M35 Commo Truck 23 June 2007

A work in Progress
Since this privately funded project, a commo truck for use by the Texas State Guard, was started in 2002, it has evolved as time and money permits. It is fully operational and ready to go on a mission for up to 72 hours with self contained Diesel generator and power.

partial schematic of additions
voltage metering circuit (mod to DC power supplies)

"Field Day" with the Irving Amateur Radio Club

Four 92AH 12V Hawker-SBS AGM batteries. They are connected in series for 24V and arranged in two separate banks that are independently switched to the 12/24 bus. One could argue that the only 24V items are the 35-watt military RT246 and RT524 30-75MHz FM radios and a 24V work lamp. But, it's a military vehicle and it would be 'wrong' not to have 24V power..

Looking forward along the curb (right/starboard) side. The power panel allows independednt monitoring of two 120VAC power sources as well as the 24V supply. Nearly every "switch" is an AC or DC electromagnetic circuit breaker.

The rear hatch. The GRM shelter was last used by the Marine Corps as a shop for for repairing electronics equipment. After repaining, I applied an appropriate sticker in honor of their service.

On the street side (left/port) the original cabinets in gray remain, and a 19" rack cabinet about 48" tall was installed to house a 100W UHF business repeater. The repeater is coming out, and the rack can find another use.

forward of the repeater cabinet, the tabletop is stacked with bedroll, cot, two 40FT antenna mast systems, multiple mag-mount antennas, and other goodies.

The exhaust fan is composed of two 24VDC fans mechanically in series. The voltage can be set to 24V or 12V for hi/lo speed. Good for when the air is foul or if the smoking lamp is lit. The 8000BTU air conditioner above the fan keeps up with things until it hits near 100 degrees. Then a larger system is energized.

The emergency light charges from 120VAC and comes on when the power goes off. A small switch was added to allow disconnection of the battery in the light so that the thing won't go completely dry and be ruined during an unattended power failure. As long as the battery is charged with the switch on for a couple days once or twice a year, it is fine. Below the light is the main DC bus circuit breaker panel.

Two 12VDC power supplies were modified and put in series to charge and operate the 12/24VDC system. Each one is independently adjustable and isolated by diodes so that the batteries cannot self-discharge. In case the AC power is out, the DC power of the bank of batteries attached to the DC bus can be measured by throwing the toggle switches and reading the battery voltages directly.

This is the evaporator unit of the secondary air conditioner. The system is made from parts and is intended to reduce the temperature and humidity of the air flowing through the coil as much as possible, rather than blowing alot of air. This decision was made since the repeated opening and closing of the door in hot weather raises the humidity more quickly than the temperature and it is desired to prevent interior metal surfaces from "sweating" since there is alot of sensitive electronic equipment.

Common and special tools are stowed under the 'desktop' surface at the fore end. Tools range from those used to work on the large truck to those used to repair and set up delicate electronic equipment, including a temperature controlled soldering station, impedance analyzer, and oscilloscope.

The main operator position includes an Icom IC706, Alinco DR-135, Alinco DR-435, the antenna matching unit for the Icom, and a CB radio. The CB radiomis tied into the VIC-4 intercom in the truck. The VIC-4 allows a user at any station to select and transmit on one of four radios while monitoring the others and using the intercom. The VIC-1 is more common, allowing two RT's and a receiver and intercom.

Better image of the radio sets. The microphones stow behind the radios on the shelf. The antenna switch is a little cheezy, but that is temporary.

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