Topband: K9ay loop not performing

Raoul Coetzee raoulcoetzee at
Mon Dec 9 01:29:11 EST 2019

 I use a a relay to disconnect to the vertical portion just above the bottom matching coil, keeping all else connected.
 I do not understand why  the shield should be disconnected ? 
If it carries RF back it could be decoupled by ground rods to shield or chokes.Bu if he top section is open circuit, there would not be any signal to carry back in the first place.
Raoul ZS1C

    On Sunday, December 8, 2019, 2:30:00 PM GMT+2, Rob Atkinson <ranchorobbo at> wrote:  
 If you open the tx antenna feedline for rx, from my experience, you
need to completely open the entire feedline, namely the coaxial cable
shield as well as the center conductor.  coaxial relays that maintain
conductivity of the shield when N.O. won't detune/isolate the tx
antenna.  I use a pair of open frame relays for this.  Fortunately on
1800 kc the Z bump is almost nonexistent.  What will govern your
choice of relay is tx power and tx time, and whether or not you
require QSK.  I do not, but if you do, you may have to consider
something like multiple paralleled reed relays tor speed and power, or
vacuum relays.

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