A Series-Inductance Impedance-Matching Device
Introducing : The Antoroid !
Not a strange mythical beast... but an idea that happened by accident and once I found it to work evaluated until I understood why. The idea is simple... when you have a physically short antenna for a given band, you need to do things to match it to the transmitter and resonate it. Traditional wisdom advises you put a capacitance across the feed point to match your transmitter, add a resonator coil and a stinger, and lengthen or shorten the stinger atop the coil until it's just right.
My method ADDS an INDUCTANCE in series with the antenna with the same effect of adding a capacitor across the feed point. This effect does not change resonance much, maybe 10% or so, that's all still controlled by the resonator coil and stinger. But the match is much closer to 51 ohms and works well on all coils from 17M up to 160.
A short mast, plus the antoroid, plus the resonator coil above it, and you get something that will delight your transmitter.
At left are the materials needed to build an antoroid, followed by a pix of an assembled unit before the bolt is cut, and finally a unit mounted on a mast and under a 20M coil. This approach lets me use a 36 inch mast on the trunk lid of a Mustang, and a standard Hustler resonator for 20M and still get an almost perfect match at the ALS500 output. I'll be posting the parts list and schematic soon !
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.
