As you figured out, there is no perfect height. I would avoid going too
high where you create nulls at critical angles. My question is why do you
want to use a Log Periodic? I have never modeled one but they look to be
nothing more than multiple dipoles and they can have common mode current
if the coax is not properly routed around the hot boom. I used a small LP
once from the Caribbean and never felt loud.
John KK9A
To: <towertalk@contesting.com>
Subject: [TowerTalk] LPDA optimal height
From: "Jeff AC0C" <keepwalking188@ac0c.com>
Date: Mon, 13 Feb 2017 18:06:18 -0600
I’m considering putting up an LPDA this summer to augment the existing stuff.
The LPDA would serve two purposes:
1. 30m/17m/12m DX chasing. I suppose that really means 30/17 as I can’t
remember the last really solid 12m opening...
2. Fixed-on-SA for 20/15/10m when contesting.
The problem is the usual tools for helping on height (HFTA) are more or less
band specific so what is the best height on (for example 20m into SA) is not
really a great height for another equally important (e.g. 30m DX into eastern
side of EU). In playing around with HFTA clearly each height seems to
provide
some benefit over another. Higher band and higher height gives more nulls
but
better low angle performance.
I figured that something around 80-100’ overall but would greatly appreciate
any suggestions...
73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie
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