[Amps] Tank circuit arcing

[John Becker]

> Date: Wed, 09 Jan 2008 13:12:41 -0500
> From: Scott McGrath <mcgrath at fas.harvard.edu>
> Subject: Re: [Amps] Tank circuit arcing
>
> The insulating coatings suggested are not going to solve the primary 
> issue which is high RF voltages developed in the tank circuit.
>   
Why not?
> since you are running out of inductance that suggests that the amp's 
> tank is not designed to support 12m operation and since 12M was
> not even allocated when the amp was built any 12M operation is a 
> bonus.
>   
Actually, the Henry 3K is designed for continuous coverage. In the "10M" 
position, it will tune from 24-30 MHz. I'm not running out of inductance 
on 12M, as the rotary inductor is set for more inductance on 12M than on 
10M.
> The arcing is eventually going to blow expensive components like 
> bandswitches, tubes and caps
>
>   
What I'm experiencing on 12M is a frying or sizzling sound, not a sharp 
sparking sound. Perhaps the word "arcing" wasn't the best term to use to 
describe the situation.

Before I try the insulating coatings, I'm going to see if I can slip a 
slit piece of teflon tubing over the end of the rotary inductor at the 
point where I think this is happening.

73,

John, K9MM