Topband: Hi Z amplifiers for 160m

[Ralph Matheny]

Lankford's stuff works great.

I have used his antenna which does NOT use
a preamp.....it's only suitable for situations
where match to the feedline isn't critical, but
it sure is great to not have any preamp outside.

de K8RYU


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From: Topband <topband-bounces+mathenyr=marietta.edu at contesting.com> on behalf of Mikek <amdx at knology.net>
Sent: Thursday, March 12, 2020 7:29 PM
To: topband at contesting.com <topband at contesting.com>
Subject: Topband: Hi Z amplifiers for 160m

  I'll stick my neck out and suggest Dallas Lankford's '2 FET amp'.
  He designed it for phased loop antennas for the MW band.
  I believe it will work to at least to 9 MHz and maybe to 30 MHz.
The specs High input Z, ~100 ohm output Z. He lists input intercepts:
IIP2 = ~ +88dbm and IIP3 = ~+41dbm in the MW band.
  The webpage has some noise measurements on pages 3, 4, and 5 that were
over my head.


   This page has more than just his amp but enough so you can understand it.
  If anyone has an interest, I have some more files in my computer.


> https://www.okdxf.eu/lankford/Hi%20Z%20PPL%20Loop%20And%20Flag%20Arrays.pdf

I have a plan to put a matching transformer and a Hi Z amp on my antenna
with relay switching,
so I can do a real A, B, comparison. If you have any advice on
implementing that or advice about
common mode filtering, I'm listening. Better relay suggestions would be
appreciated.

                                                  Mikek KF4ITA
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