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Ralph Mowery · October 14th 18, 10:13 PM posted to uk.radio.amateur,rec.radio.amateur.antenna

In article ,
says...

I installed a few radios in White Freightliner tractors in the 1960's.
They were all positive ground 12V. I think they switch to negative
ground in about 1975. Many other older tractors were positive ground
but switched to negative ground in about 1954-56. I vaguely recall
conversion kits being sold at the time.

I've seen a few 24V electrical systems, but those were all in military
vehicles.

I have only ran FM ham rigs in a car. I used to ground the rig to the
frame and run the positive to a relay that comes on when the car is
started. Never had any alternator whine or problems. For about the
last 10 or more years I just plug into the lighter or accessory socket
in the car. My Toyota power on those sockets only come on when the car
is started.

You might want to put a voltmeter across the power connector going to
your radio and across the battery, and compare voltages in transmit.
Methinks you'll find a rather substantial voltage drop through the
cigarette igniter jack. Also, that connector was never designed to
handle a plug and jack connector arrangement. It's the only connector
that I know of that has a spring which pushed the plug OUT of the jack
and lacks a retention system.

Ok on the tractors being 12 volts. As I mentioned I did not know the
voltage but thought they were positive ground as the truck drivers kept
blowing the transceivers up when switching from the car to the tractor
and back again.

I did not put the voltmeter on the car,but a wattmeter shows the
transmitter is giving close to what it is suppose to put out. The
accessory jack is rated for 10 amps . This is for a transceiver that is
rated for 50 watts out.

I did melt out one of the inexpensive lighter plugs. It was made of
soft plastic instead of the hard type.