Vehicle Mounted PRC-77 Sets

[JD Baillie]

The AN/PRC 510 set ( the Canadian version perhaps?) was capable of Radio Rebroadcast functions. It took two radios and a linking cable. Similarly the 25/77 set was also capable of this function. While I can't remember about the 510 cable, the 25 set RRB cable had a centered relay. Both setups needed to be about 25 feet appart. Possibly in the early days of Vietnam the older prick 10 was kept in the rear while the newer 25 set went forward. ??

When vehicle mounted the 25/77 set became the 125.

On another historical note Jimmy's became known as 'Zero Beats' due to the tuning tone of the 510.

JD

[phoenix]

A mounted 77 set with full ces is a AN/GRC-160 actually

[JD Baillie]

OK. So why did we call it a 125? Was that the original 25set name?

JD

[rob love]

It's like splitting hairs really. The 25 and the 77 were not identical radios according to this site:

http://www.olive-drab.com/od_electronics_anprc25.php

AN/PRC-25 and AN/PRC-77 in Other Configurations

There were three basic configurations of the PRC-25: starndard manpack, vehicular (called AN/VRC-53 in that configuration), and dual manpack or vehicular (AN/GRC-125 configuration). The PRC-77 also had these combinations available, but with different nomenclature as explained in the following.

AN/VRC-53 components AM-2060 Power Supply and Mounting Tray
AM-2060 Power Supply and Mounting Tray. Click image for view of complete AN/VRC-53 system.

AN/VRC-53 Radio System refers to RT-841/PRC-25 when installed in the AM-2060 Audio Amplifier/Power Supply and connected to the AS-1729/VRC Vehicular Whip Antenna. The MT-1029 Vehicle Mount is used to install the AM-2060 in a vehicle. The MT-1029 also supports use of the VIC-1 Vehicle Inter-Communication system.

AN/VRC-125 dual purpose system (vehicular or manpack) includes the vehicle set up as above, plus the ST-138 web suspenders back pack, battery set and the CW-503 accessories bag.

The AN/PRC-77 is the basic receiver-transmitter equipment used in the vehicular sets AN/VRC-64, AN/VRC-65 and AN/GRC-160.

The AN/VRC-64 is the vehicular version of the RT-841/PRC-77 portable Radio Set, consisting of: Receiver-Transmitter mounted on the Amplifier-Power Supply Group OA-3633/GRC. It also includes the AS-1729/VRC Vehicular Whip Antenna.

The AN/GRC-160 consists of an AN/PRC-77 Radio Set, including all the vehicular components covered above and as noted in the AN/VRC-64 as well as all standard Manpack accessory items. The AN/PRC-77 can be removed from the vehicle and used as a battery-operated Manpack Unit and later returned and mounted back onto the OA-3633/GRC resuming vehicular operation.

So the jist of it is a 25 in the AM 2060 tray (along with the remainder of the installation) is a AN/VRC53, whle a 77 in the 2060 tray with IKEE is a AN/GRC-160. The AN/GRC 125 is a AN/VRC53 setup with the regular manpack components issued alongside.

Thank god I use a 524 set so I don't have to remember all this.

[JD Baillie]

Rob,

If you're a 524 guy then we get to ask you about 46 sets.

Easier if you just worked on a CLAK like a normal 052.

JD

[Craig Tanner]

This is what I know... which may be very little.. but I certainly have a few nights carrying around both the 25 and 77 set man pack boat anchors...

I always knew the PRC 25 set was an older version, and the ANPRC 77 set was newer. It was reported to have had updated electronics, and a breather mounted on the battery cover. Other than looking at the tag where the serial number was (which stated 25 or 77 set) the breather was a sign of the .... 77 set.

For the RRB function, in a vehicle, the dual installation system either 2x 524s or 2x841s (77s in trays) you needed a thing called a 2299 box which, when engaged on RRB allowed the radio net to be rebrodcast.

That was a couple of years back so I may be a little rusty on some of the more complex terms like RT841/77PRC etc but I will never forget that radio.....

I'll see if I can dig up some pictures....


For all its worth

Craig Tanner

[maple_leaf_eh]

The '77 manpack harness fits nicely over the passenger seat of the M38A1 jeep. Tilt the seatback and judiciously arrange the pressure points. The 10' antenna mounting unit cable (forget the name) normally connecting the AMU to the RT524 also connects to the '77. I prefered the handset of the '77 set hitched onto the '524 versus the headset and mike combination. Fewer loose pieces and it used one headset plug-in vs two. Or, keep the '524 on one freq' and monitor another on the '77 with its 10' antenna.