The need to disconnect the feedline shield is to block common mode signals. A K9AY approved **EXCELLENT** common mode block (not a regular "balun" with likely awful blocking on 160m), or (GASP) an isolation transformer will take care.
In the case quoted, with the coax center contductor opened, the stinky-on-160-blocking "balun" is how the noise gets in. Further since Pete saw a 4 S unit drop by simply disconnecting the TX wire, it's likely that his common-mode provision, even if not intended as such, would appear to be satisfactory, and therefore a double pole relay (lot more expensive) is not called for. 73, Guy K2AV On Sun, Dec 8, 2019 at 7:30 AM 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