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Old 22nd Sep 2020, 8:44 am   #2
trh01uk
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Join Date: Nov 2010
Location: Ross-on-Wye, Herefordshire, UK.
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Default Re: A 'Modern Vintage" 3.5MHz ATU.

Interesting bit of "cut and try" design there!

Just a thought about the possible flashover at the antenna side of the ATU. That would obviously depend on there being enough volts to produce the flashover, and in turn that would only occur if the resistive part of the impedance were to be high. You note the VNA told you the antenna is capacitive, but you don't mention what the resistive value was? Given that its not flashing over with a 100W its probably in the few hundred ohms region at most - or it might even be close to the 50 ohms your Tx needs to see - if the SWR is actually low on the Tx side of the ATU. Did you measure that?

Richard
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