"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.