Today's Message Index:
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1. 01:05 AM - Re: Comm Antenna & SWR: Grounding Issue (Werner Schneider)
2. 08:48 AM - Re: Comm Antenna & SWR: Grounding Issue (kuffel@cyberport.net)
3. 09:48 AM - Shorai LiFePO4 (Jan de Jong)
Message 1
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| Subject: | Re: Comm Antenna & SWR: Grounding Issue |
Bob,
I would pull the foam on a 1/2 radius out, fill them with resin/filler
mix like the other cage holes, then drill them out to add a metal sleeve
over the screws, that one would touch the base of your antenna and the
groundplane (probably on two holes already enough), make sure the
sleeves a re a tad longer then the fiber ull thickness. Then mount the
antenna again (tarque screws)and use some rtv around the corner to seal.
That is what I did with my belly antenna and it works fine.
br Werner
On 31.01.2011 03:58, Bob Falstad wrote:
>
> I'll probably just have to pull the ground plane and re-do the mechanical mounting
again and hope I get a lower resistance.
>
> Would it make sense to get some conductive epoxy and bond a ground strap from
the antenna base to the ground plane? I know soldering copper to aluminum doesn't
work and corrodes almost immediately. I've seen some silver-filled epoxies
rated as low as 0.001 Ohm-cm but that stuff is expensive. Could I solder
a small ground strap to the antenna's metal base without damaging the antenna?
I've got room in the hole for the BNC connector to run a small ground strap
up from the antenna base to a ring terminal that I could clamp under one of the
mounting screws. Would conductive gel under the hardware help?
>
> Since I've got a glass skin between the antenna base and the washer stack that
leads to the ground plane, I didn't "brighten" the underside of the ground plane
-- just the top under each of the four machine screws. I'm thinking if I
brightened up both sides of the ground plane, there might be some improvement
because of the additional contact between the hardware stack, the machine screws
and the underside of the ground plane.
>
Message 2
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| Subject: | Re: Comm Antenna & SWR: Grounding Issue |
Bob,
Another issue you might want to keep in mind is the
characteristics of the surface under a belly mounted
antenna. Rebar in concrete or conductive soil near the tip
(as opposed to the base) of a whip antenna can screw up
performance until you are in the air.
A reverse example of this is up in Alaska (again) the
permafrost is very non-conductive. You could spread out an
HF antenna on the ground, tune it exactly to frequency and
raise it up 50 feet in the air with no change in
performance. Or more related to your possible situation,
Seattle's soggy soil is so conductive you can mount a
vertical antenna in the ground and have it perform well
without any of the normally required ground radial wires.
Tom Kuffel
Message 3
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Check out "Shorai".
New light weight Japanese LiFePO4 battery with quite enthousiastic
motorcyclist customers.
Works well enough at low temperatures.
Max. charging current 18A (no external shunts). Higher ratings coming.
Has a 5 pin plug that I suspect may give access to the 4 cells.
For our use I might want to monitor max. cell voltage to see <4V or
interrupt charging.
Cheers,
Jan de Jong
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