[TowerTalk] ground plane problem help needed
Jim Pruitt
jpruitt67 at gmail.com
Tue Aug 9 03:46:48 EDT 2022
This is just the mounting base that I used. Then I used some aluminum
tubing I had (swaged so they fit into each other and clamped). This was
not a complete CB antenna. As I said, it was just the base for one and
I added the vertical element (above the short piece in the mounting
base). I use the mount to bolt it to a wooden post about 5ft off the
ground and run 1/4 wave radials (3 of them). Since both base mounting
sections were identical I was surprised at so much of a difference
between the 2. As I said, the first one I used was resonant at 39mhz
and this one is 13.5mhz. Resistance from the center contact (on this
second one) of the SO239 to ground is infinite (as it should be).
Resistance from center conductor of SO239 to vertical element is zero
(as it should be). That is why I suspect there is a problem with the
plastic used to insulate the vertical element from the mounting bracket.
Thank you.
Jim Pruitt
WA7DUY
On 8/8/2022 1:01 PM, Jim Rhodes wrote:
> The antenna I modified did happen to be made by HyGain, if I remember
> correctly. Someone gifted it to me when I lived in Lincoln when I was
> in school. It was a long sucker, 5/8 wave on 11 meters. First used
> it pretty much stock on 10 meters when first licensed, but decided
> there was more action on 20 so I shortened it to a 1/4 wave on 20.
> There was a transformer in the base to match the impedance of the 5/8
> wave, so the first thing I did was to remove it. Was only a round
> piece of pc board with a spiral etched on it about an inch in
> diameter. They were only built to handle less than 20 watts.
>
> On Mon, Aug 8, 2022 at 2:45 PM Jim W7RY <jimw7ry at gmail.com> wrote:
>
> As I said before. It's a choke.
>
> To provide a DC path to ground for static.
>
> 73, Jim. W7RY
>
> On Mon, Aug 8, 2022, 2:05 PM Gene Smar via TowerTalk <
> towertalk at contesting.com> wrote:
>
> > 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
> > >> _______________________________________________
> > >>
> > >>
> > >>
> > >> _______________________________________________
> > >> TowerTalk mailing list
> > >> TowerTalk at contesting.com
> > >> http://lists.contesting.com/mailman/listinfo/towertalk
> > >>
> > >
> > _______________________________________________
> >
> >
> >
> > _______________________________________________
> > TowerTalk mailing list
> > TowerTalk at contesting.com
> > http://lists.contesting.com/mailman/listinfo/towertalk
> > _______________________________________________
> >
> >
> >
> > _______________________________________________
> > TowerTalk mailing list
> > TowerTalk at contesting.com
> > http://lists.contesting.com/mailman/listinfo/towertalk
> >
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
>
>
> --
> Jim K0XU
> jim at rhodesend.net
More information about the TowerTalk
mailing list