Need help with MFJ Antenna Analyzer ...

Discussion in 'General Technical Questions and Answers' started by K4NYN, May 24, 2021.

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  1. K4NYN

    K4NYN Ham Member QRZ Page

    Help! My friend loaned me his MFJ 259B antenna analyzer to help me sort out some issues with my HF radios and dipole antennas. It was working great, and then I accidentally hit the mode and gate buttons simultaneously, and it went into advanced mode. I got it back into normal mode (I think), but now I get almost full deflection on the SWR and impedance meters on every antenna and every frequency. Even when hooked up to a known good antenna or a dummy load.

    Any help would be greatly appreciated.
  2. N3PM

    N3PM Ham Member QRZ Page

    Maybe if you take the batteries out for a few minutes and start again. Just a guess, but I have restored some other instruments by doing that.
    Mike N3PM
    K4NYN and WA9UAA like this.
  3. KE0ZU

    KE0ZU Ham Member QRZ Page

    Maybe going to the MFJ site and downloading AND READING the manual might help.
    W4HWD likes this.
  4. K4NYN

    K4NYN Ham Member QRZ Page

    Thanks, Mike. I tried that (and everything else). Called MFJ and they said to send it to them for repair, so I did. 73
  5. N3PM

    N3PM Ham Member QRZ Page

    Sorry that didn't work. Please be sure to let us know what they find.
    Mike N3PM
    K4NYN likes this.
  6. N7EKU

    N7EKU Ham Member QRZ Page

    And from the manual:

    Antenna SWR

    To measure SWR of an antenna or antenna tuner input:

    a.) If the antenna does not use a dc grounded feed system, momentarily short the antenna lead from shield to
    center. This prevents static charges from damaging the MFJ-259B’s zero bias detector diodes.

    b.) Immediately connect (in the case of a non-dc grounded feed system) the antenna lead to the MFJ-259B
    “ANTENNA” connector.

    I think MFJ has to repair quite a few of these due to this.

    K4NYN likes this.
  7. K4NYN

    K4NYN Ham Member QRZ Page

    Yeah, I was pretty careful about static discharge. Interesting thing is though, when I spoke to MFJ tech support, he was not like "oh yeah, you fried the sensitive diodes with static discharge, and this happens all the time." Maybe he was afraid that I would take it down to my bench and replace it myself for $0.70 or something, but he acted like this was something that he had never heard of happening before.

    I have to say that I am beyond disappointed with MFJ right now. In order to make sure that my friend had a fully working analyzer to prepare for our field day event, I shelled out $300 for the new 259D model analyzer and another $70 for the case for it. It arrived yesterday. Looks like it was assembled / remanufactured by drunken chimpanzees. The buttons are set in the metal case crooked, the screw heads are all stripped out, the case is bulged out on one side, the ohm meter does not work, and the metal case has edges on it so rough that you would think they cut them using a dull hatchet. The accuracy of it is seriously in question as well, as it is showing about a 16% discrepancy in SWR and impedance compared to my NanoVNA. My friend's older 259B was showing to be within 2% of the NanoVNA before it stopped working.

    I called Gigaparts, where I bought it, and the tech was less than surprised. He said that MFJ is having some serious quality control issues right now, and that he had personally switched over to all Rig Experts analyzers and gear due to similar issues. So now I am doubly stressed, as my expensive attempt to make my friend whole again has gone off the rails, and I am not sure what to do in order to get us a working and reliable analyzer for our field day preparations. Nothing makes me angrier than a company who touts that their products are made in the USA, and then lets their quality fall well below the standards of third world country sweat shops.

    I will continue to update this thread as events unfold, but I am very interested and grateful for any input from others on MFJ vs. Rig Expert vs. NanoVNA vs. other solutions and devices.

    Thanks and 73!
  8. N7EKU

    N7EKU Ham Member QRZ Page


    It is weird that it failed if you were careful with static. It can build up fast on an antenna in certain conditions, but if you were shorting the leads before connecting, it shouldn't have happened.

    If it is the diodes, you can replace them yourself but the work is SMD and you need to re-calibrate afterwards I think. The diodes are cheap to get however (probably like $10 shipped from Digikey).

    These are all based on the same basic detection method, just the Rig Expert and NanoVNA have advanced displays.

    I don't know why MFJ can't seem to solve these QC problems -- it's sad for sure.

    K4NYN likes this.
  9. K4NYN

    K4NYN Ham Member QRZ Page

    And to think, some people think hams are arrogant snobs. Are you trying to be helpful, or just sarcastic and facetious as the reply implies?
  10. KE0ZU

    KE0ZU Ham Member QRZ Page

    Perhaps, when one who seems not to know how to operate a particular piece of equipment, and in addition, seems not to have the "book of instructions" for same, asks for help, then, considers an honest suggestion as being "just sarcastic and facitious", might consider a little introspection.

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