20dB F/B would be incredible for a short 2el 40m beam AT the resonant
frequency. You should have adjusted your beam for a higher frequency if
you mostly use the phone band.
John KK9A
[TowerTalk] F12 Delta 240 performance observation
from [SPWoo] [Permanent Link][Original]
To: "towertalk@contesting.com" <towertalk@contesting.com>
Subject: [TowerTalk] F12 Delta 240 performance observation
I have a D240 and I haven't
used it much since I put it up this past spring. Tonight I decided to
run some performance tests. I found a DX station and I turned the
attenuator
on such that that my S-meter was reading S9 when the beam is pointed at
him.
When I turned the beam 90 degrees away I saw an S7 which is 12 db less
than the
maximum signal strength. When the beam was turned 180 degrees away I
saw an S9
which is the same signal strength
as when the beam was pointed directly at him. I'm a little confused
about
this. This is
supposed to be a yagi and not a rotary dipole! The listed spec. for F/B
ratio
is 20db at its peak. I do know that F/B is not constant across the band
for a
yagi. What kind of front to
back and side rejection ratios should I expect to see on this particular
antenna? I haven't asked Mark at F12 about this. I don't want to waste
his
time until I have more info. Perhaps I'm missing something on the test
or that
I made an error in my antenna assembly. Your help on this is greatly
appreciated. 73.
Jonathan Woo W6GX
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