I love to see people doing serious homebrew. Bravo!
I wonder if the SWR runaway at 150W could be due to the PVC pipe used as the insulator for the variable capacitor? PVC is quite lossy at RF. Perhaps when it gets hot it detunes the capacitor. It would be easy to check by simply feeling the cap to see if it gets warm.
Alan N1AL On 1/19/2021 5:39 PM, Andy Durbin wrote:
"although I saw a design not long ago that used two coaxial copper pipes with a PVC pipe as the insulator. The inside conductor was mounted to a long threaded rod moving it in and out of the outer conductor." Not my original idea but that's what I have on my loop (PEX insulator not PVC). Works fine up to 100 W on 30 m but has SWR runaway at 150 W. Capacitor is driven by a geared DC motor and is tuned from the shack. Home brew is far more fun than buying commercial. I'll post a link to a presentation if there is any interest. Andy, k3wyc ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
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