I use a crossover with two Top Ten switches as per their application notes.
No problems so far.
[mailto:email@example.com] On Behalf Of Tom Rauch
Sent: Wednesday, January 05, 2005 1:28 PM
To: Jim Lux; RCARIELLO; Towertalk
Subject: Re: [TowerTalk] Help need Vacuum Relay Isolation 1.8 to 30 MHz
> Did you happen to measure the impedance characteristics of
the cross talk?
There are multiple causes at work including ground loops in
a PC board. It seems many switches have more problems with
ground loops and lead dress than with relay capacitance.
> Here's a scenario..
> If you had several fairly directional antennas, pointed
> directions, with good isolation (say they were on opposite
sides of a hill..
> a situation mentioned on the list recently), and you
wanted to hook a
> transceiver to one antenna, and use a receiver to monitor
the other at the
> same time, on the same band, and then be able to switch
> (Hey, maybe you're looking for your own signal after going
all the way
> around the world?)
Why wouldn't someone switch radios ahead of the amplifier in
a rare situation like that? It would be pretty foolish to
have two amplifiers on a single band. When we duplex on 160,
each radio shares a single common amplifier. The crossover
is done before the amps.
> I don't recall exactly what the original post was (it's on
> computer), but wasn't he switching multiple antennas to
either of two
> radios? Antenna 1 goes to radio A or B, Antenna 2 goes to
Radio A or B,
> etc. Antenna to the moving arm, radio A on one relay
contact, radio B on
> the other relay contact.
That would be like pointing a loaded gun at your radio! I
hope no one would be foolish enough to build a crossover
switch with multiple SPDT relays!!!
It should be relay armature to relay armature. Antennas to
either one stationary pole or the other pole of one relay,
and rigs to either one stationary pole or the other of the
There is absolutely no way to do a safe crossover with two
SPDT relays. It is a recipe for disaster.
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
TowerTalk mailing list
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
TowerTalk mailing list