Topband: Detuning transmit antenna in receive

[W2XJ]

There is no single solution for detuning an antenna it depends on 
electrical length. For verticals a quarter wavelength or less it is 
common to have a contactor between the network and the radiating element 
and open the connection to float that element. This is the practice in 
commercial directional arrays where some tower are not used in a day or 
night mode.  This does not work well on taller towers and I do not know 
offhand how it would work with the T. It is easy enough to model in EZNEC.

On 6/16/12 3:02 PM, Shoppa, Tim wrote:
> OK, several folks came back and recommended detuning my transmit antenna in receive.
>
> Certainly any receive antenna I have is going to be in the shadow of my transmit antenna, a 130-foot flat-top about 85 feet up, fed against ground. (Really it's an 80 meter doublet fed with ladder line. I tie the ladder line together at the bottom and feed against ground.)
>
> Trying to figure out what "detune" is.
>
> I match the transmit antenna to 50 ohm coax with a L network at the bottom. If I want to detune, then I can.... open up the connection between the antenna and the L network at the bottom? Unhook the L or C in the L network? Short out the antenna where it comes into the L network? I could rig up a relay contact to do any of those.
>
> Tim N3QE
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>