Top-Fed / Top-Loaded / Grounded-Mast
HF Antenna for 500 Watt Mobile
It starts with how the base is wired. The ball mount is GROUNDED to the car frame ( as is the amplifier and transceiver using copper and aluminum tape, solid copper ground wire, stranded copper ground wire, and very thick ground jumpers almost everywhere. One benefit of going to all this trouble is that I have absolutely no trouble with any of the car's systems - not cruise control, radio, EEC, etc. Nothing strange happens no matter what band I'm on ( and that's 70cM through 160M ).
Here's a couple of the masts, I use three in all. The short one is for 10 and 12M, the medium one is for 15 and 17 and sometimes 20M using the antoroid, while the long one is for 20M without antoroid, 40, 80 and 160. There's another really long ( 72" ) mast I use that mounts on a bracket at the bumper level. That's used for 20M on long trips. Don't think this works ? On Sunday, Mar 3, I worked EA8BH in the Canary Islands from my driveway at home ! And busted a pile up doing it too !!!
This is the other end of the mast - the business end ! The coax shield goes to the metal of the ( grounded ) mast while the center conductor goes to the base of the resonator coil. When tape is over everything it looks like any other base driven top loaded antenna mast. But it's not the same - it's actually a top driven top loaded extension of the car body and resembles an inverted lazy L. I suspect the antenna behaves more like a Lazy 'L' with the feed point and loading coil at the short end of the L.
Schematics of the antenna and the Half Gallon Mobile HF Station
Below is the same type of grounded mast mount mentioned above, but this one is at the base of the bumper on a bracket that ties to the frame of the car.
General information ...
Absolutely everything here is copyrighted in one form or another... but free for anyone to use for non-commercial purposes supporting Amateur Radio and related hobbies. If you see something here that's useful feel free to copy it and show others - all I ask is you acknowledge the source.
Copyright © 2002 - William E. Warren