Re: How to Isolate 2nd Transceiver in two Radio Base Station (WU6R / Mark)

Posted by Don Wilhelm on Jan 01, 2019; 3:14pm
URL: http://elecraft.85.s1.nabble.com/How-to-Isolate-2nd-Transceiver-in-two-Radio-Base-Station-WU6R-Mark-tp7647564p7647570.html

Mark,

The assumption that "there is a way to use both radios at the same time"
is the real base of the problem.

A lot depends on the power level you are running - the problem get worse
as the power is increased.

If you can reduce the pickup on the antenna used by the non-transmitting
radio, that will help a lot.  A horizontal antenna on one and a vertical
on the other radio may be sufficient at lower powers.  Physical
separation between the antennas will help as well, as well as good
common mode chokes on the feedline - use one at each end of the feedline
to choke off RF that is picked up on the non-transmit feedline.

If you do not have to listen to the non-transmit radio(s) during
transmitting, the problem becomes one of only protecting the other
radio(s) front end.  There are devices to accomplish that, or you could
simplify things by adding a relay that is activated to short the input
of the non-transmit radio when transmitting by the other radio.  That
relay (or relays) can be activated by the transmitting radio's amp
keying output.

As you can imagine, this can get complicated with only 2 radios, but you
also mentioned the inclusion of SDRplay, which may mean more than 2
receivers, and the situation becomes even more complex.

73,
Don W3FPR

On 1/1/2019 7:34 AM, Mark Wheeler via Elecraft wrote:

>
> I see lots shack photos with two transceiver setups, especially two
> Elecraft K3S radios; how do you isolate the 2nd transceiver or SDR
> receiver (SDR Play, for example) so that you do not damage one
> transceiver while transmitting with the other?  I am assuming there is a
> way to use both radios at the same time.
>
> Can I safely use an antenna switch to switch between multiple
> transceivers using one antenna, or will I risk damaging the
> non-transmitting radio on the other side of the antenna switch?

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