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MicroMatch MM-2

Discussion in 'General Technical Questions and Answers' started by W1FIT, Apr 19, 2013.

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  1. W1FIT

    W1FIT Ham Member QRZ Page

    This is my first post and hope I'm in the right place. I have an MC Jones MM2 SWR/Power Meter and haven't a clue (or a manual) on how it works. It has a pot on the front but that's it. How I differentiate between coming and going is a mystery. I'm not even sure if the n and the out ports are identified properly since the back panel fits both ways.

    I was hoping to use it with my newly acquired NCX-3. I have a new license and have surrounded myself with old things (like me).


    Thanks for any help.
     
  2. W9GB

    W9GB Ham Member QRZ Page

    Joe -

    M.C. Jones Electronics was based in Bristol, CT. ‚ÄčI believe Bendix Corp. acquired the company.

    Sounds like you have the coupler unit for this meter??
     

    Attached Files:

    Last edited: Apr 20, 2013
  3. K8JD

    K8JD Ham Member QRZ Page

    Using the SWR meter

    Most simple SWR meters work like this;
    Select forward on the function switch.
    Generate a low power carrier from your rig. (I hope you realize just keying a transceiver in SSB mode produces ZERO output)
    Set the pot for maximum on the meter scale.
    Switch to reflected on the function switch and read the SWR !
    Stop transmitting.
     
    Last edited: Apr 20, 2013
  4. K8JD

    K8JD Ham Member QRZ Page

    The National Radio NCX3 was my first SSB rig, in the late 60's, and at $129 used, it was affordable for me.
    It was tricky to use , with no ALC to limit voice peaks and no CW offset to hear CW on the transmit frequency correctly.. Broad receiver like a barn door !
    I eventually had to build a mic audio compressor/peak limiter so I would not flat top the voice peaks and cause splatter.
    I had to borrow an oscilloscope to get it set properly.

     
    Last edited: Apr 20, 2013
  5. W1FIT

    W1FIT Ham Member QRZ Page

    No, I have the one pictured. mm-2.jpg

    What's puzzling is that there is no forward or reverse switch.

    Thanks for any suggestions.
     
  6. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    That is a bit weird, never saw the meter without the switch.

    I've had several Jones Micromatch units with separate meter boxes and couplers over the years and the meter always had a switch.

    Jones Micromatch.png
     
  7. K8JD

    K8JD Ham Member QRZ Page

    So you have to unscrew the PL259 connectors going to the box and reverse them to go from fwd to ref power. That or install the switch.

     
  8. W1FIT

    W1FIT Ham Member QRZ Page

    Thanks to all. I've figured out that reversing the connectors would probably work but be no fun at all. I would be thrilled to install a switch if I knew where to connect. Any ideas or suggestion?
     
  9. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    That would be easy to answer if we knew more.

    The "plug" and wiring that interconnects the sampler with the meter: Is it 3-conductor, using a 3-conductor plug?
     
  10. W1FIT

    W1FIT Ham Member QRZ Page

    mm2-back.jpg OK, Thanks. Here is what I have. Shield is one end of pot. white wire is other end of pot. Shield goes to one side of meter as well, not marked for polarity. Middle (wiper) of pot goes to other side of meter, also unmarked. Picture included.

    If you think that this can be reversed, then this is not the garden variety meter movement, e.g. x no. of dc microamps.

    Again, thanks for help and insight.
     
  11. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    That connection doesn't allow for a "switch," as it's obviously not bring both "forward" and "reflected" current data from the coupler to the meter housing. So, looks like you're stuck with swapping the coax connections around if you want to know what reflected power or SWR is.

    The MicroMatch couplers I've had have three wires coming from the coupler to the meter box: A forward wire, a reflected wire, and a common (shield). Using a switch on the meter housing, it swaps what drives the meter from "F" to "R."

    Although the meter may not be marked for DC microamps, it is. Probably 0-50 or 0-100 uA. Wouldn't be difficult to measure it and see.
     
  12. W1FIT

    W1FIT Ham Member QRZ Page

    OK. Any way to figure out how to get current from the "other" direction?

    Thanks again.
     
  13. W9GB

    W9GB Ham Member QRZ Page

    The MAGIC happens in the coupler for the meter with the Germanium or Schottky diodes.

    Here is the NA0TC tutorial, scroll down to Dual Directional Coupler.
    http://www.na0tc.org/Homebrew SWR Meter.pdf

    Almost every ARRL Handbook covers this, plus DIY Build project.
     
  14. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    I am unfamiliar with that particular coupler, so I don't know if it even has separate "forward" and "reflected" circuits. It might, but it might not.

    If not, without rebuilding the coupler there would be nothing you could do to actually measure SWR by virtue of F/R indications.

    Why not take the coupler apart and see what's in there?
     
  15. W9GB

    W9GB Ham Member QRZ Page

    That will be required to understand (reverse engineer, draw schematic) current coupler design.
    Some form of Directional Coupler.
    I have never seen a diagram or the sensor M.C. Jones used in this model.

    A FWD and REV might be possible with simple additions/modification,
    BUT without current schematic -- that is conjecture.

    Tandem Match Coupler can be found in 2010 Antenna Handbook (ARRL).
     
    Last edited: Apr 26, 2013
  16. W1FIT

    W1FIT Ham Member QRZ Page

    Thanks to all. I have my work cut out.
     
  17. WB2WIK

    WB2WIK Premium Subscriber QRZ Page


    It's not much work. Open up the coupler and see what's in there. Either it has two diode detectors on opposite ends of a coupling system, or it doesn't. This should take about 60 seconds to resolve.
     
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