Author Topic: rf choke values  (Read 10327 times)

KB8OYR

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rf choke values
« on: August 20, 2013, 07:39:22 PM »
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

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Re: rf choke values
« Reply #1 on: August 21, 2013, 07:27:10 AM »
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

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Re: rf choke values
« Reply #2 on: August 21, 2013, 06:51:25 PM »
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

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Re: rf choke values
« Reply #3 on: August 21, 2013, 08:48:44 PM »
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

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Re: rf choke values
« Reply #4 on: August 22, 2013, 08:09:53 PM »
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.