[Elecraft] RF Chokes (renamed)

[Geoffrey Mackenzie-Kennedy]

Jack Smith wrote on Thursday, July 31, 2008 at 7:08 PM:

> There's also a possible concern with the chokes generating harmonics if 
> driven into or close to magnetic saturation.

Jack's warning is one good reason why chokes wound on ferrite cores, or 
powdered iron cores, for use as 'static bleeders' have to be designed very 
carefully if IMD generated by the chokes themselves is not to become a 
problem when they are subjected to strong signals e.g. AM broadcast as one 
example. At low values of magnetic flux within the core the level of IMD 
products might be acceptable, but not so at high values of flux. Without 
going into detail two good guidelines are to use as many turns as possible 
for the required inductance which requires lower values of core mu, and use 
a large diameter core not simply stack small cores.

A similar situation exists in a particular receiver's front end L-C filters 
where T94-10 cores are used to maintain an IMDDR3 of 120db at 7 MHz.

IMHO non inductive resistors are still the best bet for draining static.

My apology if this has been said already, I have been away.

73,
Geoff
GM4ESD