If you have an MFJ-259 antenna analyser is the analog SWR meter reading the same as the digital one?
Mine has always been a bit cock-eyed. The digital display is blob on but the analog meter is about .2 too high. i.e. a 50Ohm load shows 1.0 on the digital display and 1.2 on the analog one. 100Ohm shows 2.0 on the display and 2.2 on the analog one. It seems to have a constant offset with frequency.
Now it’s been like that since I got it 5+ years ago. I always the use the analog meter to show trends as that’s nigh on impossible on the digital display. So it’s a case of twiddle stuff and watch analog meter till it’s at minimum and then read actual value on the LCD. However, I’ve been using it a lot this weekend whilst playing with some ideas for antennas for 20m-10m and the offset is now bugging me. I’ve found calibration details on various websites but before I get the calibration hammer out I thought I’d ask to see if mine is squiffy or if this offset is typical.
Mine reads .2 to .3 high on the analogue swr display on my 80m vertical, 40m and 20m dipoles and pretty much any other HF antenna I’ve thrown at it. On 144MHz the discrepency is negligible though: it’s either spot on or at most .1 out. I’ve just checked my collinear which is tops 1.3:1 on the digi and reading 1.4:1 on the analogue meter at the lower band edge and same with the yagi at the upper band edge. The unit would be better if there was a fine adjustment or gearing on the frequency tune knob, it’s far too sensitive for my liking.
Tried yesterday to check out my 40/20m link-dipol with the MFJ and had the same experience.
It was the first time I noticed it!
So, as it is not a high precision tool (only with high price hihi) we probably have to live with it;
To be fair to MFJ, they acknowledge at the beginning of the 259 manual that “inexpensive impedance meters have limitations”. Having two readouts just makes us aware of one of the limitations.
It’s a bit like the old saying: a man with one watch always knows what time it is, but a man with two watches is never quite sure.
To be honest, the readout of the MFJ always was accurate enough for my needs but I normally do not hook up to the clock either. Well, except when having to pick up my XYL at the shopping centre may be
In reply to ON9CBQ:
My VK5JST analyser works ok with its single display and a delivered price of £75. I have to refine the calibration and can alter it per the PA0FRI pages of mods and improvements [joys of kit construction].
73
David
