For those of you who might like to have an EZNEC 4+ file for both the 75/80
meter 8 wire cage antenna or the "True Wire Bazooka" I will send them to you
for your viewing pleasure if you send me your e-mail address.
I think you might find my results interesting.
The 75/80 meter Bazooka design is good for 400 Khz of bandwidth between the
2:1 points and is a 12" diameter cage at 67' high. When moved to 127' it
gets about 50 Khz wider and resonance moves up the band 100 Khz. Scaled for
40 Meters it never even gets close to that high an SWR across the band.
The Cage antenna is even MORE broad banded and is 65 Ohms resistive at
center band and only about 2.08/2.09 to 1 at the band edges even when
mounted only 65' in the air!
When mounted at 125' it is 37 ohms resistive at the center and about 2.13 at
the edges but it shifts up the band 150 Khz from the 65' height readings.
I might point out an old trick that works fairly well and that is to make
the antenna LONG and put a variable cap across the feed point to cancel out
the reactance as you move up the band. Use a gear motor to drive it or a
drive from an old floppy drive to tune it remotely and away you go.
OR, use a fixed cap and tune the antenna for CW band and have the cap
switched in with a relay powered up the feedline when you run phone. It
should keep the SWR down under 1.5:1 on each end with some tweaking of the
settings. Simple.
Let me know if this holds any interest for you and send me your e-mail
address and the files are yours to mess with.
Happy Signal Squirting.
Michael Baker K7DD
k7ddmjb@qwest.net
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