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Re: [TowerTalk] Sufficient ground or counterpoise for VHF/UHF antenna?

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Sufficient ground or counterpoise for VHF/UHF antenna?
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Fri, 24 Dec 2021 13:08:08 -0800
List-post: <mailto:towertalk@contesting.com>
On 12/24/2021 10:39 AM, Kevin Zembower via TowerTalk wrote:
Is this adequate for a ground plane or counterpoise?

Yes
I know it's not the
mass of a vehicle. The SWR is pretty good, I think. It goes from about
1.45:1 to 1.3:1 over the VHF band, and 2.5:1 to 1.3:1 in UHF (with a
consistent set of big fluctuations at 440 and 445MHz. What's that about?).

Either resonances in the sheet steel based on its dimensions, or conductive surrounding objects. SWR is NOT a measure of antenna performance, it only increases loss, and for the values you've measured, not by much. If the feedline isn't very long, I wouldn't worry about it. But I WOULD use coax bigger than RG58, which gets pretty lossy at VHF, even more at UHF. RG8X is a good choice.

73, Jim K9YC

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