kb8tq@n1k.org said:

Does that effect the propagation time?

If I gave you a good scope picture of a pulse after going through chunk of
coax, could you figure out the ratio of copper to steel?  Would you need to
know the length or could you figure that out too?

--
These are my opinions.  I hate spam.

On 4/19/17 11:57 AM, Hal Murray wrote:

This being timenuts, I think you might do it with just timing measurements.

Let's see - the different candidate materials all have different thermal
resistance coefficients.  So you can make some DC measurements.  If you
knew it was some combination of copper and steel, for instance, you
could probably determine the ratio from that alone (or, for that matter,
doing it at a single temperature, if you can measure the diameter of
the conductor).

There is some variation in material properties (not all copper is the
same, and, in particular, steel varies widely depending on alloy and
manufacturing).

The propagation equation has a dependence on both R and G as well as  L
and C

Is the change in prop speed due to the change in R bigger or smaller
than the change due to L and C (from dimensional changes)?

The L and C terms both have a frequency dependent (linear in frequency)
term.  The R term has a fairly complex dependency on frequency, in terms
of skin depth relative to the diameter of the conductor.  The G term
also has a frequency dependence.

TV co-ax these days for satellite or UHF is almost all steel wire with
copper plating.  In fact the 'F' connector that is used is designed to
use that stiff wire as the center pin of the connector!

Will

On 04/20/2017 06:57 AM, Hal Murray wrote:

MMmm interesting but what about skindepth ?? surely the "R" is not DC R so
would it matter? RF currents travelling in the copper anyway.  I suspect
that a steel inner might increase the L/unit length?, maybe this is more
significant or not as is sceened by copper??

Alan
G3NYK

----- Original Message -----
From: "jimlux" jimlux@earthlink.net
To: time-nuts@febo.com
Sent: Wednesday, April 19, 2017 11:17 PM
Subject: Re: [time-nuts] Measuring coax temperature coefficient with a TICC

Hi

The issue is skin depth. On something like TV coax operated at the normal
frequencies, a copper jacket is likely as good as full coper. The skin depth is such
that the signals never “see” the iron core to any real extent.

With a pulse that has a fast edge things are quite so cut and dried. Most of the
“signal” that you are measuring in that fast rising edge is at high frequencies. That
would suggest that the skin depth stuff would get you there as well.

Best way to do it would be at low frequencies either DC or a LF sine wave.

Bob

A table of a bunch of rg6 catv permutations,
http://www.texcan.com/media/import/pdf/Electronic_Cable_RG6_RG59.pdf

At least on this list if it has a solid copper core, it also has a copper
braid shield. I'm sure there is many more permutations out there.

On Wed, Apr 19, 2017 at 7:00 PM Will Kimber zl1tao@gmx.com wrote:

most likely the cooper is much ticker than the penetration of the lowest
frequency for which the cable is used, therefore the high frequency
"does not" see the steel inside of the cooper, that steel could cause
problem if the coax also used to carry some power -- DC or AC -- because
at lower frequency or DC the cable's current carried mostly in the
cooper, and while the cooper constitute just a small fraction of the
center wire cross section, a cable with "steel core" could carry much
less current, than a cable with full cooper. But the steel core cable
has one advantage it is usually stronger than a full cooper cable and
therefore it is usable for outside installation with larger support
distance.

73
KJ6UHN,  [a former engineer of a cable manufacturer ]
Alex

On 4/19/2017 11:57 AM, Hal Murray wrote: