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UHF Egg Beater II



Howdy!

     I'm looking for some help on the UHF version of the Eggbeater II.
Jerry (K5OE) has been very helpful, but I am still having trouble, and
thought maybe someone has seen this before.  My test set consists of a Yaesu
FT470RH (FM Handheld) with a short coax driving a Welz SP-420 SWR bridge
followed by 50 feet of LMR-400 coax feeding the Egg Beater II.  I am also
using a very crude homebrew field strength meter.  The antenna is outdoors
at about 10 feet above the ground.   The nearest object is the house 40 feet
away, and the nearest metallic object is my daughter's swing set about 60
feet away.  The LMR-400 checks out just fine into the dummy load and into a
small vertical I have for UHF.  I am feeding the loops in parallel (I
haven't gotten to the phase line yet).  The little pigtails that feed the
loops are as short as physically possible (around 5/8 of an inch).

     The SWR response of the loops appears almost independent of the loop
size.  I have a low SWR around 433 - 434 MHz and again at 440 - 441 Mhz at
these two bands the reading is under 1.5 to 1 and my field strength meter
indicates the antenna is getting out.  Unfortunately, the from 435 - 438 Mhz
(where I want it work) the SWR is 4 to 1 or worse, and the field strength
reading is greatly reduced.  Increasing or decreasing the loop size seems to
have little or no effect until some massive change in size (more than 1.5
inches either smaller or larger) de-tunes the whole thing leaving no points
with a reasonable SWR, but the points where the SWR is best never shift in
frequency.

     The pattern holds with or without the reflectors, larger than normal
reflectors, smaller than normal reflectors, Antennas made with 8, 10, and 12
gage wire have all behaved the same.  I've got over 100 hours into this one
non-working antenna, and would happily accept any suggestion.

Thanks and 73,
Joe ka0yos

ka0yos@amsat.org
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