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