I think Richard is unnecessarily complicating the matter. Assuming you
have a directional wattmeter, you determine the power at the line input
by subtracting the "reverse power" from the "forward power" at that
point. The power at the line output is determined the same way. 10 times
the logarithm of the ratio of the input power to output power is the
line loss in dB.

Use or even knowledge of mismatch loss isn't necessary. In fact,
attempting to apply it to the problem at hand will very likely lead to
incorrect conclusions.

Roy Lewallen, W7EL

Richard Clark wrote:
On 30 Jul 2007 18:50:13 GMT, Ed
wrote:

I think I need to just haul my Wattmeter up to the feedpoint and
measure the loss for myself!

Hi Ed,

That won't fully demonstrate the magnitude of the problem either. The
Wattmeter will only be calibrated into a matched load and if you
provide the matched load, then you won't suffer the Mismatch Loss
(where the drama of this soap opera resides).

You will then be back into a technical discussion complete with loss
multipliers or transmission line mechanics that will act as a narcotic
to your audience. If you supply the mismatch then you are going to
have to juggle the forward and reverse powers (and explain why forward
isn't as high coming out as it is going in the line).

The result is the appearance of a game of three card Monte .

You may as well treat them like full-fledged technicians and lay out
the entire problem from the beginning with a technical solution at the
end.

73's
Richard Clark, KB7QHC