Q Dan, WA0YJE, asks, “I’m having trouble with a small HF antenna tuner. One of the knobs, and only one, becomes ‘hot’ when I operate at full output (100 W). My station is well grounded, so this is puzzling. Can you offer a suggestion?”
A If only one of the tuner knobs is biting you and not the tuner case, then I’d have to say the shaft insulator for that particular control is defective or installed incorrectly. Inside the tuner, you should see either a short section of insulated shaft (fiberglass, plastic, etc) or an insulating coupler between the knob shaft and the capacitor. It may need to be replaced.
From QST September 1999
