Topband: Relay switching at the base on antenna

[Richard (Rick) Karlquist]

There is nothing simple about this, because you need to
avoid hot switching.  This means that you need to start
with the rig signal that is intended for use with QSK
linears.  This signal will change to the transmit
state 10 ms before the transmitter actually starts
putting out RF.  The name of this signal will vary
depending on the rig, and the "PTT" signal may or may
not be the correct one.  Additionally, in some rigs
you may need to put a switch in the QSK position
(such as the FT1000).

Once you have a 10 ms head start, you need a relay
that will close in less than 10 ms.  If necessary,
you can use speed up circuits that put a temporary
overvoltage on the coil of the relay.  This requires
that the relay is energized on TX and non-energized
on RX, rather than vice versa.

In keeping with the word "simple":  a piece of hook
up wire running to the base of the antenna is much
simpler than trying to send DC on the coax, depending
on how hard it would be to install this wire.  You
can still use the shield of the coax as the return
connection.

Rick N6RK

On 9/23/2017 5:39 AM, MR TREVOR DUNNE wrote:
> Hi All
> 
> Can Anyone tell me a simple way to switch a 12v relay at the base of an antenna using the rigs ptt as the trigger??
> 
> Thanks
> Trevor
> EI2GLB
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