And then there's the car's electronics. Some
modern ones don't react well to high power RF. I
had one which didn't like 100 W -- though backing
off to 50 W made all things OK.
Phil W7OX
On 4/14/17 10:27 AM, Ron D'Eau Claire wrote:
One issue with mobile QRO is the antenna. While a mobile whip/loading coil
combo can be designed for high power, it becomes difficult to prevent corona
discharge from the end of the whip while transmitting at high power.
One fairly common solution decades ago was to mount a copper toilet tank float
on the end of the antenna. Of course the wind resistance then required guying
the whip. Since it was typically on the rear of the car, a nylon cord from the
mid-point to somewhere forward on the roof was common.
Another approach - back when car bodies were steel - was to extend the whip to
it could be bent over and tied to the front bumper, turning the car body and
whip into a small loop antenna.
Today, it might be hard to establish the necessary distance from the antenna
while sitting in the car to meet modern RF exposure limits, especially on 20
meters and up.
I never went QRO in my car, but had buddies who tinkered with it way back when vacuum tubes were
"king". Back then I lived in the land of the "California Kilowatt" (Southern
Calif.). They mounted outboard generators on their car engines to handle the power demand. Adding
filaments, etc., a kW mobile station might require 1.5 or 2 kW of d.c. power to run it. Got a
chuckle out of them when they'd key the mic to transmit while sitting at a stop light with the
engine at idle, and the sudden added power demand caused the engine to stall.
73, Ron AC7AC
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