Ham Operator Forums
General Forums => Technical Central => : KB8OYR August 20, 2013, 07:39:22 PM
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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?
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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
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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.
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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
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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.