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" <[email protected]>
To: <[email protected]>
Sent: Wednesday, April 19, 2017 11:17 PM
Subject: Re: [time-nuts] Measuring coax temperature coefficient with a TICC
On 4/19/17 11:57 AM, Hal Murray wrote:
[email protected] said:
I’d want to be pretty sure what the center conductor was made out of.
I’ve
seen some stuff in coax that “one would think†should not be there
(copper
over steel …).
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?
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.
_______________________________________________
time-nuts mailing list -- [email protected]
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- [email protected]
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
