On 9/28/2015 11:47 AM, Ian Jackson wrote:
In message , rickman writes



Definition of Return Loss

In technical terms, RL is the ratio of the light reflected back from a
device under test, Pout, to the light launched into that device, Pin,
usually expressed as a negative number in dB.

RL = 10 log10(Pout/Pin)

Here is a link for a table of return loss and VSWR....

http://www.jampro.com/uploads/tech_d.../VSWRChart.pdf

It shows a higher return loss (assuming you mean magnitude since the
values are all negative) for lower VSWR.

I'm surprised to see negative quantities. For 50 years, I've always
understood the Return Loss Ratio (RLR) to be exactly what it says on the
tin, ie the ratio (in dB) of the LOSS (the attenuation) of the reflected
signal wrt the incident signal. This is a +ve quantity. Things are
already sufficiently confusing without having to start thinking in
unnecessary -ve figures!

The ratio is not larger than one. So the log will be zero or less. In
dB the value will be negative for any reflection other than none.

--

Rick