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[W1VT]

http://www.ac6la.com/tldetails1.html
You can use AC6LA's TLdetails to calculate the impedance the analyzer should see when there is 25" of coax between the resistor and the antenna analyzer.  Don't forget that it varies with both the coax type and frequency.

Zack W1VT

[KI4DSC]

I have a trouble ticket started with MFJ. If it is not too expensive I will send it for repair. I have been using thus unit for several years and this problem came on all at once. When the unit he's an open line, it reads around 200+0j ohms. When I hook up to a 550 ohm resistor it reads 230+0j ohms. When I put the shorted test connector on it reads 30+0j ohms. When I hook it to my 80m dipole through the tuner and spin the inductor, I get only small variations and never more than 10j. When it was working properly the unit would go off the scale and back.

It's definitely broke.

[AA7LX]

I would recommend purchasing a RigExpert AA-170; which is good to 170Mhz. I had MFJ Analyzers for many years and had many problems with grounding and capacitance loading/errors. I finally gave up and spent 339.00 Dollars for a RigExpert AA-170. It's "Light Years" ahead of the MFJ. I personally wouldn't brother sending your Analyzer to MFJ(unless it's under Warranty). Most of the Reviews posted on eHam display great frustration with anything MFJ. 73' George, AA7LX   

[NA4IT]

The MFJ-259 is affected by strong AM broadcast band signals.

One way to tell if this is the problem is to take measurements during the day and at night. Most AM BC stations substantially reduce power at night.

That's what I was going to say. We used to do field day about 1/2 mile from an AM station. Analyzers wouldn't work, and we had to use link coupled tuners to tune antennas (Johnson Matchboxes).

[KI4DSC]

All fixed....    I sent the MFJ analyzer back to MFJ and they replaced the 4 bridge diodes just as I suspected.  Wish I had the equipment and ability to solder SMT components -- I could have fixed it myself.

Anyhow, I sent the unit out to MFJ on November 10 and it was back in my hands on November 21.  11 days including shipping.  Way faster than I ever expected.  I thought for sure it would be weeks and weeks before it was done.