Lots of checking of antennas here. Easiest way to check the antenna is to
put a pulley on the tower and then haul the antenna up to at least 10 feet
or so for 10-20 meters. This will give you a rough idea that nothing
major is screwed up. The SWR on most antennas will be a little low in freq at
this height but it should work.
But like John says, for a really accurate measure 30 ft is the way to go.
Bill K4XS...soon to begin building on KH6
In a message dated 9/28/2015 11:16:02 A.M. Coordinated Universal Tim,
john@kk9a.com writes:
It is a waste of time checking an antenna near the ground. About the only
thing you can determine is if the coax is connected. You need to pull it
up at least 30' high.
John KK9A
To: <TowerTalk@contesting.com>
Subject: [TowerTalk] Expected VSWR of antenna near the ground
From: "Doug Ronald" <doug@dougronald.com>
Date: Fri, 25 Sep 2015 18:16:17 -0700
I have assembled my 19 element LPDA with the front 12 elements about 3 feet
off the ground and parallel to the ground. The back elements are laying on
the ground, but electrically connected in the usual LPDA way. Today, as a
check before I erect it, I swept with a VNA, the antenna from 1 MHz through
32 MHz. The VSWR is horrible! It has peaks and deep dips at the low end,
and
then at 14 MHz or so, rises to over 5:1 and stays there. Now I didn't
expect even 2:1 over the range, but I expected the VSWR on the high end to
be at least reasonable, because the front shorter elements are off the
ground.
Anyone care to weigh in with an opinion? I hoping an expert says this is
perfectly normal for an antenna just a few feet off the ground. If not, I'm
kind 'a stuck as I have checked all the connections with an ohm meter, and
they are all okay.
Thanks,
W6DSR
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