On Fri, 4 Oct 2019 at 13:38, Martin via Groups.Io <martin_ehrenfried=
[email protected]> wrote:
Hi All,
Just about every instrument I can remember using, has RL shown as a
negative curve, even if the units themselves are positive. This is handy if
for example you are tuning a filter, as you can see the insertion gain on
the uppermost trace and the RL loss on the lower one without them
overlapping. It also matches the convention of SWR plots and when
measuring the RL of cables it matches the convention of more attenuation
being negative.
However Owen makes the point that negative loss is actually gain (double
negative) and vice versa, and the existing conventions do indeed lead to
confusion and mistakes being made. Maybe return loss should really be
called return gain, and then everyone would be happy (well maybe - but this
is not a serious suggestion).
*As soon as I looked at Rune's software, I thought "Return loss should not
be negative",* but I did not comment. There was a note in an IEEE article,
where the editor stated he has seen negative values, made the argument for
why a return loss should be positive, and expected authors to correct this.
But I have come to the conclusion that this is like arguing religion. You
are unlikely to convince a believer of religion X that he/she is wrong, and
religion Y is right, so you might as well give up!
Regards,
Martin - G8JNJ
--
Dr David Kirkby Ph.D C.Eng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, CHELMSFORD,
Essex, CM3 6DT, United Kingdom.
Registered in England and Wales as company number 08914892
Tel 01621-680100 / +44 1621-680100
