I believe that capacitor might be to help prevent a loud click in the
receiver when the direction is switched. When the voltage is suddenly
removed from a relay coil, there can be quite a pulse from back EMF as the
magnetic field on the coil collapses. Maybe it is to control the rate of
collapse, thus preventing a big RF spike.
On Fri, Mar 23, 2012 at 11:40 AM, Herb Schoenbohm <herbs@vitelcom.net>wrote:
> I would avoid any attempts to do relay switching by supplying voltage down
> a coax cable but rather use two coax runs.
I do it both ways here. And both have proven very reliable, after taking
certain preventative measures (both electrical and mechanical).
> Another disadvantage of having a blocking cap in the signal line is that
> you can not determine the coax run continuity through the windings of
> toroid back to the shack with a common VOM.
>
The way I check coax continuity --and whether the relay is operating-- is
with a super bright LED than can be seen from the house at night, several
hundred feet away. It's connected to a contact on the relay.
It could also be done by applying the normal switching voltage to the coax
in series with a milliammeter (just use your VOM) and measuring the current
at the shack; if there's no (or very low or very high) current, then you
have a problem.
I gar-run-tee you that no ants will get inside the remote control boxes
here. And with those completely sealed enclosures, no water has entered,
and nothing inside has deteriorated after several years outdoors, either.
I think DXE would have done their customers a favor by putting that little
DIP relay in a good socket and using GDTs, etc. to give the relay and
transformers a better chance of surviving at least some surges induced in
the antenna by nearby lightning strikes. But that's just my opinion; maybe
the spark gaps that I've heard they have built into the circuit board work
better than I think.
If anyone wants to build their own reliable remote Beverage switch, take a
look at the schematics, photos, etc. of the two different types at
http://www.w0btu.com/Beverage_antennas.html.
73, Mike
www.w0btu.com
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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