J. McLaughlin wrote:
Most interesting. Thanks.

You're welcome. Just one small point, though:

I have not used the AEA-CIA for R-X measurements. I always assumed
that firmware was used to guess at the sign of X, and it is not too
surprising (though disappointing) that the chap who wrote the software
might blank out small values of X altogether.

In case anyone's not following this closely, I had been writing about
the AEA-CIA blanking out values of X less than about 30 ohms. That is
not "small" by any standard, and it only happened on one side of zero.
It could not possibly have been a deliberate feature of the programming.

In contrast, the MFJ-269 (and probably the 259B) does deliberately blank
out small values - truly small values, that is - as X passes through
zero. This occurs exactly as explained in the manual, and is exactly as
it should be.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

"Ian White, G3SEK" wrote in message
...
J. McLaughlin wrote:
Most interesting. Thanks.

You're welcome. Just one small point, though:

I have not used the AEA-CIA for R-X measurements. I always assumed
that firmware was used to guess at the sign of X, and it is not too
surprising (though disappointing) that the chap who wrote the software
might blank out small values of X altogether.

In case anyone's not following this closely, I had been writing about
the AEA-CIA blanking out values of X less than about 30 ohms. That is
not "small" by any standard, and it only happened on one side of zero.
It could not possibly have been a deliberate feature of the programming.

In contrast, the MFJ-269 (and probably the 259B) does deliberately blank
out small values - truly small values, that is - as X passes through
zero. This occurs exactly as explained in the manual, and is exactly as
it should be.
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

Ian, and others,

I have the 269 HF VHF UHF analyzer and noticed something strange. In
the "non-50 ohm" Advanced menu 3 mode, with the Zo set to 75 ohms, an
otherwise good 75 ohm load (please assume I know how to tell and I used a
low frequency to reduce errors) shows something like a 1.3 : 1 SWR. When I
called to ask about it, the first tech at MFJ seemed confused and clearly
did not understand. Another call, on another day resulted in a better tech,
but the response was to send it in for re-calibration. This also seems to
be a calculation rather than an adjustment, no?

Once you know Z it is a simple calculation to get to SWR for another Zo. Or
have I been smoking a bad brand...?

Woha! I see they have on line calibration manual for the 259B & 269 on
line!
http://www.mfjenterprises.com/MFJ-259Bcalibration.php
http://www.mfjenterprises.com/man/pd...alibration.pdf

I don't see anything other than "watch the blinking SWR" .(sounds like a
British insult) for the Advance 3 "calibration".

--
Steve N, K,9;d, c. i My email has no u's.

My MFJ 269 shows the SWR of a Tektronix 75 ohm termination as 1.0:1 up
to 77 MHz when Z0 is set to 75 ohms.

Roy Lewallen, W7EL

Steve Nosko wrote:

Ian, and others,

I have the 269 HF VHF UHF analyzer and noticed something strange. In
the "non-50 ohm" Advanced menu 3 mode, with the Zo set to 75 ohms, an
otherwise good 75 ohm load (please assume I know how to tell and I used a
low frequency to reduce errors) shows something like a 1.3 : 1 SWR. When I
called to ask about it, the first tech at MFJ seemed confused and clearly
did not understand. Another call, on another day resulted in a better tech,
but the response was to send it in for re-calibration. This also seems to
be a calculation rather than an adjustment, no?

Once you know Z it is a simple calculation to get to SWR for another Zo. Or
have I been smoking a bad brand...?

Woha! I see they have on line calibration manual for the 259B & 269 on
line!
http://www.mfjenterprises.com/MFJ-259Bcalibration.php
http://www.mfjenterprises.com/man/pd...alibration.pdf

I don't see anything other than "watch the blinking SWR" .(sounds like a
British insult) for the Advance 3 "calibration".

Thanks Roy. Mine shows it to measure 75 normally, but 1.3:1 in the Advanced
3 @75 ohms. Either I better change my brand of smokes or the Micro forgot
how to do the calculation... Better go back and try again to see it I
goofed somewhere...but I've done that several times...... . . . . .
.. .


Am I correct about this being simply a calculation?

--
Steve N, K,9;d, c. i My email has no u's.



"Roy Lewallen" wrote in message
...
My MFJ 269 shows the SWR of a Tektronix 75 ohm termination as 1.0:1 up
to 77 MHz when Z0 is set to 75 ohms.

Roy Lewallen, W7EL

Steve Nosko wrote:

Ian, and others,

I have the 269 HF VHF UHF analyzer and noticed something strange.
In
the "non-50 ohm" Advanced menu 3 mode, with the Zo set to 75 ohms, an
otherwise good 75 ohm load (please assume I know how to tell and I used
a
low frequency to reduce errors) shows something like a 1.3 : 1 SWR.
When I
called to ask about it, the first tech at MFJ seemed confused and
clearly
did not understand. Another call, on another day resulted in a better
tech,
but the response was to send it in for re-calibration. This also seems
to
be a calculation rather than an adjustment, no?

Once you know Z it is a simple calculation to get to SWR for another Zo.
Or
have I been smoking a bad brand...?

Woha! I see they have on line calibration manual for the 259B & 269 on
line!
http://www.mfjenterprises.com/MFJ-259Bcalibration.php
http://www.mfjenterprises.com/man/pd...alibration.pdf

I don't see anything other than "watch the blinking SWR" .(sounds like a
British insult) for the Advance 3 "calibration".

I'm sure it's a calculation. I believe it was you who pointed out that
once you know the Z, you can calculate the SWR for any Z0. And you don't
need to know the sign of the reactance in order to do it. So that's
surely the way it's done.

Can't imagine that yours does the calculation different than mine. . .
hm, maybe it does. . .mine says "Ver. 1.24" when it starts up. What does
yours say?

Roy Lewallen, W7EL

Steve Nosko wrote:

Thanks Roy. Mine shows it to measure 75 normally, but 1.3:1 in the Advanced
3 @75 ohms. Either I better change my brand of smokes or the Micro forgot
how to do the calculation... Better go back and try again to see it I
goofed somewhere...but I've done that several times...... . . . . .
. .


Am I correct about this being simply a calculation?

It's @home & I'm @work. I forwarded it home & will check. Mine is just
past 1 year old. oops.
Steve

--
Steve N, K,9;d, c. i My email has no u's.

"Roy Lewallen" wrote in message
...
I'm sure it's a calculation. I believe it was you who pointed out that
once you know the Z, you can calculate the SWR for any Z0. And you don't
need to know the sign of the reactance in order to do it. So that's
surely the way it's done.

Can't imagine that yours does the calculation different than mine. . .
hm, maybe it does. . .mine says "Ver. 1.24" when it starts up. What does
yours say?

Roy Lewallen, W7EL

Steve Nosko wrote:

Thanks Roy. Mine shows it to measure 75 normally, but 1.3:1 in the
Advanced
3 @75 ohms. Either I better change my brand of smokes or the Micro
forgot
how to do the calculation... Better go back and try again to see it I
goofed somewhere...but I've done that several times...... . . . . .
. .


Am I correct about this being simply a calculation?

Steve Nosko wrote:

I have the 269 HF VHF UHF analyzer and noticed something strange.
In the "non-50 ohm" Advanced menu 3 mode, with the Zo set to 75 ohms,
an otherwise good 75 ohm load (please assume I know how to tell and I
used a low frequency to reduce errors) shows something like a 1.3 : 1
SWR.

And it had correctly showed SWR=1.5 when Zo was set to 50 ohms?

When I called to ask about it, the first tech at MFJ seemed confused
and clearly did not understand. Another call, on another day resulted
in a better tech, but the response was to send it in for
re-calibration. This also seems to be a calculation rather than an
adjustment, no?

Once you know Z it is a simple calculation to get to SWR for another
Zo. Or have I been smoking a bad brand...?

I didn't check this feature as part of the review, but it should be
simply the inverse ratio of whatever resistances you choose to define as
your Zo values.

Woha! I see they have on line calibration manual for the 259B & 269
on line!
http://www.mfjenterprises.com/MFJ-259Bcalibration.php
http://www.mfjenterprises.com/man/pd...alibration.pdf

I don't see anything other than "watch the blinking SWR" .(sounds like
a British insult) for the Advance 3 "calibration".

The MFJ-269 had to go back after the review (which itself was a few
years ago) so unfortunately I'm no longer able to check your findings,
Steve.

But don't recalibrate it yet, because that would be stirring-in
additional variables which will muddy the waters right now. After the
present question has been resolved, you may be able to give the
calibration procedure a little more TLC than there was time for on the
production-line - but you'll need some precision standards to do it.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

"Ian White, G3SEK" wrote in message
...
Steve Nosko wrote:

I have the 269 HF VHF UHF analyzer and noticed something strange.
In the "non-50 ohm" Advanced menu 3 mode, with the Zo set to 75 ohms,
an otherwise good 75 ohm load (please assume I know how to tell and I
used a low frequency to reduce errors) shows something like a 1.3 : 1
SWR.

And it had correctly showed SWR=1.5 when Zo was set to 50 ohms?

Yep! An extensive sheck of known good loads showed that the MFJ was
working as expected with reasonable accuracy. I don't have numbers, but 50
ohm loads looked ok and SWR, Z etc all appeared to be reasonable. Just this
one problem. (I have access to Agilent "N" cal kits)



When I called to ask about it, the first tech at MFJ seemed confused
and clearly did not understand. Another call, on another day resulted
in a better tech, but the response was to send it in for
re-calibration. This also seems to be a calculation rather than an
adjustment, no?

Once you know Z it is a simple calculation to get to SWR for another
Zo. Or have I been smoking a bad brand...?

I didn't check this feature as part of the review, but it should be
simply the inverse ratio of whatever resistances you choose to define as
your Zo values.

Woha! I see they have on line calibration manual for the 259B & 269
on line!
http://www.mfjenterprises.com/MFJ-259Bcalibration.php
http://www.mfjenterprises.com/man/pd...alibration.pdf

I don't see anything other than "watch the blinking SWR" .(sounds like
a British insult) for the Advance 3 "calibration".

The MFJ-269 had to go back after the review (which itself was a few
years ago) so unfortunately I'm no longer able to check your findings,
Steve.

But don't recalibrate it yet, because that would be stirring-in
additional variables which will muddy the waters right now. After the
present question has been resolved, you may be able to give the
calibration procedure a little more TLC than there was time for on the
production-line - but you'll need some precision standards to do it.
--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

The problem is the I found nothing wrong when measuring in all the other
modes. Only this one problem and I believe this is a calculation in the
microprocessor, not anything that can be "calibrated" to correct. I was
asking if this is correct. I also see nothing in the MFJ cal procedure for
the 269 for this mode other than "watch the blinkin' SWR symbol" (I
indicates you have set a Zo other than 50.
--
Steve N, K,9;d, c. i My email has no u's.