A common mode choke (not really a balun) at a point of high SWR can heat up and as it does so everything drifts, making tuning impossible. Been there, done that using high power to a 160m Inverted-L that was close to resonant, but due to expediency was fed at a point of high SWR. A relayout of the antenna to lower the SWR fixed everything using the same choke (which luckily hadn't been permanently damaged).
73, Dave
From: Bill via Elecraft Sent: Tuesday, November 2, 2021 6:15 AM To: [email protected] Subject: [Elecraft] Problem Tuning K3 Jim, I assume your using a balun with your OFC antenna. I had a similar problem with my OCF that turned out to be the balun. It was fine under low power but would not tune under high power. Thanks, Bill - W0BBI
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