[Amps] RF choke selection

[Richard]

>Hello all
>
>I've just re-subscribed to this list, so here's a question
>for everyone :-
>
>I'm trying to modify a surplus RF deck (an auto-tune
>2 - 30 MHz tube amp.) which has a 3-section plate choke.   
>One section is short-circuited by a vacuum switch, and 
>I guess that this was done above a certain frequency, 
>or maybe over a certain range(s) of frequencies to avoid
>choke self-resonances.  I've had to remove all of the
>auto-tune control electronics (large parts of it were missing
>anyway) but I need to figure out which bands 80 - 10m need the
>extra choke inductance, and which don't.
>
>Maybe it's as simple as e.g. below 10MHz the vacuum switch is
>open, above 10MHz the vacuum switch is closed.  I've tried
>measuring self-resonances using my ancient Heathkit GD1-U
>GDO (that should jog a memory or two!) but I'm not convinced
>by this method.   

Measuring resonances without making a connection to the RFC is good..  A 
dip-meter does this - although coupling two coils that can not be put 
parallel to each other is a hurdle. 

>Any ideas how I can figure out the switching
>in/out of this plate RF choke section ?
>
Use a dipmeter to locate the lowest resonance and stay more than 6% away.

>I have not had time to measure the inductance of each section,
>but I will do this, which will help.
>
 inductance is not as critical as resonances. 

cheers, Chris     

-  R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K, 
www.vcnet.com/measures.  
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