MT-1029 Radio Mount

© Brooke Clarke, N6GCE

Background

Install Kits

VRC-12 Cables

Military Vehicles use a standardized cable for supplying 24 Volt vehicle power to onboard equipment.  It consists of a 4 pin connector with a central anchor screw driven by a folding flap to allow connection and removal without tools.  It's completely different from the common MS series circular connectors, thus avoiding confusion.

DC Power

The MW series are very common vehicle DC power connectors.

From Vehicle Battery MW10F(M)Axx
Input to Equipment MW20M(M)A00	Output from Equipment MW20F(M)A00	Panel connectors have fixed male threaded posts

DC Power Cable Note

The CO-04MOF cable is rated for 21 Amps max. according to a cable supplier.  I don't know if this is exceeded on some duty cycle basis like the ratings for a transmitter where it's on for 1 minute and then off for 9 minutes.  What's the largest load you know of in Amps fed by a CX-4720 or CX-4723?

The RT-246 and RT-524 pull 10 Amps on high power transmit, so a retransmission setup, where only one radio is transmitting (the other will be receiving) will draw maybe 12 amps, not even 20 Amps.

Also the life of the early cables is very long while still in the government packaging, but after exposure to air and temperature cycling it's 8 to 10 years.  If the cable feels tacky or spongy it needs to be replaced.

CX-4720 Wire Ends (Battery) to Radio Power Cable	Has a 4 socket connector on one end and wires on the other end.  Typically used to connect from a 24 Volt battery to a radio Mount.  The cable: 4 each # 14 stranded wires.  Pin Wire Function A Black & Green Negative B Red & White Positive C D maybe gnd for On CO-04MOF(4/14)0500 MIL-C-3432E. The Connector: MW10M(M)D 17, MIL-C-55181,  M55181/7-03,  55181-1249-85, 20 mV drop at 35 Amps for 4 contacts.  This current rating is for the connector, not the cable assembly.
CX-4721 Radio Mount to Radio Mount Power Jumper Cable	This is a four conductor extension cable typically used to daisy chain Radio Mounts. The female connector is the same as on the CX-4720. The four pin Male connector: MW10M(M)A17,  M55181/3-03
	Note both connectors have female center threaded holes.
Antenna Cables
CX-4722 MX-2977 or MX-6707 Antenna Base Frequency Control Cable	This is a 12 contact cable that connects between an antenna base and either a radio or the AM-2060() for the purpose of controlling the operationg frequency band of the antenna base. Right Angle connector: U-393/U 12 Pin Plug.  Note in bag: Type U-393/U connector (Item 2) of the cable assembly has been polarized at 180 degrees.  The user may change this keyway and cable relationship by loosening the three connector flange 1/16" Allen screws and rotating the housing to the desired angle.  After repositioning, tighten screws securely. Cable: MIL-C-3432E, CO-12LOF(12/22)0350 12 conductors of 22 AWG. Straight connector: U-290/U, 12 socket Plug. Different cable, for R-1518/URR-71 is marked: CX4722A/VRC (6Ft, 0 In) DLA400-79-F-5228 Mfr 55923
CG-1773 BNC Coax Antenna Cable	Like the CX-4722 this cable comes in different lengths. The suffix letter is the key to the length.  This is a "B" suffix and is 6 feet 0 inches long.
Control & Audio
CX-4723 Power, Control & Audio Interconnect Cable	This is the cable that's used between the VIC-1 Intercom system AM-1780 Amplifier and the remote control boxes. It's very similar to the SINCGARS CX-13292 but they are wired differently.

VINSON Voice Encryption with Mounts MT-1029 or MT-1898

When the KY-57 is used in a VRC-12 Series installation special Junction Boxes are inserted between the Base mounting and the Tray of the MT-1029 or MT-1898.  These junction boxes contain a number of relays and a low power audio amplifier. They are designed to meet TEMPEST requirements.  A KY-57 is needed for each radio so for example a VRC-12 system needs two KY-57s and a VRC-48 needs three KY-57s.

J-3513 Box

Is installed with the box pointing down (labels read correctly)  inside the MT-1029 with the extended AUDIO connector pointing to the front.

Installing the J-3513 into the MT-1029

1. Use a 1/2" wrench to remove the 5 each 5/16-24x1" bolts from the top of the equipment tray.
2. Either disconnect the ground strap from the equipment tray, or when installing the J-3513 do not trap it.
3. Remove the SC-C-930707 Clamping Plate from the J-3513 by unscrewing 4 each #2 Flat Head Philips screws and set aside.
   
4. Install the J-3513 between the equipment tray and the base of the MT-1029 with the extended  AUDIO connector (J5) pointing to the front and the box portion pointing down (labels are right side up).  Be sure the sheet metal tabs go into the notches and all the parts are seated properly.
5. Re-install the SC-C-930707 Clamping Plate being careful to properly position so it clamps the equipment tray.
   
6. Use 5 each 5/16-24x1 1/4" bolts from the MT-1029 Install Hardware bag and the flat washers that were under the original bolts to install attach the equipment tray back to the MT-1029 base.  Do NOT use the lock washers in the Install Hardware bag, doing so will result in the bolt heads protruding above the plane of the equipment tray.  Instead put a drop of Loctite 222MS on the bolt.
7. After tightening the bolt check with a straight edge to be sure the bolt head is below the equipment tray surface and will not rub on the radio.
8. If you disconnected the ground strap in step 2, reconnect it now.
9. Plug the connector on the cable coming form P1 on the J-Box into J22 on the MT-1029 and tighten the wing handle until it's snug and the long axis is aligned with a pair of the notches so that when it's folded flat it will engage the notches.

J-3514 Box

Is installed with the box pointing down (labels read correctly)  inside the MT-1898 with the extended AUDIO connector pointing to the front.

VINSON Cables

For more on the VRC-12 & PRC-77 VINSON cables and Junction Boxes see the USM-481 VINSON Interconnect Tester web page.

SC-D-691342

The large support assembly or Hutch surrounds the PRC-77, RT-246 or RT-524 and it's top surface provides a place to mount one or two KY-57 boxes in MT-____   mounts.

Test Equipment

Documents

VRC-53 & VRC-64, GRC-125 & GRC-160 Manuals

PS Magazine Articles

Sources

Links

page created 16 March 2004.