Unfortunately I did not have the ability to log temperature at the time I did that test.  I just added support to Lady Heather for an environmental sensor so I should be able to do that later on.  Currently my environmental sensor code only does two channels of temperature.  I am going to build a board with an ATMEGA 328 chip and BMP280 for humidity and pressure along with support for a couple of temperature sensors (should be able to do type K thermocouples and RTD1000's)

to compare with the mw-journal plots?

Hi

On something like a 500’ spool of coax, the question will always be “what temperature is it where in the spool”. A single sensor will
only give you precise information if the temperature ramp is very slow (as in days …).

Bob

On 4/18/17 3:55 PM, Bob kb8tq wrote:

measure the DC resistance of the spool, and you'll be able to get a sort
of "average" temperature.

Hi

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 …).

Bob

On 4/19/17 3:34 AM, Bob kb8tq wrote:

One would want to calibrate your "coax as temp sensor" just in case
you've got some exotic stuff with silver plated over stainless steel
(used in cryo applications).  But you could probably do that with a
short length.

Copper is about 0.4% /degree
Iron is about 0.6%

So, over a -10 to 60 degree swing you'd see about significant (30-40%)
change in the resistance, and it would be easy to tell if it's copper or
iron or NiCr or something really exotic.

The Belden catalog says that RG58/U type coax is about 7-8 ohms/1000 ft.
So a 10 foot length is 0.07 ohms - A bit tricky to measure that low, but
not impossible, and certainly within the scope of a time-nut skilled in
the electronics arts.