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Re: [TowerTalk] HF LOG-PERIODIC ANTENNAS Comments Please

To: "Jim Lux" <>,"Larry Phipps" <>, <>
Subject: Re: [TowerTalk] HF LOG-PERIODIC ANTENNAS Comments Please
From: "Tom Rauch" <>
Reply-to: Tom Rauch <>
Date: Wed, 23 Jun 2004 10:46:14 -0400
List-post: <>
> Could you publish the model you used, including the length
and type of
> feedline you assumed?  I'm assuming that you're talking
about out-of -band
> mismatch loss?
>> I just ran a quick sweep of a 3el SteppIR model and the
loss in the feedline
>> alone due to mismatch is about 4dB at 1 mHz out and 10dB
at 5 mHz out. Add
>> to that the pattern loss and you're well over 10dB total
out-of-band loss
>> compared to a LPDA. That might not seem like much, but
10dB lower
> >interfering signal is roughly 20dB lower distortion
products. It all adds
>> up.

Why does a non-issue like that matter Jim?

Assuming you don't use a Knight Kit Star Roamer super-regen
who on earth would care if 1MHz signal level was even 50dB

This reminds me of silly things like claiming reducing
coaxial cable loss improves HF reception, or using a 5kHz
roofing filter to enhance CW reception. What a waste of
time. Virtually 100% of the problem is multiple strong
signals inside the passband of the roofing filter, and noise
floor is set by the noise environment around the antenna and
directivity. Selectivity or gain-bandwidth response of the
antenna is a non-issue. PERIOD.

Even very bad equipment like a TS-2000 or original R4C Drake
would never see any improvement from antenna selectivity.

73 Tom


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