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I've just built a coaxial half wave dipole for 6m to talk to Bob85. First mistake: My upper element is 143cm long and so is the coaxial lower element, my isolation pole is also 143cm long which meant my choke overlapped the isolation pole and the mast and yes you guessed it - the choke coupled with the mast and detuned it. Second problem, any rain on the choke and it sends the swr to hell, probably lowering the impedance so that I start radiating on the coax underneath the choke and the mast although I didn't notice CMC in the shack, chances are they were there though. I've now stopped the choke coupling with the mast via a rubber bung and i've taped the choke to hell and back to keep water from it. So much so it lowered the impedance of the choke slightly and I had to retune the antenna. All in all they work and that's it. Do anything to the choke and lower coax leg including coughing on it and it changes the resonant frequency. Not a fan I'm afraid.

<blockquote data-quote="nav2010" data-source="post: 750424" data-attributes="member: 14757"><p>I&#039;ve just built a coaxial half wave dipole for 6m to talk to Bob85. First mistake: My upper element is 143cm long and so is the coaxial lower element, my isolation pole is also 143cm long which meant my choke overlapped the isolation pole and the mast and yes you guessed it - the choke coupled with the mast and detuned it. Second problem, any rain on the choke and it sends the swr to hell,&nbsp; probably lowering the impedance so that I start radiating on the coax underneath the choke and the mast although I didn&#039;t notice CMC in the shack, chances are they were there though. I&#039;ve now stopped the choke coupling with the mast via a rubber bung and i&#039;ve taped the choke to hell and back to keep water from it. So much so it lowered the impedance of the choke slightly and I had to retune the antenna. All in all they work and that&#039;s it. Do anything to the choke and lower coax leg including coughing on it and it changes the resonant frequency. Not a fan I&#039;m afraid.</p></blockquote><p></p>

[QUOTE="nav2010, post: 750424, member: 14757"] I've just built a coaxial half wave dipole for 6m to talk to Bob85. First mistake: My upper element is 143cm long and so is the coaxial lower element, my isolation pole is also 143cm long which meant my choke overlapped the isolation pole and the mast and yes you guessed it - the choke coupled with the mast and detuned it. Second problem, any rain on the choke and it sends the swr to hell, probably lowering the impedance so that I start radiating on the coax underneath the choke and the mast although I didn't notice CMC in the shack, chances are they were there though. I've now stopped the choke coupling with the mast via a rubber bung and i've taped the choke to hell and back to keep water from it. So much so it lowered the impedance of the choke slightly and I had to retune the antenna. All in all they work and that's it. Do anything to the choke and lower coax leg including coughing on it and it changes the resonant frequency. Not a fan I'm afraid. [/QUOTE]

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