Ham Operator Forums

Please login or register.

Login with username, password and session length
Advanced search  

News:

SMF - Just Installed!

Author Topic: rf choke values  (Read 3674 times)

KB8OYR

  • Newbie
  • *
  • Posts: 5
    • View Profile
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?
Logged

W7TFO

  • Newbie
  • *
  • Posts: 6
    • View Profile
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
Logged

KB8OYR

  • Newbie
  • *
  • Posts: 5
    • View Profile
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.
Logged

W7TFO

  • Newbie
  • *
  • Posts: 6
    • View Profile
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
Logged

KB8OYR

  • Newbie
  • *
  • Posts: 5
    • View Profile
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. 

Logged