[time-nuts] Cable length calibration

[Scott McGrath]

I'd say it depends on the Time Nut 😀.  NVP X Distance will get you close and for a beginning time nut is a worthwhile exercise 

To improve delay calculations now you need instrumentation that not all especially beginning time nuts own.    I've got a 20 Ghz Agilent scope/TDR along with a 110 Ghz network analyzer and just putting a cable on the network analyzer and handling it you can see the characteristics change    So yes you are correct that the simple NVPxDistance is not suitable for advanced time nuttery.   In fact the delay will change with temperature and barometric pressure unless you are using hardline and that's subject to humidity unless filled with dry nitrogen under pressure.

Content by Scott
Typos by Siri

> On Jun 30, 2016, at 5:03 PM, Dr. David Kirkby (Kirkby Microwave Ltd) <drkirkby at kirkbymicrowave.co.uk> wrote:
> 
>> On 30 June 2016 at 09:19, Scott McGrath <scmcgrath at gmail.com> wrote:
>> 
>> If the nominal velocity of propagation is known and length is known delay
>> is easily determined mathematically
> 
> Except that coax does not have a uniform impedance or velocity factor. Both
> will vary as a function of position and frequency. How relevant this is
> depends on the accuracy you require, but since it is time-nuts, it is
> reasonable to assume that such a simplistic method is not of the standard
> expected on time-nuts.
> 
> Dave
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