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[TowerTalk] MFJ 259

To: <>
Subject: [TowerTalk] MFJ 259
From: (K4SB)
Date: Thu, 25 Jun 1998 14:19:21 -0700
> I am also curious of this. A good friend of mine bought one of the MFJ259's
> and when the UPS guy showed up with it we played with it for a few hours,
> and ended up calling MFJ and questioning their QC as well as their
> engineering.
> The major problem:
> It was reading erroniously, so we hooked it to a dummy load. Kinda funny
> the dummy load was showing 100 ohms on the meter and flat SWR.
> How can that be?
> It ended up going back to where it was bought from at the advice of MFJ.
> So please someone run this thing through some serious paces and please try
> the dummy load things, maybe we are just idiots and a 50 ohm dummy load is
> supposed to show 100 ohms???
> Mike...NO6X

I can think of several reasons, one being a contaminated piece of coax
used between the two.

I have run some checks on my older 2 259s and recalibrated them once.

Allowing for the fact that you just can't adjust a pot to a rch, the
units have always performed as expected. The frequency readout is always
within < .5 khz of my Omni VIB. The observed SWR on the antenna with
the MFJ agrees very closely with both a Bird, and a military spec
wattmeter I have. The MFJ has on more than occasion proven that the
velocity factor published for a particular type of coax is off by more
than 5%. Brand new coax, but from different runs. I've seen 50 ohm cable
with a published figure of .8 vary from .75 to .83. I always use a 1/2
electrical wave to tune any antenna I have up, and keep them hanging
on the wall with a 'do not use except for" practice. The vf for all 
these cables ( 80-10 ) was established by precise measurement ( well,
within 1/4" ) of it's physical length and then by measurement with the
MFJ. I use RG8X for all the cables. And each cable is cut to my 
favorite frequency. ( 80, 75, 40, 20 and 15 require 2 cables ) The other 
bands are a midpoint compromise. All of my units ( don't know exactly
how, but I've got 4 of them ) read from around 48 ohms to 50 ohms on
the dummy.

I have the grid dip accessories but rarely use them.

I suppose all this could be summed up as saying that before I adjust
an antenna, I know where I am with the test equipment. And I have to
remind myself of that every time I get a screwy reading and want to
think, " What's wrong with this unit." 



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