This is really helpful. When I did the plot with the antenna on the ground,
all the dips below 5:1 VSWR were below 10 MHz. Then, after 10 MHz, the VSWR
saturated at the graph limits of 5:1. The complex impedance was all over the
map. I can see now with this information, that expected resonances were
definitely skewed to the low end, and the antenna is probably just fine.
I can't wait to get it to proper elevation!
-W6DSR
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
K7LXC--- via TowerTalk
Sent: Monday, September 28, 2015 1:15 PM
To: towertalk@contesting.com; john@kk9a.com
Subject: Re: [TowerTalk] Expected VSWR of antenna near the ground
> 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.
Yes, 30' high is a truer picture of the antenna resonance (which is
probably the number of greatest interest) but I ALWAYS put an antenna
analyzer on an antenna on the ground. What I'm looking for is that it looks
like an antenna; that is, it has a dip somewhere. No dip? Something's
wrong.
A dip shows that it acts like an antenna. Where is resonates is
typically below the band due to added ground capacity but that's what you'd
expect. So if it resonates below the band, it looks like an antenna and
resonates around where it should.
Actual resonance is shown when it's up in the air but it's never an
empty test to do it when it's on the ground.
Cheers,
Steve K7LXC
TOWER TECH
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