In message , Roy Lewallen
writes
Ed Nielsen wrote:
At a trade show several years ago, a vendor demonstrated the effects
stapling cables could have on signal transmission. He took a VCR, a
ch. 3 modulator and a piece of drop cable and attached the cable to a
piece of wood utilizing a regular staple gun that you buy at any home
improvement store. Used the gun as most people would, and inspection
of the cable showed it to be fine (undamaged). By the seventeenth
staple, ch. 3 was completely gone..
It doesn't take major crushing to create mismatch, and as to whether
it is significant sort of depends on what happens to be trying to get
through at the particular point where the mismatch occurs.

A periodically repeating mismatch, such as the one produced by the
staple demonstration, can cause extreme effects as the demonstration
showed. This is a very much worse case than a single mismatch.

Roy Lewallen, W7EL

Stapling - or any other small mismatch repeated at regular intervals -
can indeed produce a severe structural mismatch (with the associated
suckout) at frequencies where the intervals are one wavelength, and
multiples thereof. However, the presence of a one-off connector where
the match is distinctly questionable will usually go completely
un-noticed (except to the most discerning of engineers). I still
maintain that any problem will be because there is no proper continuity
through the connector, or possibly an inner-to-outer short (maybe
partial). I must admit, I haven't used an RF TDR in earnest for over 20
years. I have found that, if it buzzes out OK at DC, it will generally
be OK at RF.
Ian.
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