MFJ 259b Antenna Analyzer

[k3roj]

We had to insert this topic since the MFJ-259b has been a terrific tool on the workbench and in the field for the last few years. Having a portable unit like this makes it very easy to adjust antennas and check coaxial cable for faults. It requires 10 AA batteries for portable use and also has a 13 volt connector. There is only one little problem MFJ didn't think about when designing the exterior controls since the small red square on-off button up on the right hand corner protrudes just enough where it is too easy to push this button on, unknowingly draining the batteries down since there is no pilot light. I glued a round piece of plastic around the button, preventing accidental turning it on. The optional coils to use it as a grid dip meter comes in handy often to check resonance of inductors. I use the popular Buddipole vertical antenna for QRP operations in the field and here is a 9 minute YouTube video comparing tuning by adjusting the tuning coil for maximum noise and then using the MFJ259B which is more accurate. Here are many reviews of the MFJ-259b on E-HAM.

 

[Ham4CW]

I have to agree with you Alvin, I have an MFJ-259b also and found it to be an excellent tool.

The problem you mention with the power button sticking up above the front cover was sorted out by MFJ on later models.

Instead of the square red power button they now use a circular button which is housed within a raised surround. It is pretty well impossible to incidently switch on the MFJ-259b analyzer, in fact it can be difficult to switch the unit on even if you want to, especially if you have chubby fingers (the recessed button is quite tight).

I have one of the older models with the raised rectangular square button.

The other 'gripe' I have with these units is the charging system. They use what appears to be a constant current charging system, the current being handled by two small FETs. The problem is that the charge current is only arround 25-35mA, so if you fit a set of high capacity batteries it can take WEEKS for them to reach a full charge!

I got around this problem by bypassing the charge circuit with a 50-Ohm 5-watt resistor. With the particular adaptor I use the charge current is now more like 200-300mA so I can fully charge the unit in a few hours if I need to.

The internal oscillator and amplifier consume something like 160mA, though the auto sleep does a good job of saving your batteries if you have a 'senior moment' and forget to switch the unit off.

Despite what I've said I would still give the MFJ-259b 10/10 any day. I can't remember the last time I used my HF, VHF/UHF SWR meter, the MFJ-259b is just so handy!

73, Mark.

 

[4z5nu]

I always used my HF, VHF/UHF SWR meter, the MFJ-269b, with external 12v/7Ah rechargeable battery to check and trimm antennas with a good results. If you love this device then I recommend to put it in its protective cover as I did.
Regards, Dov aka 4Z5NU 73!