Your feedline is about 350 feet. That is (with RG213 -velocity 0,66-) close to 1 wavelength. With 1 wavelength feedline, the TX antenna is floating when the feedline is open in the shack.
I'm sorry to say that , but the concept is wrong, the TX antenna resonance as structure has nothing to do with the impedance. Floating the element makes it 1/4 element, keeping it connect it works like a 1/2 wave resonant antenna. I presemted some solutions on my Webnair at wwwrof, still available and you can download the slides with extra information. Like PY2XB inverted V when disconnected from the feed line drops the noise 2 S units on the RX antenna. Changing the impedance you can notice a change in the noise but only few dbs. JC N4IS _________________ Topband Reflector Archives - http://www.contesting.com/_topband