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 <ranchoro...@gmail.com> 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. 73 Rob K5UJ _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector