Came across a website where they tested long cables by the
TDR method .. which sends a pulse down the cable...
Check out..
http://iti.acns.nwu.edu/pubs/cable.html
Effects of Multiple Crimps and Cable Length on Reflection Signatures
from Long Cables
The accuracy of time domain reflectometry (TDR) measurements of rock
shearing with cable lengths greater than 60 m has not been adequately
documented. This paper presents the results of controlled crimping and
shearing of a 530 m long, 22.2 mm diameter coaxial cable for comparison
with theory and the existing data from cables up to 60 m long. Effects
of both single and multiple deformities along transmission lengths of
94, 268, and 530 m were investigated. The Northwestern University TDR
Signature Analysis (NUTSA) program was employed to track and analyze
reflection spikes in the waveforms produced by controlled deformation.
The results show that pulse attenuation has a significant effect on
signal reflections. Reflection amplitudes were reduced by 500% as cable
length increased from 94 m to 268 m. Signal reflections produced by
downstream deformations are slightly decreased (amplitude reduction < )
when single or multiple deformations are applied upstream on the cable.
Deformation-reflection relationships can be characterized as bi-linear
or exponential, and show that shear deformation can be effectively
correlated with TDR reflection amplitude at distances up to 268 m.
Also.. This brings to mind an experiment to generate Plasma from a
linear amp running at 220MHz. (about 120Watts). This was done
by using a copper tube POLISHED inside with a suspended center
conductor, and matched impedance input.. with a standing wave inside.
In transmission lines, there is an equation (can't rememver off the
top of my head) that will give impedance at the end of a trasmission
line and you want the INFINITE impedance at the end. When it transmits
at the matched inpedance end.. the opposite end has +>1MV and ARC's
like you will not even believe! RF arcing too. Awsome! However
it was a pain to polish the inside of the coax. The arc was bluish
white!
v/r Ken Carrigan
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