Here's my take on this.
Unfortunately coax has to really bad to tell that it is with the usual
instruments available to most of us.
One is generally trying to measure losses in the <1 to maybe 1.5 db
range. The uncertainties overwhelm the 0.5 db difference that
constitutes lossy vs nominal loss.
I once tried using a 50 ohm signal generator and dummy load at the far
end. It turns out if one "sweeps" frequency there are cyclic increases
and decreases in loss due to the usually available voltage sampling
devices impact and the residual dummy load mismatches/complex impedance
components. No matter what I tried, I could not get rid of what I think
were standing waves. Experiment a failure.
So if you suspect coax is old and possibly lossy, stick it on 160 or 80M
and buy new stuff.
73 de Brian/K3KO
On 9/14/2012 18:01, Wilson Lamb wrote:
After all the recent talk about losses and switchboxes, you know how to test by
simply leaving the far end open and measuring SWR.
Use your xcvr as a source and test at your operating freq.
The dummy load is a fine power test, but not a good loss test, unless you
carefully measure power at both ends
Wilson
W4BOH
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