Question about RF chokes...

Discussion in 'General Electronics Chat' started by Mike33, May 1, 2009.

  1. Mike33

    Thread Starter AAC Fanatic!

    Feb 4, 2005
    Anyone know if there is a major difference between INDUCTORS and CHOKES?

    I have a 100uH RF choke - building one of those quicky metal detectors, and it calls for 220uH choke. Now, I also have resistor-style inductors that will easily get me 220uH, but not sure if the iron core is needed in this circuit (BFO type).

  2. David Bridgen

    Senior Member

    Feb 10, 2005
    No. Nor is there a minor one.

    As long as the value of inductance is correct, the core material (if there is one) is irrelevant.
  3. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
    The only difference is in the application. A choke is an inductor which is for the purpose of reducing or eliminating R.F. current flow in a specific part of a circuit. An inductor can also be used in a tank circuit, in which case its purpose is the exact opposite of a choke.

  4. bertus


    Apr 5, 2008
  5. eblc1388

    AAC Fanatic!

    Nov 28, 2008
    A choke is meant to block something or some frequencies. It can do its job even it has relatively large series resistance. Thus the series resistance is not quite as important as its inductance value. It is also cheaper to make.

    An inductor, or a RF inductor, on the other hand, need to resonant at some frequencies and thus would require higher Q to do it jobs better. This translates to low series resistance.

    So if a circuit calls for a tank(L and C) with 200uH, then a 200uH choke would work badly or not at all.
  6. Mike33

    Thread Starter AAC Fanatic!

    Feb 4, 2005
    Thanks for the replies, guys - informative since I mostly work on audio FX, amps, and that sort of for a metal detector circuit, I probably should go get a second RS iron-core choke (they come 100uH, project calls for 220uH RF Choke, so I would series them). I was curious if Q was an issue, since it's a tank circuit; it probably is and therefore standard inductors may not work.

    I'm trying to put together the circuit linked below, for use on job sites where I tend to have nails flying all over the place - just a toy to pass over the ground at the end of the job to see if any are hiding. I'll also have to build a "faraday cage" around the sensing coil; probably just a foil shield around whatever I put the coil in, that is grounded.
    Make sense?
    Thanks again! I'm going backwards - branching out from audio to other types of electronic projects.