[time-nuts] Measuring coax temperature coefficient with a TICC

Alan Melia alan.melia at btinternet.com
Wed Apr 19 19:11:45 EDT 2017

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??


----- Original Message ----- 
From: "jimlux" <jimlux at earthlink.net>
To: <time-nuts at febo.com>
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:
>> kb8tq at n1k.org 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 -- time-nuts at febo.com
> To unsubscribe, go to 
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there. 

More information about the time-nuts mailing list