RT-246 Military VHF Low Band Vehicle Radio, VRC-12 Family

Brooke Clarke 2009 - 2010


RT-246 Military VHF
        Low Band Vehicle Radio VRC-12 Series
Background
Spares
Test Equipment
    VRM-1
Links

Background

This is one of the VRC-12 series Military VHF low band vehicle radios.  The others are the RT-524 ( very similar to the RT-246 but w/o the pushbutton tuning and w/speaker) and the R-442 receiver.  It interoperated with the PRC-25, PRC-77, PRC-68, PRC-68A, PRC-68B, PRC-126 and the low band version of the PRC-128.  It also has provision for communications security be adding an external KY-38 or  KY-57.

I got this radio for the GRC-206 system which was designed to allow remote channel selection.  It fits into the lower right corner of the MT-6250 equipment rack.

This radio is in the VRC-12 family and works with the Vehicle Inter Communication (VIC) equipment

Spares

These parts came from an RT-524 and many of them are common to the RT-246.

Note:  The RT-823/ARC131 uses some of the same modules as the RT-246.  I expect the R-442 and RT-524 also have common modules, i.e. most of the VRC-12 family.



VRC-12 Spares
VRC-12 Spares
VRC-12 Spares
VRC-12 Spares
VRC-12 Spares
VRC-12 Spares
VRC-12 Spares
VRC-12 Spares
VRC-12 Spares
VRC-12 Spares
VRC-12 Spares
VRC-12 Spares
VRC-12 Spares
VRC-12 Spares
VRC-12 Spares
VRC-12 Spares
VRC-12 Spares
VRC-12 Spares


Test Equipment

AN/VRM-1 NSN: 6625-00-892-5542

Major Components:
TS-1777 Test set
MX-7899 "Y" cable

The probe contains an AC coupled RF amplifier and a choke isolated DC line so can be used for both types of testing.  All solid state construction.

AN/VRM-1 Panel
TS-1777/VRM-1
AN/VRM-1 Lid
Notice the spare lamp and probe tip in the upper left corner.

The instructions are divided into sections:
  • Generalized Test Procedures
  • Audio Assy A5000
  • IF Assy A4000
  • Crystal Ref System A3000
  • Modulator Assy A8000
The switch position determins the type of measurement and test limits.
Where the probe is placed determines what gets measured.
So for a given assembly there may be multiple tests with the same switch
position on different test points.
VRM-1 Y Cable
VRM-1 Y Cable

The large MCM block connector plugs into the back of the radio.

The large round connector plugs into the three sockets on the right of the MT-1029  MCM block connector.  (Note the large round connector can be plugged into the MCM block connector (A, B & C) on the cable. the the mating terminals are wired 1:1)   B&C on the large MCM connector are tied toghther and to to either pin B on the small circular connector. 
Pin A on the large MCM block goes to either pin A on the samll cir conn.

MCM
Block
MCM
Cir
Small
Cir
Function
A
A
A
Ground
B & C
B & C
B
+24 VDC


 The small circular connector plugs into the VRM-1.

VRM-1 Manuals

TM 11-6625-496-12
TM 11-6625-496-20P
TM 11-6625-496-45 Field & Depot Maint (w/schematics)
TB 11-6625-496-35 Cal Procedure for Radio Test Sets, 12 pgs

U.S. Army Training Film

RADIO SET AN/VRC-12 (1963) TF11 3305, 1963

Links

Pvt Jar Head - RT-246
eBay - spare parts
Fair Radio Sales - VRM-1


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page created 14 June 2009.