"Peter" wrote in
. au:


"Dale Parfitt" wrote in message
...

"Peter" wrote in message
...

"Owen Duffy" wrote in message
...
"Peter" wrote in
. au:

...
I must admit I had assumed that the 269 analyzer display the sign
of the reactance, I will have to reread the ad.

Ah, you were looking for honesty in advertising!

The online guff on the MFJ259B says:
"Read Complex Impedance as series resistance and reactance (R+jX)
or as magnitude (Z) and phase (degrees)."

The MFJ259B definitely does *not* show phase angle or reactance as
negative for cases where X is actually negative.

The same words appear in the MFJ269 online page, so it may also be
a misrepresentation.

I see in the MFJ269 manual, the same pretence over the sign of
phase and reactance. It contains the words "Besides Z, an angle
between zero and 90
degrees is shown. This angle represents the phase difference
between current and voltage at the terminals of the analyzer."

Of course, a phase angle between "zero and 90 degrees" does not
represent
"phase difference between current and voltage at the terminals of
the analyzer" in the case of a capacitive impedance.

Honesty in advertising... think again.

Owen

What was I thinking! I was impressed with what was being claimed.

I will continue with my product research and you can expect me to
float some other manufactures device on this group soon for
comments.

Peter VK6YSF

Again- look at the RigExpert A-200A. Batteries seem to last forever,
it's USB upgradable and it DOES resolve the sign of R +/-JX.

Dale W4OP
Thanks Dale

I have just had a look at the RigExpert site. Look impressive, but the
MFJ269 at about $400US was about my limit.
I think I will take a step back and conduct a more scientific review
of all of the antenna analyzers on offer, there for you should get
sick of my postings over the next couple of weeks/months.
I must say that the ability to save and analyze data on the lap top is
an appealing feature.

Peter,

It helps to identify what you really need from the instrument. The
difficulty in doing that is foreseeing where an unstructured learning
journey might take you.

You will tend to arrive a points where you want to measure something just
beyond your existing capability. If the quest is for pure learning, then
just concentrate on the things that are within scope, and enjoy the
learning.

I admit that it is a bit of an old world view of ham radio, that it is
quintessentially a technical learning activity... but call me a dinasour.

The resolution of sign with the '259B is not a show stopper, but it is a
convenience issue and in the hands of a person with inadequate knowledge,
it is potentially misleading.

TLLC (http://www.vk1od.net/calc/tl/tllc.php) can refer impedance made at
one point on a known transmission line (eg the tx end) to another point
(eg the load end). Of course, uncertainty of the TL parameters
contributes to measurement uncertainty. This technique is ok for one off
measurements, but would be very labour intensive for a sweep with
hundreds of observations.

The ability to calibrate the feedline 'fixture' as part of a VNA
measurement system provides the convenience of measurement referred to
your preferred reference plan. The AIM4170 is (as I understand it) half
of a VNA, but that should be enough to do the same thing.

So, for the advantages of the ham grade VNA over the MFJ259B, you pay
more money, get better measurement resolution (the AD converters have
better resolution than the MFJ259B), have capability for automation of
measurement referred to a convenient reference plane, but... you lose
portability... though there is no reason why a ham grade VNA with a basic
display system couldn't be portable.

Owen