[AMRadio] Antenna relays


Rob Atkinson ranchorobbo at gmail.com
Sat Jan 17 07:04:17 EST 2015


It depends on the frequency and type of feedline.  You can use open
frame relays with widely spaced contacts for open wire line.  EFJ made
such a relay (they are found in the KW Matchboxes).

I use a large 4PDT P&B relay inside an aluminum die cast  enclosure
for the low bands.  It all depends on how much impedance bump you can
tolerate.  If you use unbalanced coaxial line, preserving the geometry
of the line through the switch is probably only important at VHF.
Tube rigs don't care even up there I bet.  I paralleled 3 poles for RF
and used the fourth one to ground the rx line on transmit.  It will
handle a KW carrier with no problem.

What is important is that the relay you employ, is a relay with the RF
path consisting of non-ferrrous metals, copper, brass, aluminum,
silver.  Some steels vibrate with RF at the microscopic level and that
produces heat.

73

Rob
K5UJ

On Fri, Jan 16, 2015 at 7:54 PM, Steve Wender <tobiebw2 at newmexico.com> wrote:
> Hi All,
>
> What are your thoughts and experiences with antenna relays to switch an
> antenna from transmitters to receivers.  I have used Dow Key relays with
> pl259 connectors but I wonder if there are better things that can be made
> from regular relays in terms of signal attenuation etc.
>
> Thanks,
>
> Steve
> KC5WN


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