[TowerTalk] AC operated relays for ant switching

[dan hearn]

Good point Tom. Even though the 1N4000 series diodes are inefficient at r.f.
frequencies, we have long wire leads to them which act as antennas. It would be
good practice to bypass them and I will do so. I might mention that a friend in
Dallas had a TVI problem caused by an oxided joint where he connected a bare
copper ground wire to a galvanized tower leg. That "poor rectifier" caused
plenty of trouble. Thanks, Dan, N5AR

w8ji.tom wrote:

> Hi Dan,
>
> Great suggestion.....I would also worry about 120 vac running everywhere,
> especially outside around the antenna wiring.
>
> > I have a home built ant sw using relays w 110 a.c. coils. They work fine
> and do
> > not overheat with 24 v.d.c. on the coils. This, of course is much safer
> than
> > using the 110 a.c.
>
>  I use  a back connected diode across each coil to keep the
> > inductive h.v. spike on disconnect from damaging the selector sw. Haven't
> found
> > bypassing necessary if the diodes are slow speed power types like 1N4001
> > series.
>
> 1N4000 series diodes may not be high speed diodes, but they still rectify
> RF pretty well Dan. I use them on a regular basis for RF clamps to protect
> HF receivers! They are used in the all the Ameritron amps as meter clamps,
> and rectify RF well enough to generate harmonics (and change meter
> readings) when they aren't bypassed.
>
> I'd bypass them.
>
> 73 Tom




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