General Forums > Technical Central

rf choke values

(1/1)

KB8OYR:
Is there a problem with substituting a larger value rf choke?  For instance:  if the ARRL handbook calls for a 30 micro henry choke for a class C amp on 30 meters and I wind a....say...200 micro henry one in it's stead, would it matter?

W7TFO:
The choke value is not only rated in uH, but also for a resonance point, usually relative to the distributed capacitance across it.

This is why you find some RF chokes having different-sized pies wound on it: to reduce the 'solenoid' effect of a single winding at particular frequencies.

If self-resonance occurs at a particular frequency, it will cease to perform the isolation function.  If it is handling power, such as in a plate circuit, it will probably burn and be damaged.

73DG

KB8OYR:
Thank you for the response.  My aim is use up some of my (non-spec) junk-box ferrite torroids as chokes so I can save my good ones (with specs) for design purposes.  I don't doubt your E.E. admonitions, but, as tired as I am at the end of my work day...   How about I just wind a couple of them up and try one.  If it burns the house down, I'll try the other.

W7TFO:
I'm such an old-school dinosaur I never even thought about a ferrite in the works...

With them, I'm of no use.

Best,

DG

KB8OYR:
Kind of you to say, DG and I'm your yeoman in this pursuit and keep looking for the answer by trial and error; usually the latter.  In the off chance I find something, I'll share it with the group. 

Navigation

[0] Message Index