[TowerTalk] ground plane problem help needed

[Gene Smar]

 Jim WA7DUY:
     Are you attempting to get a ground-plane vertical operating as an elevated 1/4WL antenna using that base?  Or are you ground-mounting the 20M element using the base just to hold the element onto a ground stake?  Answering those questions will clarify for us what you're attempting to do.
     I have a similar 11M GP antenna from Radio Shack that I cut down by 11 inches (radials, too) to operate on 10M back in the late 70s.  I no longer use it but it was easily found in my garage today.  I just now measured the DC resistance of the base connections.  The SO-239 center pin to insulator set screw measures zero Ohms (as it should) on my el cheapo VOM; it measures about an Ohm between the SO-239 threads and the set screw.  So there is something there between the center conductor and the mounting base; not sure what it is, though.


73 deGene Smar  AD3F 
 
-----Original Message-----
From: Jim Pruitt <jpruitt67 at gmail.com>
To: towertalk at contesting.com
Sent: Mon, Aug 8, 2022 1:41 pm
Subject: Re: [TowerTalk] ground plane problem help needed

As near as I can tell these were not HyGain verticals.  The mount part
looks similar to them.  No, there is no choke anywhere.there is just the
black plastic insulator that the vertical part goes through at the top of
the bracket and another at bottom where the SO239 is located.

Thank you
Jim Pruitt
WA7DUY

On Mon, Aug 8, 2022, 4:32 AM Jim W7RY <jimw7ry at gmail.com> wrote:

> Is there a choke between the ground plane and the center conductor?
> An ohm meter will confirm.
> Hygain was famous for that.
>
> 73, Jim w7ry
>
> On Mon, Aug 8, 2022, 12:26 AM Jim Pruitt <jpruitt67 at gmail.com> wrote:
>
>> About 4 years ago I picked up 2 bottom sections of what I think were 11
>> meter ground planes.  The section looks like the bottom section for a
>> HyGain 18AVQ vertical or similar. The only difference is the mounting
>> flange has a plate that holds what looks like about ½" diameter ground
>> radials.  The issue I am having is that I used that mounting section to
>> make a 20 meter vertical.  Easy enough, right? WRONG.  I used mating
>> tubes to make the ¼ wave 20 meter vertical but it resonated at...ready
>> for this.... 39mhz!  Then I grabbed the second one and used it.  Now it
>> resonates at 13.5mhz but shortening the vertical does not bring the
>> frequency up.  I am wondering if perhaps someone (CBer maybe) ran way
>> too much power through them and broke down the dialectic of the plastic
>> (or whatever that is) insulator that isolates the vertical from the
>> mounting bracket and ground.  That is the only explanation I can come up
>> with as to why it is so far off.
>>
>> Does anyone have any suggestions as to how to fix the problem?
>>
>> Thank you.
>>
>> Jim Pruitt
>> WA7DUY
>> _______________________________________________
>>
>>
>>
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>
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