I have been experimenting for years with my 90
foot vertical with vacuum relays installed across
insulators at the 30 and 60 foot level. The
reliability problems with the relays are not related
to coil failures. The coil is the one thing I
have had no trouble with. However, the contacts
eventually fail for unknown reasons. BTW, we have
virtually no lightning in this area and there are
choke coils across the contacts to prevent static
build up. I have developed a motor driven wiper design that I
believe will be bulletproof, but I haven't installed
any of these switches yet.
To answer a couple of FAQ:
1. Why not just use a trap?
Answer: because on 75/80 meters, it won't cover the whole
band. The antenna will still "work", but the
upper portion will do some radiating (bad in an array).
Also, on 160 meters, you have an extra loading coil you may or may
not want. These drawbacks, in many cases, are not
a big deal, and I'm sure there are a number of happy
owners of trapped systems.
2. Why not just use the whole vertical on 80 meters?
Answer: a very good alternative. I've done that a
lot myself. You need to figure out how to match it,
of course. Some people have trouble with that, although
it's not rocket science. However, you can't use more than
1/4 wl if the vertical is part of an array.
Rick N6RK
> -----Original Message-----
> From: topband-bounces@contesting.com
> [mailto:topband-bounces@contesting.com]On Behalf Of Ken
> Sent: Sunday, July 18, 2004 10:41 AM
> To: Topband
> Subject: Topband: Switch for 160 meter antenna
>
>
> Hello,
>
> I am building a 160 meter vertical antenna, and perhaps incorporate a 80
> meter antenna within the same structure.
>
> I would like to switch out a top section of the of the antenna by
> means of a
> switch to break a connection leading to the rest of the above antenna
> circuit.
>
> I could easily do this with a relay, but I don't want to rely on any coil
> failures either due to voltages drop out or weakness of the coil of the
> relay.
>
> What I would like to fine if possible, a type of wiper or knife
> like switch
> that can be activated by a servo or similar type mechanical devise.
>
> Does anyone know of such a switch, and where to fine it?
>
> Thank you,
> Ken
> K3YI
>
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>
>
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