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MFJ-941 Versa Tuner II (The original one) Reading SWR w/ meter

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by N6JPA, Aug 8, 2019.

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  1. N6JPA

    N6JPA Ham Member QRZ Page

    I have an old MFJ-941 tuner. This is the original unit not a MFJ-941A thourgh F Unit. It does not have a cross meter needle like the later models and I'm try to figure out how to read reflected power when using the SWR to set it. If someone knows how or has a manual for it laying around I would appreciate any help. I have searched Google and Yahoo, but I'm only finding manuals for MFJ-941 A though F which have cross needles. TIA
    Keith KM6WIZ
     
  2. KM4DYX

    KM4DYX Ham Member QRZ Page

    Try pulling on the SWR/WATTS knob to switch between Forward and Reflected modes.
     
    KI4ZUQ likes this.
  3. N6JPA

    N6JPA Ham Member QRZ Page

    Thank you. That solved my problem. 73, Keith
     
    KI4ZUQ likes this.
  4. K7MEM

    K7MEM Ham Member QRZ Page

    Just FYI, not all of the MFJ-941 tuners, A through F, have cross needle meters. I have a MFJ-941D and it has a single needle meter just like your unit. The MFJ-941C also only has the single needle meter. But the C and D versions use buttons, rather than pushing/pulling on one of the knobs. Those, and the E version, are the only 941 manuals that I have. I didn't look any further.

    You might also want to stock up on diodes. When I bought my MFJ-941D used, the SWR bridge was blown out and the plastic cup for the open-wire balun was melted. That was OK with me, because the unit was going cheap. It was a simple fix, replacing the diodes, but mine has gone out twice since the original blow out. Otherwise, it works fine.
     
  5. N6JPA

    N6JPA Ham Member QRZ Page

    Thanks for the information Martin. When I received the tuner I opened it up to check everything and it is all still in tact. It is now accepting a load and I'm tuning a random length wire with no problems. I got lucky. :cool:
     
  6. N3PM

    N3PM Ham Member QRZ Page

    In reference to Martin's post on blown diodes, I've had them go bad from wind static, both fixed and mobile.
    Mike N3PM
     
  7. AA5MT

    AA5MT Ham Member QRZ Page

    When tuned, the reflected power should be near zero anyway. The only way to read reflected power at a non-resonant point is to tune the tuner into a 50 ohm dummy load first, and then switch to the antenna. Not really practical. Most radios have reflected power scales also.

    Tom
     
  8. KA1LHJ

    KA1LHJ Ham Member QRZ Page

    I have both the mfj 940b versa tuner from 1985 and the current mfj 872 wattmeter; if you can't find instructions for versa tuner you can download the instructions for 872; they work the same way.
    Set to forward power; that's button in versa tuner. While keying cw, turn the power meter, clockwise if I recall offhand, til the power reads maximum, 300, far right end of the scale. Stop keying, let the button out, then key to read swr.
     
  9. NK4Z

    NK4Z Ham Member QRZ Page

    I have an MFJ 941 Versa Tuner II. It seems the earliest model I can find on the web for instruction manuals is one for the 941C. Operation is essentially the same EXCEPT: There is no "fwd/ref" button. The sens/pwr knob pulls out to read reflected, pushes in to read forward power. SWR is readable on the meter if you attach a 50ohm dummy load, key down on the xcvr, and set the needle deflection for full scale (with the knob pushed in). THEN, switch from the dummy load to the antenna, pull the knob out and key down, and the meter should read SWR. Later models have an internal dummy load (very handy).

    1. Switch to dummy load
    2. PWR knob in
    3. Key down
    4. Turn dial to needle reads full scale
    5. Let off key
    6. Switch to antenna
    7. Pull knob out
    8. Key down
    9. Needle reads SWR

    Link for manual I found for the C model: https://ham-radio.ca/media/files/MFJ-941C_Tuner_Manual.pdf
    I hope this helps! I readlly appreciate this tuner. I use it on a poorly situated EFHW, and a fan dipole hidden in my attic. It works great.
     

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