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Old January 19th 04, 09:34 PM
H. Adam Stevens, NQ5H
 
Posts: n/a
Default mobile antenna impedance comparison

QST
It's been a while since I posted all that bazooka data that made me stick to
dipoles, so here goes:
I've been using Hustlers mobile for almost 40 years and find them adequate;
The mast I bought in 1970 only recently failed.
I'm reworking my HF mobile installation around a TS-480HX and decided to
graduate to a screwdriver. I bought a Tarheel 200.
I prefer to operate a mobile antenna at it's resonant frequency and match to
the impedance of the transmission line with a transformer.
So here I present the resonant feedpoint impedances of a Hustler (small
resonators), the Tarheel 200 screwdriver and a 103" whip on a bug catcher on
a 54" Hustler base. All antennas on the same ball mount. Measurements by
MFJ. "Resonant" implies X=0.

band Hustler Screwdriver 103"/BugCatcher/54"
80 21 ohms 9 ohms 23 ohms
40 25 11 na
20 30 30
10 40 32

I really thought the huge bug catcher would do better.
The screwdriver shows encouraging results for signal improvement over the
others on 80 and 40.
Seems the diameter of that bottom conductor on the screwdriver makes a big
difference at the lower frequencies.
Since the TS-480HX has two antenna jacks, I think an additional small
screwdriver is in order; One for 80-20; One for 20-6.
73
H.
NQ5H