antenna, AT-892 tape antenna with spring adapter base, and accessories bag) to allow the crew to continue to utilize the radio when the track was disabled. Or in our case, when we humped the 81mm mortar attached to the dismounted Rifle Platoons.

Slightly different utilization, in Berlin Brigade Feb 89-Dec 90, we had 3 Humvees assigned to the M125A2 track mounted 81mm Mortar Plt in the Rifle Company, 1each 4 door for the Plt Leader, 1each 2 door for the Plt Sergeant, and another 2 door for a Fire Direction Center FDC vehicle, which had several modifications, a map board on the wall and wooden benches with storage for the FDC guys to sit on while operating the M23 Mortar Ballistic Computer. And there were 2 of the VIC-1 Crew Boxes installed in the rear to allow the FDC to monitor and transmit over the VRC-64 radio system with headsets. And I seem to recall an MX-7777 behind the B Pillar curtain to shut down the PRC-77 radio and KY57 VINSON from the back.


2nd tour back in Berlin, Oct 1992-June1994, there was a new MTO&E, there were no longer track mounted 81mm M29A1 Mortars in the Rifle Companies or 106mm/4.2in M30 in the HHC, it was all HMMWV transported, ground mounted M252 81mm and M120 120mm Mortars, still no SINCGARS yet, I didn't see my first RT-1439 SINCGARS until my last 9 months at Ft Carson before I ETSed in 1996.

So officially, there are examples of the MX-7777 being used in some cases on wheeled vehicles employing PRC77 or RT524/246 radio systems in vehicular power adapter mounts and power amplifiers.

After posting, I googled the actual VRC-64 TM 11-5820-498-12, on Page 43 second column near the bottom, it states "The Electrical Transient Suppressors MX-7778/GRC or MX-7778A/GRC is provided in tracked vehicles to protect the radio equipment from electrical transient voltages that may be in the vehicular electrical system. Instructions for installing the installation kit for the MX-7778/GRC and MX-7778A/GRC are provided in TB 11-2300-457-30"
 
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2nd Cav Trooper

New member
14
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Location
Hamilton, Ohio
Thank you, I just talked to a friend who told me that the Air Force radio mutts used them and mounted them right behind the drivers seat on the right so that the drive could reach back and turn them on or off as needed. I am torn since if I mount one I have to acquire and reroute cables which are a PIA. and $$. I may just drop the idea.
 

Crapgame

Well-known member
635
329
63
Location
Navarre, FL
Thank you, I just talked to a friend who told me that the Air Force radio mutts used them and mounted them right behind the drivers seat on the right so that the drive could reach back and turn them on or off as needed. I am torn since if I mount one I have to acquire and reroute cables which are a PIA. and $$. I may just drop the idea.
I think the short answer is, there is evidence the MX-7777 was used on wheeled vehicles in some limited applications, not as a standard installation. So if you WANT to install one, to recreate a specific vehicle application or for operator convenience, then go ahead and do it. But it isn't a required component.

USAF....I drove M151A2 in the NJARNG HHC (4.2 Plt) 3/102nd Armor 50th DD. There were USAF JTACs attached to Infantry Divisions, the ones I saw were obviously HMMWVs when I went on active duty, the famed "shark-finned" HMMWVs. Before that they had the M151A2 MRC-108 commo jeeps with the various FM radios to connect with the ground elements they supported and VHF/UHF radios for talking to the aircraft they guided onto targets to support the ground forces mission. Matter of fact here's an article somebody wrote on the USAF TACP Mutt Jeeps: This Cold War Jeep Packed Mean Horsepower in Its Comms Array, but Not Under the Hood - autoevolution
TACP Jeep2.jpg
The Marines, having ground support aircraft as an integral component, have their own FM/VHF/UHF radio jeeps now HMMWV.
 

Attachments

2nd Cav Trooper

New member
14
13
3
Location
Hamilton, Ohio
I think the short answer is, there is evidence the MX-7777 was used on wheeled vehicles in some limited applications, not as a standard installation. So if you WANT to install one, to recreate a specific vehicle application or for operator convenience, then go ahead and do it. But it isn't a required component.

USAF....I drove M151A2 in the NJARNG HHC (4.2 Plt) 3/102nd Armor 50th DD. There were USAF JTACs attached to Infantry Divisions, the ones I saw were obviously HMMWVs when I went on active duty, the famed "shark-finned" HMMWVs. Before that they had the M151A2 MRC-108 commo jeeps with the various FM radios to connect with the ground elements they supported and VHF/UHF radios for talking to the aircraft they guided onto targets to support the ground forces mission. Matter of fact here's an article somebody wrote on the USAF TACP Mutt Jeeps: This Cold War Jeep Packed Mean Horsepower in Its Comms Array, but Not Under the Hood - autoevolution
View attachment 904205
The Marines, having ground support aircraft as an integral component, have their own FM/VHF/UHF radio jeeps now HMMWV.
 

2nd Cav Trooper

New member
14
13
3
Location
Hamilton, Ohio
Just for S&G's I searched for the installation manual TB11-2300-457-30. I found it on Survival Ebooks and through $2 bucks at it to download. What a rip, most of the pics were broken, couldn't open and the one that was visible was so small it couldn't be read. No way to blow it up. Just beware. I'm probably not going to install the MX7777 in the MUTT. Too much trouble and evidently not needed. Thanks again for all you input.
BTW, Fair Radio is closing permanently at the end of the year.
 
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