Bob wrote:
On Tue, 06 Apr 2010 01:26:16 GMT, Owen Duffy wrote:

Bob wrote in
:

On Tue, 06 Apr 2010 00:16:56 GMT, Owen Duffy wrote:
...
I have had sucess with placing a balun of a string of ferrite cores
over the line.
That means literally threading some suitable ferrite toroidal cores over
the transmission line you are measuring.

If you add a separate balun between the analyser and the cable under test,
you introduce an unknown component that will probably disturb your
readings.

Owen

Another question -- I'm thinking of cutting a 10-foot section of
balanced line to test. Should I count the bared pigtails of the line,
which I will attach to the analyzer's coax output, as part of the 10
foot length? Or just count that part of the line where all insulation
is in place?


Aha.. you start to see the problems in precision RF measurement... Where
is the "reference plane"..and how do you calibrate out the "fixture".

One way to do it is to do two sets of measurements. Do one with your 10
foot length. Then, cut 5 feet off and do it again. Then, the
"difference" between the measurements is the result for the now missing
5 feet.

How much precision are you looking for, anyway. To a first order, think
about how long that fixture is. If it's an inch or so, that's less than
1% of the overall length of the line.