Jim Meehan wrote:
> then I started wondering about using relays to simply switch out the
> various
> segments. If I used two-conductor speaker wire or something similar as
> the
> radiator, I think the same wire could also carry DC to operate the relays.
> I'd use SPDT normally-closed relays. For operation on 160, no DC is
> applied
> -- both relays are closed, and the entire length of the inverted L is
> active. For operation on 80, +12V is applied, opening the "far" relay,
> and tune.
> Am I missing anything obvious? I did a little Googling and didn't find
> any
> designs like this.
>> Jim Meehan, W6XE
> Oakland, CA
I have posted many times on this subject to this reflector.
I used a 40/80/160 vertical switched by relays for many years.
The relays were vacuum relays that never lasted more than a
year before needing replacement. When working, the vertical
was great, and the bandwidth was definitely better than with
traps. I recently decided to try modified open frame relays
as shown in my Hints and Kinks article in May 2009 QST. You
can definitely send DC through the lower relays to get to the
upper relays. I use a string of ten 1-meg carbon comp resistors
in series across the relays so that static voltage cannot build
up across the contacts when they are open. The relays should
be going into service late this year, so we will see how they
hold up.
Rick N6RK
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