[TowerTalk] Ground Mounted Vertical Question

[Gene Smar]

Dick:

     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.)


73 de
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

Hi Guys,
 
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 
radials.
 
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!
 
73,
Dick- K9OM  



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