[Elecraft] {OT} - Variation on use of a coaxial switch (stan levandowski)

[Charlie T, K3ICH]

Several companies (Bird, Transco) make what you describe.  It is a four
terminal coax relay called a "Transfer Switch" that for example, connects
any two antennas to any two radios, but never at the same time.  In other
words, radio A connects to antenna 1, and at the same time, radio B connects
to antenna 2.  Activating the switch ( either mechanical or electrically
activated) changes the condition for A to 2 and B to 1.  Most are good for a
kilowatt well up into the UHF ranges.   For HF, I made one using a heavy
DPDT relay.

73 Charlie k3ICH

-----Original Message-----
From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of
Richard Fjeld
Sent: Monday, January 02, 2017 1:13 AM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] {OT} - Variation on use of a coaxial switch (stan
levandowski)

Years ago, I built such a switch to prevent accidents should one radio
transmit when comparing two radios. It is basically an a/b switch such that
a radio became the active radio by switching the antenna to it, and
simultaneously switching the dummy load to the inactive radio. Neither radio
is without a load regardless of the switch position.

My switch is just a prototype using an aluminum project box.  I called MFJ
and suggested they build one. A couple guys got on the call with me, and not
long afterward, I saw a product advertised that seemed to be it.  It had
decent specs for isolation. I can't find it on their site now.  The only
thing that comes close to it might be the MFJ-1705, but they are describing
it differently and there is no schematic.

If this isn't the correct switch, It could easily be converted. The
important hardware is there.  I think I used a DPDT switch (I could check
mine).
It should have the small coax wired between the connections. I Don't
remember the nomenclature for that.

Dick, n0ce