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Topband: EZNEC 5.0 + return loss and another question

Subject: Topband: EZNEC 5.0 + return loss and another question
From: Charles Yahrling <>
Date: Sat, 6 Dec 2014 21:09:46 +0800
List-post: <">>
Thanks for your explanations Charlie es Tom.  I guess return loss is the
opposite of what it sounded like to me. At any rate, you've explained why
it varies inversely with SWR.

Next question: in the manual the ALT IMPEDANCE explantion uses a 4:1
transformer example, which I get.  I've been toggling between RG213 50 ohm
and rg6/u 75 ohm to observe differences, reasoning that if I use a 75 ohm
feeder and get 2:0:1 or lower SWR  values, the 50 ohm "system" would start
(end) at the rig instead of the antenna feed point.  I noted that the SWR
bumped up a bit when I added a 120ft transmission line, which I would

Am I interpreting alt impedance feature and results correctly?

I don't have a single piece of 50 ohm  that long but have long pieces of
brand new CATV rg6/u from a hamfest jackpot.  In chapter six on
Transmission Lines in Low Band DXing the suggestion is to use a half-wave
section of 75 ohm to aid the match. I have enough rg6u and a 941E tuner if
needed to do this.

BTW this whole exercise is mostly intended as a lab session for me and a
way to get into top band quickly with a temporary antenna. I expected
before - and after looking at the FFT pattern have certainly confirmed -
that a flattop half wave dipole at 50 feet over rocky ground is not going
to work out as a DX antenna. But it might be good enough to allow me to NCS
a Tuesday night follow-on cw net after my regular net on 7.117, 0000z
Tuesday nights. Hope to be in business by Stew Perry contest.

73, chuck
de AB1VL
NAQCC #6799
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