[TowerTalk] MFJ-259B vs Vectronics 584B ?
Fri, 2 Feb 2001 21:19:59 EST
I'm gonna take a crack at this and I hope I can explain without getting
laughed off the planet. There's a lot about +j and -j I still don't
I got mine yesterday. Comparing it to the MFJ catalog description, it looks
like the Vectronics model is an older and less sophisticated version of the
MFJ 259B. When you turn it on the Version is 1.1 and copyright 1998. It
might be comparable to the original MFJ 259.
It will measure SWR and the Magnitude of the impedance. It tells you the Z =
75 ohms. The manual says if the SWR is high and the Z is 50 ohms, "The load
is probably reactive." DUH -- even I know that. But it doesn't tell you the
reactance or whether it is inductive or capacitive.
It invites you to calculate by saying "the Magnitude of the impedance [Z) is
the square root of the addition of square of the resistance (R) and the
Reactance (X). By considering the definition of Z and by adjusting the TUNE
knob until the lowest SWR reading is obtained, it is possible to read the
antenna's pure reactance." So I guess whatever the Z is at the lowest SWR
tells you the reactance but I still don't know if it is inductive or
capacitive. Maybe I just don't know what I am looking at.
I understand the MFJ 259B will tell you the reactance (X) and the Phase (+j
Conclusion: The $149 Vectronics model is not an MFJ 259B. Sorry to break
the bad news. However, it looks like it would be a big help adjusting
antenna length, tuning stubs, finding shorts and opens, measuring velocity
factor and cable loss, testing baluns, measuring a capacitor or inductor, and
using as a grid dip meter or frequency counter.
BTW, even if it did tell me the reactance was +j120 I wouldn't know what to
do with the information. ;-)
Anyone else care to try explain all this, be my guest.
Fredericksburg, Virginia USA
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