Repairing a MFJ-259B Antenna Analyzer

I’ve had an MFJ-259B antenna analyzer for a while, and for the most part it’s been pretty good. However, in the last few months I’ve seen it intermittently give me really high SWR as opposed to normal SWR.

Usually, that means there’s a break in a transmission line somewhere, but I kept seeing it on different lines. Curiously, it usually went away when I touched the antenna connector.

I wondered if I was adding capacitance or something to the system, but finally I realized it happened when the feedline cable pulled down on the analyzer. It was just a break between the antenna connector and the analyzer.

I took the analyzer apart, re-soldered the SO-239 and I was back in business.

Here’s what I learned when I took the antenna analyzer apart:

  1. Take the battery cover off first (two screws on the bottom)
  2. Next, unscrew both sides (four screws on each side)
  3. At this point, you’ll have access to the battery compartment. Take out the two top batteries and the two bottom batteries (don’t need to take out the rest).
  4. You’ll see four screws that hold the battery compartment to the analyzer. Actually, that’s a lie – only the two right-side screws hold the battery compartment to the analyzer. The left screws are screwed into Delrin insulators. Don’t unscrew the left screws or the insulators will drop off and you’ll have to look under the table for them. Just unscrew the right screws (top and bottom).
  5. At this point you can move the battery compartment to the side, and get easy access to the SO-239 connector. Don’t lose the lock washers that are under the screws.
  6. I suspect they used lead-free solder to solder the connector, which is more prone to cracking than 60/40. I upped the heat a little and mixed in some 60/40 solder to make it more durable.
  7. At this point you can put the 4 batteries back in and test with a dummy load and a good cable. I did this and verified my problems with mystery SWR were gone.
  8. Put things back together in the reverse order that you took them apart.
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