I have read of people tuning a Yagi beam antenna, (in this case a 6 Meter 3 element Yagi), with a variable air spaced capacitor.. Then removing the variable capacitor measuring the capacitance and fitting a fixed capacitor in it's place. The voltage is zero in the centre of the beam, current is maxium, with a 100 watts drive , voltage at the gamma match is what ??. I experimented with this and used a 50 volt ceramic capacitor, OOPS, problems. TOO low a voltage. WHAT is the current and voltage present at the capacitor??.When the capacitor was inspected, it had little black holes in it. Looked second hand. OK I needed a higher voltage capacitor. How high?? What type of capacitor ??. Ceramic, silver mica, multi layer ceramic, Door knob. IS it the current causing the problem. Variable capacitor has been refitted. NO further problems. DON'T touch, ok, agreed. My question is what type of capacitor could have been used, please
As a followup, yes, 70 Volts would explain the destroyed capacitor. Perhaps something in the 500 Volt or 1000 Volt range would been better. Mylar / polyester capacitors ??.(500 to 1000V).
