Gates M-5693 Modulation Monitor

Discussion in 'Amplitude Modulation' started by W2WDX, Jul 11, 2018.

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  1. N1BCG

    N1BCG Ham Member QRZ Page

    ^^ yes, that.

    I should have written it as unID.

    Oddly, I substituted four 1N914 diodes and didn’t notice much difference.


    Also, I found out that this model tunes 1200-2500kc without changing the input tuning.
    Last edited: Jul 16, 2018
  2. KL7AJ

    KL7AJ XML Subscriber QRZ Page

    While you may have adequate sensitivity well outside the nominal tuning range of the input, it's important to be able to tune it for a peak to assure sideband symmetry....important for accurate modulation depth measurement.
    AC0OB likes this.
  3. N1BCG

    N1BCG Ham Member QRZ Page

    Should have been written:

    “...this model, designed for the upper BCB, tunes 1200-2500kc without changing the fixed input tuning circuit values.”
  4. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    The bandwidth of the input tuned circuit of the M-5693 is rather wide, but it was also meant to be peaked to the station's frequency so, as AJ stated, the detection of the full modulation envelope would be symmetrical with respect to the station's center frequency.


  5. N1BCG

    N1BCG Ham Member QRZ Page

    A clarification of the clarification...

    “Adjustment of the variable capacitor allows peaking of carrier frequencies between 1200 and 2500 kc. Changes to fixed value components in the input circuit would be required for use outside of this range.”
  6. W2WDX

    W2WDX Subscriber QRZ Page

    Well said ... I think ... maybe .... wait could you clarify that. Some of the fixed value components you refer to are not ... fixed ... that is. Wait ... I need to clarify that. The step up transformer is varia ... wait .... Aw geez ... now I just confused myself.
  7. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    I think he was saying something similar to what I said in the above post.

    N1BCG likes this.
  8. W2WDX

    W2WDX Subscriber QRZ Page

    So getting back this ... If I take a variable coils that can adjust from say 1uH to 30uH, could I take some magnet wire and wrap a few turns to make a primary ... no right it would vary as well. I think I just answered myself. LOL.

    So I should just wind some fixed transformers myself on a coil form and build up separate transformers for each band. I have the big brown Millen coil forms and have some four pin small coil forms like what is inside the brown thing. I could just duplicate this transformer and use the values you gave above (for each band) on the secondaries. Here's the original Gates transformer:

    trans1.JPG trans2.JPG trans3.JPG
  9. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    I think you said this transformer is tuned via a variable core (such as a ferrite core) moving up and down?

    My calculations were for an open air coil with no core. If it has a ferrite core, then you may only need 1/3 to 1/2 half that inductance that was calculated since the core is going to have a major effect on increasing the total inductance.

    Hopefully you have an inductance meter to help you with this?

  10. W2WDX

    W2WDX Subscriber QRZ Page

    I haven't taken this xformer apart, but I wonder if I could carefully take some of the windings off the secondary and get it down to the range where I need it. I'll have measure this one first, since for all we know this not the original and in fact be a modded piece already. I don't know the provenance of this MM.

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