Jimmie D wrote:
I need to measure the loss of aproximately 200ft of coax @ a freq of 1Ghz.
The normal procedure for doing this is to inject a signal at one end and
measure the power out at the other. Using available test eqipment this is a
real pain to do. I propose to disconnect the cable at the top of the tower
terminating it in either a short or open and measure the return loss at the
source end. I have done this and measured 6.75 db and I am assuming that 1/2
of this would be the actual loss of the cable. These numbers do fall within
the established norms for this cable. Can you think of a reason thiis method
would not be valid?

Sounds right...

Send the signal up, have a loss of 3.375 dB, all of it reflects back
from either short or open, another 3.375 dB loss, so the reflected
signal is down 6.75dB.


If you wanted to get real fancy, you could terminate in a known mismatch
too..

But that's getting up towards doing port cals on a VNA.

I assume you're not looking for tenth of a dB precision?

Jim