Reg wrote:
"For 100 years or more, new multipair phone and other cable types have
been acceptance tested with reflection coefficient bridges. One pair in
the cable is exhaustively tested for everything the test engineer can
think of to make sure there`s nothing wrong with it.."

Why bridge test a cable pair that has continuity and accessible
terminals?

I would rather measure the transmission characteristics that I might
use.

The impedance of a 2-wire circuit may be of interest for balancing a
term-set, but that is usually accomplished by adjusting the balance
network by trial and error for the best balance or for most transhybrid
loss. Another option is to accept a compromise fallback network which
gives whatever hybrid balance results, good or bad.

One can locate a line fault by using:
wavelength = V / f

Where multiple repeaters are in a chain, as in Reg`s undersea cables,
each repeater can generate its own unique pilot tone. One can check the
tones to determine where the chain is broken. I`ve done that with
terrestrial microwave systems and recorded the tone interruptions on a
multichannel event recorder with synchronized timing marks. Whenever an
outage occurs, time, location, and duration are charted.

For a rough check on local telephone loops in the swirtched telephone
system here, the phone company had a dial-up tone oscillator in its
central offices. More significantly, other subscribers can be dialed up
to determine the quality of the connections that can be made.

Data circuits often have a loop-back capability in data modems, used to
determine error rate. This is another way to evaluate circuits.

For broadcast program lines, and other leased circuits, the phone
company will treat the line to meet specifications. The customer then
tests his own circuits to make sure he is getting what he pays for.

There are "silent" test systems for multipair cables which test with
tones outside the audible range. These can evaluate attenuation and
cross-talk and these can be related to the similar values in the audible
range.

SWR is a function of reflection strength. I see no problem in labeling a
reflection strength as SWR, even though there may not be enough cable
for a standing wave pattern. I think TLI would be a fine meter name too.

Best regards, Richard Harrison, KB5WZI

I would rather measure the transmission characteristics that I might
use.

===============================

You've never acceptance tested a 20-mile long phone cable, 542-pairs,
88mH-loaded every 2000 yards.

There are so many things which can go wrong with it you can't believe it.

For example, it is a waste of time measuring line attenuation (loss) on all
542 pairs as a means of detecting a possible imperfection in any one pair.

Very serious defects, sufficient to disrupt normal service, can be entirely
overlooked if attenuation is measured just at one or two frequencies as a
check to see if loss is between specified performance limits. Loss is so
small on transmission lines it is very difficult to measure accurately. It
can get lost in temperature changes especially on overhead lines.

I know - I've done it !

It is obvious the most sensitive of ALL measuring instruments is a bridge
used to compare one value with another, good with bad. The bad sticks out
like a sore thumb even if it is only a teeny bit bad.
---
Reg.

Where multiple repeaters are in a chain, as in Reg`s undersea cables,
each repeater can generate its own unique pilot tone. One can check the
tones to determine where the chain is broken.

==============================

How does each repeater generate its unique pilot tone when a trawler or
earthquake breaks the inner conductor. Or do you have another way of
powering repeaters at the bottom of mid-atlantic?

Reg, G4FGQ

One can locate a line fault by using:
wavelength = V / f

=====================

How do you manage at the lower frequencies when velocity is a function of
frequency ?
---
Reg

On Tue, 16 Sep 2003 01:02:49 +0000 (UTC), "Reg Edwards"
wrote:

One can locate a line fault by using:
wavelength = V / f

=====================

How do you manage at the lower frequencies when velocity is a function of
frequency ?
---
Reg


Inventing new problems? Old wine in new bottles more like it ;-)

The velocity to the nearest geo-synchronous satellite is close enough
to constant that it doesn't matter. One repeating station and it is
quite obvious when it is dead (solves the parking problem for the next
one to replace it too).

GEOS too far away? Use LEOS instead and talk around the dead one
(it's going to fall into the sea/Australia/China/Canada anyway).

And for those still in love with wire are promises from nanotechnology
to tether satellites to earth in the future (power generation for
cheap - life expectancy for the guy that throws the switch is nil
however).

73's
Richard Clark, KB7QHC

On Mon, 15 Sep 2003 22:42:00 -0500, Cecil Moore
wrote:

Chipman never said the reflected power can be greater than the forward power
into a passive load.

Hi Cecil,

You are the only one to just have suggested he did. Others (in total
wide-eyed innocence) may have drawn that faulty conclusion by
inference, but they also have missed the boat on many other issues.

73's
Richard Clark, KB7QHC

I would like to emphasize that
the Uniform Transmission Line Theory valid relation

|Xo/Ro| = 1

is _not_ used
in any step in the proof of

R(l) = Rt = 0.

This is obvious
from the derivation
in the referenced thread.

Sincerely,

pez
SV7BAX

On Tue, 16 Sep 2003 10:06:52 -0500, Cecil Moore
wrote:

Richard Clark wrote:

wrote:
Chipman never said the reflected power can be greater than the forward power
into a passive load.

You are the only one to just have suggested he did.

Because of a death in the family, I entered the discussion late, but
I thought that was what Roy was asserting using his calculations,
that fP - rP was a negative value.

Hi Cecil,

Then you should respond to that posting. The reason for this
suggestion is that you now continue to make speculative assertions
pegged against two names in a discussion where you are admittedly in
the dark.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
Then you should respond to that posting. The reason for this
suggestion is that you now continue to make speculative assertions
pegged against two names in a discussion where you are admittedly in
the dark.

Richard, why are you trying to hold me to a higher standard than to
which you hold yourself?
--
73, Cecil http://www.qsl.net/w5dxp



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On Tue, 16 Sep 2003 12:36:56 -0500, Cecil Moore
wrote:

Richard Clark wrote:
Then you should respond to that posting. The reason for this
suggestion is that you now continue to make speculative assertions
pegged against two names in a discussion where you are admittedly in
the dark.

Richard, why are you trying to hold me to a higher standard than to
which you hold yourself?

Hi Cecil,

So, is your interest in pursuing unrelated matters here, or posting to
the original technical discussion you can only guess at?

When I offered discussion employing Chipman's comments, I posted them
to those who showed interest, to those who showed they were versed
with the author, to those who showed inquiry into his credentials,
to those who showed ignorance to his specific limitations of requiring
the source Z to match the line and a host of other specifics all
offered in direct response unlike you. I can tell you who has a copy
available, who has shown interest in obtaining a copy, who has a copy
in transit from an Australian vendor, and who has asked about the
author as being a former instructor of theirs. And none of these
individuals has yet to respond to simple but necessary observations by
Chipman of the requirement of the Source Z. Do you join that throng?

If these low standards have the bar set to high for you....

73's
Richard Clark, KB7QHC