Topband: Relay switching at the base on antenna

[John Kaufmann]

I use the "Key Out" line of my K3S to drive the base of a homebrew
transistor switch that, in turn, drives a relay coil at the base of my
antenna. There is an isolation diode between the K3S keying line and the
switching transistor because I also use the same keying line to switch my
AL-1200 QSK amp.   I run full QSK with a Gigavac GH-1 vacuum relay as the
switching relay at the antenna.  I set the QSK delay in the K3S to 10 ms and
the GH-1 has a closure time of 6 ms.  It works fine.  I've never had an
issue with hot switching in full QSK.

73, John W1FV

-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of James
Wolf
Sent: Saturday, September 23, 2017 8:08 PM
To: 'Richard (Rick) Karlquist'; 'MR TREVOR DUNNE'; topband at contesting.com
Subject: Re: Topband: Relay switching at the base on antenna

Trevor,

I suspect you may be trying to detune the tower during receive, which I plan
on doing here as well.
Check your transceiver Amplifier Key Output line.  That line should close
about 10ms before any RF output from the radio occurs, for the very reason
Rick mentions below.

Any suggestions for the group on which relay to use for this?  I don't want
to give up my QSK.

Jim - KR9U
---------------------------
>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??


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