Hi all

I'm looking at purchasing an MFJ269 antenna analyser and keen to hear
experience of others in this group regarding this or similar analysers.
Appears to be ideal if it is as good as MFJ claim.


--
Peter VK6YSF

http://members.optushome.com.au/vk6ysf/vk6ysf/main.htm

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Peter wrote:
Hi all

I'm looking at purchasing an MFJ269 antenna analyser and keen to hear
experience of others in this group regarding this or similar analysers.
Appears to be ideal if it is as good as MFJ claim.


A good place to check for reviews is at eham.net.

http://www.eham.net/reviews/
http://www.eham.net/reviews/detail/803


- --
Best Regards, Keith
http://home.comcast.net/~kilowattradio/
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"Keith" wrote in message
...
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Peter wrote:
Hi all

I'm looking at purchasing an MFJ269 antenna analyser and keen to hear
experience of others in this group regarding this or similar analysers.
Appears to be ideal if it is as good as MFJ claim.


A good place to check for reviews is at eham.net.

http://www.eham.net/reviews/
http://www.eham.net/reviews/detail/803


- --
Best Regards, Keith
http://home.comcast.net/~kilowattradio/
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Thanks for the links Keith

Regards

--
Peter VK6YSF

http://members.optushome.com.au/vk6ysf/vk6ysf/main.htm

Peter wrote:
Hi all

I'm looking at purchasing an MFJ269 antenna analyser and keen to hear
experience of others in this group regarding this or similar analysers.
Appears to be ideal if it is as good as MFJ claim.

I have one and find it extremely handy for a variety of tasks such as
measuring the length or velocity factor of coax lines or the impedance
of ferrite cores. But ironically, the one thing it's almost completely
useless for, at my QTH, is analyzing antennas. Induced fields from TV,
FM, and AM broadcast stations are so high that the MFJ isn't able to
detect its own signal. This isn't unique to the MFJ -- I've had the same
problem with a very expensive HP digital impedance meter, and revert to
my old GR bridge with a tuned receiver for a detector when I want to
actually measure an antenna's impedance. For me the MFJ is worthwhile
just for the other functions it provides, but it might or might not be
for you. Just keep in mind that, depending on your QTH, it might not be
able to actually measure antenna impedances.


Roy Lewallen, W7EL

"Roy Lewallen" wrote in message
...
Peter wrote:
Hi all

I'm looking at purchasing an MFJ269 antenna analyser and keen to hear
experience of others in this group regarding this or similar analysers.
Appears to be ideal if it is as good as MFJ claim.

I have one and find it extremely handy for a variety of tasks such as
measuring the length or velocity factor of coax lines or the impedance of
ferrite cores. But ironically, the one thing it's almost completely
useless for, at my QTH, is analyzing antennas. Induced fields from TV, FM,
and AM broadcast stations are so high that the MFJ isn't able to detect
its own signal. This isn't unique to the MFJ -- I've had the same problem
with a very expensive HP digital impedance meter, and revert to my old GR
bridge with a tuned receiver for a detector when I want to actually
measure an antenna's impedance. For me the MFJ is worthwhile just for the
other functions it provides, but it might or might not be for you. Just
keep in mind that, depending on your QTH, it might not be able to actually
measure antenna impedances.


Roy Lewallen, W7EL

Roy

All comments noted. I do in fact live within 2km of an AM transmitter
although I believe it's not that high powered and I also have an FM
transmitter within 5km, therefore I'm interested in the details of your
location in relation to the various transmitters.

Regards
--
Peter VK6YSF

http://members.optushome.com.au/vk6ysf/vk6ysf/main.htm

Peter wrote:

Roy

All comments noted. I do in fact live within 2km of an AM transmitter
although I believe it's not that high powered and I also have an FM
transmitter within 5km, therefore I'm interested in the details of your
location in relation to the various transmitters.

Regards

Roughly 10 - 15 miles from here is a ridge about 800 feet higher than my
location. On top are virtually all the TV and FM, and a number of the
AM, transmitters for the Portland Oregon metropolitan area. A single
strong transmitter is likely to be enough to confuse an antenna
analyzer, though. Filtering is possible, of course, but you have to take
care to design filters to have minimal effect on measured impedances
while still filtering effectively. This can sometimes be challenging
depending on the strength of the interfering signal and how far it is
from the measurement frequency.

I also have to be careful when working on audio circuitry -- on several
occasions I've tracked down "hum" as demodulated TV video, and I end up
having to include VHF decoupling and shielding to audio circuits. Don't
know much about the nature of HDTV signals, but it might not be so bad
if it doesn't have as much energy in the AF range when demodulated. It's
bound to drive untuned antenna analyzers bonkers, though.

Roy Lewallen, W7EL

On Sat, 15 Aug 2009 22:47:05 -0700, Roy Lewallen
wrote:

Peter wrote:
Hi all

I'm looking at purchasing an MFJ269 antenna analyser and keen to hear
experience of others in this group regarding this or similar analysers.
Appears to be ideal if it is as good as MFJ claim.

I have one and find it extremely handy for a variety of tasks such as
measuring the length or velocity factor of coax lines or the impedance
of ferrite cores. But ironically, the one thing it's almost completely
useless for, at my QTH, is analyzing antennas. Induced fields from TV,
FM, and AM broadcast stations are so high that the MFJ isn't able to
detect its own signal. This isn't unique to the MFJ -- I've had the same
problem with a very expensive HP digital impedance meter, and revert to
my old GR bridge with a tuned receiver for a detector when I want to
actually measure an antenna's impedance. For me the MFJ is worthwhile
just for the other functions it provides, but it might or might not be
for you. Just keep in mind that, depending on your QTH, it might not be
able to actually measure antenna impedances.


Roy Lewallen, W7EL
I live in a very rural area and mine works as advertised.

I don't use it very much because it gives quick and complete answers.

"Peter" wrote in
. au:

Hi all

I'm looking at purchasing an MFJ269 antenna analyser and keen to hear
experience of others in this group regarding this or similar analysers.
Appears to be ideal if it is as good as MFJ claim.



Peter,

Effective exploitation of the capability of this type of analyser depends
on a sound understanding of transmission lines, and of the instrument's
own limitation. The availability of these analysers at low cost, and the
perception that they are a magic bullet has lead to a lot of pseudo
technical nonsense being proposed. The magic is more in the user's
capability than the box, and buying the box doesn't buy knowledge and
understanding... but the device can help develop knowledge and
understanding.

I have not used a '269 (though I have extensively used a '259B), but I
suspect that it does not display the sign of X. Estimation of the sign of
X in the '259 and similar instruments is an issue, and confuses many
users. There are propositions that sign of X is easily determined from
the slope of X with frequency at a point... but whilst that is true for
an ideal passive component, it is not true in general.

These instruments are often used in pursuit of the questionable goal of
resonance, and the instrument used to show resonance by observing X=0, or
X approximately zero, or a local minimum for X at some frequency on the
assumption that X changes sign at that point and that resonance of
something is indicated.

I wrote some notes entitled "In pursuit of dipole resonance with an
MFJ259B" at http://vk1od.net/blog/?p=680 that canvasses the behaviour of
the instrument in such an application, and flags the issues in
measurement. You may find them interesting.

Others have raised the issue that these instruments use a broadband
detector, which works fine so long as the internal oscillator has low
harmonic content and dominates the detector. If you let one of these
things time out, the oscillator is shut down, and if you see indication
on the meters, then energy from another source is of sufficient magnitude
to be concerned about the accuracy of measurements.

Owen

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

Hi all

I'm looking at purchasing an MFJ269 antenna analyser and keen to hear
experience of others in this group regarding this or similar analysers.
Appears to be ideal if it is as good as MFJ claim.



Peter,

Effective exploitation of the capability of this type of analyser depends
on a sound understanding of transmission lines, and of the instrument's
own limitation. The availability of these analysers at low cost, and the
perception that they are a magic bullet has lead to a lot of pseudo
technical nonsense being proposed. The magic is more in the user's
capability than the box, and buying the box doesn't buy knowledge and
understanding... but the device can help develop knowledge and
understanding.

I have not used a '269 (though I have extensively used a '259B), but I
suspect that it does not display the sign of X. Estimation of the sign of
X in the '259 and similar instruments is an issue, and confuses many
users. There are propositions that sign of X is easily determined from
the slope of X with frequency at a point... but whilst that is true for
an ideal passive component, it is not true in general.

These instruments are often used in pursuit of the questionable goal of
resonance, and the instrument used to show resonance by observing X=0, or
X approximately zero, or a local minimum for X at some frequency on the
assumption that X changes sign at that point and that resonance of
something is indicated.

I wrote some notes entitled "In pursuit of dipole resonance with an
MFJ259B" at http://vk1od.net/blog/?p=680 that canvasses the behaviour of
the instrument in such an application, and flags the issues in
measurement. You may find them interesting.

Others have raised the issue that these instruments use a broadband
detector, which works fine so long as the internal oscillator has low
harmonic content and dominates the detector. If you let one of these
things time out, the oscillator is shut down, and if you see indication
on the meters, then energy from another source is of sufficient magnitude
to be concerned about the accuracy of measurements.

Owen

Thanks Owen for the information and your notes "In pursuit of dipole
resonance with an MFJ259B"
My intended use for the device is to get a bit of view on what's going on
with my various home brew antennas and matching devices and for my own
curiosity to compare theory with real world.

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

Regards


Peter VK6YSF

http://members.optushome.com.au/vk6ysf/vk6ysf/main.htm

"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