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.
--

With all due respect, that's a rather frightening position to maintain.
I've had to replace both .750 and .500 because of dings. Complaints were
that certain channels were out. A couple of years ago I had to replace a 4
foot piece of RG 6 inside a wall (splitter to outlet) that had the
attenuation of a 100 foot cable. 950MHz to 1450MHz worked (though not near
as well as it should have), but the rest of the bandwidth up to 2200MHz
didn't work at all. Electricians had greatly exceeded the minimum bend
radius when they made up the outlet.

DC does not necessarily mean that RF will work, nor does RF necessarily mean
that DC will work.

--

CIAO!

Ed N.


"Ian Jackson" wrote in message
...
years. I have found that, if it buzzes out OK at DC, it will generally be
OK at RF.
Ian.
--

In message , Ed Nielsen
writes

"Ian Jackson" wrote in
message ...
years. I have found that, if it buzzes out OK at DC, it will
generally be
OK at RF.
Ian.

With all due respect, that's a rather frightening position to maintain.
I've had to replace both .750 and .500 because of dings. Complaints
were that certain channels were out. A couple of years ago I had to
replace a 4 foot piece of RG 6 inside a wall (splitter to outlet) that
had the attenuation of a 100 foot cable. 950MHz to 1450MHz worked
(though not near as well as it should have), but the rest of the
bandwidth up to 2200MHz didn't work at all. Electricians had greatly
exceeded the minimum bend radius when they made up the outlet.

DC does not necessarily mean that RF will work, nor does RF necessarily
mean that DC will work.


Ed, I'm sure what you say is true. However, one-off moderate mismatches
(or even repeated moderate mismatches which are buffered by
attenuation), such as might be caused by the use of poor quality
connectors, should not cause a failure of service unless the service
would have been marginal if the connectors were good.

As for bends in cable, if you can, tie a loose knot in a piece of coax,
run a wideband sweep through it, and observe the output. Now pull the
knot tight. Let me know when the output starts to be affected.

Let me say again, I'm not advocating sloppy practices and poor
workmanship. Manufacturers' specs and industry standards should always
be adhered to. This avoids endless truck-rolls (God - I hate that
Americanism!) to the 1% of customers where some bright spark has cut one
corner too many. But, especially in the amateur world, we should maybe
not worry too much about using things which industry has rejected, often
for reasons which have absolutely no impact on what we are trying to do.
So I'm NOT throwing out my stash of crimp and screw-on F-connectors!

Ian.
--

Let's just agree to disagree. We both hold positions based, at least in
part, on many years of experiences.

I did not say that hex-crimp fittings WILL cause issues, I said they COULD
cause issues.

As for the knot/sweep thing; no need. I have already seen the results.

--

CIAO!

Ed N.


"Ian Jackson" wrote in message
...
In message , Ed Nielsen
writes

"Ian Jackson" wrote in message
...
years. I have found that, if it buzzes out OK at DC, it will
generally be
OK at RF.
Ian.

With all due respect, that's a rather frightening position to maintain.
I've had to replace both .750 and .500 because of dings. Complaints were
that certain channels were out. A couple of years ago I had to replace a
4 foot piece of RG 6 inside a wall (splitter to outlet) that had the
attenuation of a 100 foot cable. 950MHz to 1450MHz worked (though not
near as well as it should have), but the rest of the bandwidth up to
2200MHz didn't work at all. Electricians had greatly exceeded the minimum
bend radius when they made up the outlet.

DC does not necessarily mean that RF will work, nor does RF necessarily
mean that DC will work.


Ed, I'm sure what you say is true. However, one-off moderate mismatches
(or even repeated moderate mismatches which are buffered by attenuation),
such as might be caused by the use of poor quality connectors, should not
cause a failure of service unless the service would have been marginal if
the connectors were good.

As for bends in cable, if you can, tie a loose knot in a piece of coax,
run a wideband sweep through it, and observe the output. Now pull the knot
tight. Let me know when the output starts to be affected.

Let me say again, I'm not advocating sloppy practices and poor
workmanship. Manufacturers' specs and industry standards should always be
adhered to. This avoids endless truck-rolls (God - I hate that
Americanism!) to the 1% of customers where some bright spark has cut one
corner too many. But, especially in the amateur world, we should maybe not
worry too much about using things which industry has rejected, often for
reasons which have absolutely no impact on what we are trying to do. So
I'm NOT throwing out my stash of crimp and screw-on F-connectors!

Ian.
--