[TowerTalk] Ground Mounted Vertical Question
ersmar at verizon.net
Thu Jul 10 18:02:59 EDT 2008
To paraphrase R.E.M., What's the frequency, Dick? The MFJ-259's are notoriously prone to misoperation in the presence of BCB transmitters. If this is a Topband antenna and you have a local AM BCB station, you might be seeing the effects of this energy overloading the -259.
If so, MFJ make a filter - MFJ-731, available for under $100 - that reduces this AM BCB interference to the -259 on 160, 80 and 40 M.
If your vertical is for other than 160, 80 or 40M - Son, you're on your own (to paraphrase the minister in Blazing Saddles.)
Gene Smar AD3F
From: RLVZ at aol.com
Date: 2008/07/10 Thu PM 07:39:16 EDT
To: towertalk at contesting.com
Subject: [TowerTalk] Ground Mounted Vertical Question
I'm installing a full-size ground mounted 1/4 wave vertical. I mounted the
vertical on a 5' pipe. The vertical is insulated from the mast pipe using a
base from an old Hustler 4BTV vertical. I will now get to work on the ground
Question: With the full-size ground mounted vertical connected only to the
5' mounting pipe, no radials, I thought I'd see what the SWR and impedance is.
I was expecting a low impedance of about 10 ohms. (poor ground = low
impedance = low performance)
However, using a MFJ-259B at the input of the antenna the impedance, at
resonant freq. is 100 ohms. (SWR over 2:1 as would be expected at 100 ohms).
I'll install the ground radials next... but the above doesn't seem right.
All thoughts appreciated!
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