[Elecraft] KPA500 mobile?

[Ron D'Eau Claire]

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