Topband: Detuning TX Antenna

[Chortek, Robert L]

Hi Tom,

The switchbox is a homemade relay box located at the base of the vertical about 100 feet from my shack.  One relay adds in a loading coil at the base of the 60'  vertical antenna for 160 meters.  When the shack switch is turned off, the loading coil is disconnected and the antenna is then tuned for 80 meters - the default position.  I don't need to detune on 80 since the re-radiated noise on that band is minimal.  Another relay  can add/subtract  additional inductance to move the resonant point around somewhat on 160 and from 80 to 75.

I built an "on/off" switch on my desk powered by a 12 v power supply that controls the power to the relays at the base of the antenna.  

I had planned to add another  12v relay which would just control the voltage from the shack powers supply and it would be controlled by the TVSU.  The TVSU would be used to control a relay that would simply turn the power from the shack supply to the desk on/off switch off and on.   My plan is to wire the new 12v relay so when I hit the key, the TVSU will result (ultimately) in the relay at the base of the antenna controlling the 160 meter loading coil being activated -adding loading coil so the antenna would be resonant on 160 meters.  When I release the key, the loading coil would be disconnected and the antenna detuned (back to the 75/80 default position).  The TVSU would make sure the timing is correct 

I hope that makes sense.

Thanks for your input. 

73,

Bob/AA6VB

-----Original Message-----
From: Tom W8JI [mailto:w8ji at w8ji.com] 
Sent: Sunday, December 08, 2013 10:24 AM
To: Chortek, Robert L; topband at contesting.com
Subject: Re: Topband: Detuning TX Antenna

> I am finally getting around to detuning my 160/80 meter vertical on 
> receive and plan to use a simple 12v relay to turn off the power to 
> the antenna switch and the DXE Time Variable Sequencer to make sure 
> the on/off timing is correct.
>
> Before I go down that road, does anyone have any suggestions?
>

What is your antenna switch, does it open or short, how far from the antenna is it, and how are you disabling it (how are you removing power)?