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Gates M-5693 Modulation Monitor

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

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  1. W2WDX

    W2WDX Subscriber QRZ Page

    @AC0OB OK ... I know you're right about the roller inductor after thinking it through. I know from static/lightning coils I use on open-wire feeder the inductance is high at 340uH or higher and never had a problem loading any of my gear at amateur frequencies, so yes a roller would not have enough inductance and be problematic for any tank circuit.

    OK ... toroid and coax center conductor it is. Much simpler, LOL. Dennis .... grrr ... ya got me all excited. I thought I finally found a use for those rollers!!!
  2. N1BCG

    N1BCG Ham Member QRZ Page

    This thread has inspired the restoration of a 5693 that hasn't been used since the early 80s. During the process, I discovered a discrepancy with the schematic I have. The two RF diodes appear to have been replaced with four and even they don't appear to match each other.
    Any thoughts on using modern day diodes to replace the 1N39(?) diodes? The parts list shows CR1 and CR2 as "Germanium Diodes".

    IMG_8193.JPG RF_In.jpg
  3. W2WDX

    W2WDX Subscriber QRZ Page

    Last edited: Jul 15, 2018
  4. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    N1BCG likes this.
  5. N1BCG

    N1BCG Ham Member QRZ Page

    There’s been a lot of improvements in semiconductor technology in the past 60 years so I’m leaning toward using new ones.

    Also, a second manual shows 4 of these diodes (pairs in series) so the number seems correct. What’s in there now are two 1N914 and two unid diodes. This probably explains the slightly distorted audio at the “Measure Fidelity” output fed from the detectors. The unit doesn’t even need to be powered up for this.

    Time for a fresh start...
  6. KL7AJ

    KL7AJ XML Subscriber QRZ Page

    Boy, you sure wobbled a few nostalgia glands here! It should be a great instrument for 160 with no modification, other than twiddling the antenna trimmer. You might want to remove a few caps in the front end if you need some high band utility.
  7. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    Yeah, I would think by simply lifting or removing C1 and adjusting C2 and XT2, one could easily move up to 160m with the High-Range coil.


    Attached Files:

  8. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    What's a "unid" diode?

  9. W2NBC

    W2NBC Ham Member QRZ Page

    Well, methinks that just like the word "unid"..

    It's "UNIDentified" ..;)
    N1BCG and AC0OB like this.
  10. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    Or, it could have been "Unidirectional" which wouldn't make any sense either.:D


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