Homemade coils to use a MFJ analyzer as a dip meter

Discussion in 'General Technical Questions and Answers' started by CT2FZI, Jan 15, 2010.

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  1. CT2FZI

    CT2FZI Ham Member

    Is anyone has the design of homemade coils to use a MFJ analyzer as a dip meter?

    I think that in Nov 1993 there was a QST article on this...

    I thank you in advanced,

    Luis, CT2FZI
  2. KA4DPO

    KA4DPO Ham Member

    All you need for frequencies of 1.8 to about 20 MHZ is a BNC connector and some 3/8 inch plastic tubing. Wind about 8 turns of #14 spaced one wire diameter and cover it with shrink tubing.

    I have the MFJ kit and have used it but the results are marginal in most cases. I prefer to use My Millen GDO which is far far more sensitive.
  3. CT2FZI

    CT2FZI Ham Member


    That is what I was looking for :)

    Luis, CT2FZI

  4. CT2FZI

    CT2FZI Ham Member

    Another answer:

    > You can try simply winding a few turns of hookup wire on a convenient
    > tubular form, hooked up to an RCA or BNC or PL-259 glued to the end of
    > the form, and see if you can get an adequate dipping for your
    > purposes.
    > The higher-frequency MFJ coil seems to be about 4 or 5 turns of wire -
    > length is about 1/2" and diameter is somewhere around 3/8". The
    > lower-frequency coil is somewhere around 12-14 turns of wire,
    > close-wound on a 1/2"-diameter plastic form.

    Source: http://newsgroups.derkeiler.com/Archive/Rec/rec.radio.amateur.antenna/2006-01/msg00804.html
  5. KA4DPO

    KA4DPO Ham Member

    Just remember that no matter how you fabricate it a proper Grid Dip Oscillator will work far better in every application.
  6. CT2FZI

    CT2FZI Ham Member

    Thanks! That is very true.

    I just want to take the full advantage of my MFJ analyzer, not just reading SWR...

    I would like to know what it can or can't do, and learn from it :)

    Like complex calculations... It will be fun!

    Luis, CT2FZI
  7. W5DXP

    W5DXP Ham Member

    I just had another brainstorm idea of how to use the MFJ-259B to find the resonant frequency of a trap. Cut a 1/4WL stub to exactly the trap target frequency. The MFJ-259B manual tells how to do that.

    Connect the trap to the open end of the stub and tune the MFJ-259B for the minimum impedance. When the minimum purely resistive impedance frequency is equal to the target frequency for the trap, the trap is tuned to the target frequency.

    Of course, this requires a 1/4WL stub per trap.
  8. CT2FZI

    CT2FZI Ham Member

    Thanks! I will see what the manual sais about it. Its a very good idea too.

    Luis, CT2FZI
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