[BC] "VSWR" Metering

[Richard Fry]

Alan Alsobrook:
>When sweeping a line that is terminated into a precision load
>you want to sweep as wide as possible as this will show
>problems more clearly.
________

None of the following is news to you, Alan, but wide sweeps also can show 
"problems" that are not problems at all for the operation of the system 
under test.

For example, swept return loss measurements of a terminated, long run of 
some types of rigid coax line will show high returns in various parts of 
the spectrum due to the accumulated reflections from each flange.  Section 
lengths really need to be selected with that in mind, because one of those 
spikes might happen to fall in or near your channel.  But if they don't, 
they won't affect the performance of that particular antenna system, and 
don't indicate any kind of problem that needs to be fixed.

As with all things, training, experience and good judgment are needed -- no 
matter how good or mediocre the test equipment in use.   A veteran r-f guy 
can make a TDR out of a simple scope, and a short video pulse through a BNC 
tee that will work just fine to locate the distance down the transmission 
line to almost any fault worth worrying about.   It's the result that 
counts.

RF