"Jimmie D" wrote in
:

I think I have given enough info. But I will try yo expess it in
another way.
Power delivered to the antenna but be maintained with in +- 1 db in
this case that power is 100 watts. Power is normally
checked at the TX and recorded after allowing for line loss as "power
at
the antenna". Power checks are done on a weekly basis. Once a year the
line loss is measured and this value is used to subtract from the
power at the transmitter for the rest of the year. With this in mind
it would be most prudent to measure the cable loss accurately. to
establish the annual benchmark.

Ok.

You haven't mentioned how you intend to deal with the likely case where
VSWR1.

Considering the test equipment I have available to use in a
temperature stablized building an Agilent network analyzer or use an
old HP power meter at the top of the tower I am thinking that
measuring rho of the cable while terminated in a short may be the more
accurate way to go.

Yes, especially if the NA is calibrated against o/c, s/c and Zo locally.

If for example, you discover that the one way matched line loss is
6.75/2dB (3.375dB), and you measure the fwd and reflected power at the tx
end to be say 200W and 15W, you could use the calculator I mentioned to
determine that the VSWR at the antenna was 1.36. Using that, and setting
forward power at the antenna to 102W for a net power to the antenna of
99.6W, forward and reflected at the tx end of the line should be 222W and
1.1W.

Of course, if the line was perfectly matched, you could just set the tx
end forward power to 100*10^(3.375/10) or 217W and reflected would be
zero... but that is unlikely. You could take the easier, simpler and
conservative way out and just set it for 217W forward irrespective of
mismatch.

It is splitting hairs, but sometimes precision in the method distracts
attention from accuracy!

Owen



using the calculator I mentioned, and setting the line loss to the tx to
3.375dB, loss to antenna to 0, tx power to