[TowerTalk] Relays for antenna switching?

[Rick]

Dan,

I have been using remote ant relays for over 15 years; that way I only run
one coax into the house (also switch ant. rotors with relays).  For years I
used  ones made by Unadilla and they were called "Inline Coaxial Relays".
They were carried by Radioware out in Westford, MA.

After moving to a new QTH 5 years ago, I needed some more and after calling
Radioware found out they were no longer in production; but the salesman said
he thought they might be available at a later date (i.e. if they went back
into production).  Their tele number is 1 -800-950-WARE  (9273).

Needing something right away, I went down to what is now Radio Shack.Com and
bought some small 12V. SPST relays and mounted them in waterproof metal
boxes that I also bought their (AN-1302,  1.18"h, 2.56"w, 4.53"l).   As you
can tell, the relays are fairly small to fit in the box.  I didn't see the
ones I used in their catalog, but I think they were around 10 Amp and were
about 1" long and 1'2" or so thick.   Cut holes out for female chassie mount
PL-259 connectors and where necessary, a grommet to bring out the control
wire.   A couple I made also are switched by DC on the Coax, so a DC control
wire is not needed.   Just need a RF choke and a capacitor (and a diode if
you care about if the relay closes on + or -  DC).   Heathkit used to make
an  ant switch (HD-1481).  That unit was capable of swithing 4 ants remotely
through the coax.  I found a schematic of that unit and patterned my system
after that (with some mods since I needed to switch 9 antennas from one
coax).

I think I made 3 or 4 for my self and 3 for a buddy here in Denver (K7XM) to
switch 5 antennas.     I have been using them for over 5 years at my QTH and
K7XM has been using them for over 2 now.    I don't notice any appreciable
SWR change with them in or out of line; don't know what the insertion loss
is (the Unidilla ones where 1/10 DB at HF).    I work everything I can here
(only ones I haven't heard are P5, YA, and 3Y/B); so I guess the ones I
built aren't to bad.   Both K7XM and my self run Alpha amps; so high power
is not a problem; just don't energize or de-energize the relay while
transmitting!

I don't think they would be the best choice at 2 Ghz; but below 30 Mhz, they
work fine

K8ZTT Dick
Franktown, CO





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