I finally got around to using a TICC to measure the temperature coefficient of 100 feet of generic RG-58 coax using a TICC. The TICC was clocked by a HP 5071A 10 MHz output. The 1PPS output was connected to the input of the coax and the TICC chB input. The TICC chA input was connected to the coax output via an inline terminator. The TICC was set to "debug" mode and Lady Heather plotted the chB-chA timestamp difference (hence the negative cable delay values). The coax had been chilled down for 2 hours in a 5 degrees F in a freezer, connected to the TICC, and left to warm up in a 75 degree F room. Over the 10F to 70F temperature range (measured with an IR thermometer) the coax delay spanned around 300 ps... so figure around 5 ps per degree F (10 ps per degree C) for 100 feet of cable. I'm adding currently adding the ability for Heather to use an external temperature sensor...

The recent supplement to Microwave journal has a piece on phase stability of cables (predictably - written by a vendor of said cables..): http://www.microwavejournal.com/publications/1/editions/223 maybe you can recalculate your results in PPM and plot against temperature, to compare with the mw-journal plots? Anders On Sat, Apr 15, 2017 at 4:34 AM, Mark Sims <holrum@hotmail.com> wrote: > I finally got around to using a TICC to measure the temperature > coefficient of 100 feet of generic RG-58 coax using a TICC. The TICC was > clocked by a HP 5071A 10 MHz output. The 1PPS output was connected to the > input of the coax and the TICC chB input. The TICC chA input was connected > to the coax output via an inline terminator. The TICC was set to "debug" > mode and Lady Heather plotted the chB-chA timestamp difference (hence the > negative cable delay values). > > The coax had been chilled down for 2 hours in a 5 degrees F in a freezer, > connected to the TICC, and left to warm up in a 75 degree F room. Over > the 10F to 70F temperature range (measured with an IR thermometer) the coax > delay spanned around 300 ps... so figure around 5 ps per degree F (10 ps > per degree C) for 100 feet of cable. > > I'm adding currently adding the ability for Heather to use an external > temperature sensor... > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. >

On 15 April 2017 at 02:34, Mark Sims <holrum@hotmail.com> wrote: > I finally got around to using a TICC to measure the temperature > coefficient of 100 feet of generic RG-58 coax using a TICC. The TICC was > clocked by a HP 5071A 10 MHz output. The 1PPS output was connected to the > input of the coax and the TICC chB input. The TICC chA input was connected > to the coax output via an inline terminator. The TICC was set to "debug" > mode and Lady Heather plotted the chB-chA timestamp difference (hence the > negative cable delay values). > > The coax had been chilled down for 2 hours in a 5 degrees F in a freezer, > connected to the TICC, and left to warm up in a 75 degree F room. Over > the 10F to 70F temperature range (measured with an IR thermometer) the coax > delay spanned around 300 ps... so figure around 5 ps per degree F (10 ps > per degree C) for 100 feet of cable. > > I'm adding currently adding the ability for Heather to use an external > temperature sensor... > I would not assume that a reel of coax that is coiled up will behave the same as when used in in a lab environment in the usual way. So whilst this might be an interesting experiment, I believe some caution would need to be applied before assuming that such a measurement is representative of how coax is normally used. When not on a reel, a heated coax is free to expand radially with no external pressure force applied, apart from that due to air pressure. When on a reel, that's not the case, as the coax is the middle of the reel is going to have forces applied that are much greater due to the mass of the coax. To take an extreme example, if you use a foam dielectric coax, when on a real, the airgaps in the foam are likely to become smaller as the cable will experience mechanical forces as it tries to expand, constrained by the coax around it. Also, when the coax tries to expand under heat, it is likely to deform to take up the space between the turns on the reel, so possibly become more square. Unfortunately cable is likely to behave very differently at 10 MHz than 10 GHz, so it not necessarily useful to repeat a measurement with a small piece of coax at 10 GHz, where its phase change could easily be measured on a vector network analyzer. Another spanner in the works is that the impedance of coax (usually 50 Ohms), is given by the equation Z=sqrt( (R + 2 pi f L)/(G + 2 Pi f C) ) where R is the resistance per unit length, L is the inductance per unit length, G is the conductance per unit length and C is the capacitance per unit length. The high frequency approximation is that 2 pi f L >> R, and 2 Pi f C >> G, so it simplifies to sqrt(L/C). Those two assumptions become less valid at low frequencies. Overall, what you are doing seems interesting, but I would question how much the results will relate to real-world use of coax, where its not normal to have great real of it. Dr. David Kirkby Ph.D CEng MIET Kirkby Microwave Ltd Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT, UK. Registered in England and Wales, company number 08914892. http://www.kirkbymicrowave.co.uk/ Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please)