Calibrating the MFJ 259B

Discussion in 'General Technical Questions and Answers' started by W8GRI, Aug 16, 2017.

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  1. W8GRI

    W8GRI Ham Member QRZ Page

    I have a nice MFJ-259B but it is not accurate. I compared it to a slightly newer 259B and it is off. My question is, if it is possible to re-align the unit. Either by myself or sending it in?

    Thanks in advance es 73 Rod W8GRI
  2. NN4RH

    NN4RH Premium Subscriber QRZ Page

    How far off? .

    For that matter, how do you know which one is off (or the most off). It could be the older one is better.

    Have you tried them with a good 50 ohm dummy load?

    The things were not designed or built to be high-precision instruments so they may both be "OK" as-is.
    Last edited: Aug 16, 2017
  3. W5DXP

    W5DXP Ham Member QRZ Page

    WB5YUZ likes this.
  4. K4SAV

    K4SAV Ham Member QRZ Page

  5. K8JD

    K8JD Ham Member QRZ Page

    I found the calibration info by using google, easy search.
  6. W8GRI

    W8GRI Ham Member QRZ Page

    I thank you all very much! This will help tremendously!

    VRY 73 Rod W8GRI
  7. W8AAZ

    W8AAZ Ham Member QRZ Page

    I have a used 259B and I thought I got a good price on it as it appeared to work OK at the hamfest. I put a 50 Ohm load on it, and noticed from a cold start, it reads impedance low. Like, it will be something like 35-40 Ohms and if I let it run a little while, it eventually rises up to a perfect 50 Ohms. Using one of those BNC 50 Ohm loads made for commercial terminations. Same with a 75 Ohm BNC load, it reads low too. Just a nuisance waiting for it to take 10 minutes or so to read right, and wastes battery power too. Once it is on the dot, everything seems to function fine. This is also on all ranges not just the high freq. range. Being solid state, I have to wonder what is "warming up". The battery check is OK at the beginning, 14.8 to 15 or so.

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