[time-nuts] Cable length calibration

[Scott McGrath]

This is highly dependent on the TDR especially ones designed for long twisted pair runs where a high voltage pulse is used to overcome resistive losses

Content by Scott
Typos by Siri

> On Jun 30, 2016, at 10:59 AM, David <davidwhess at gmail.com> wrote:
> 
> The Tektronix 1502 uses a tunnel diode pulser to produce a 50
> picosecond output step of about 200 millivolts.  There is a misprint
> in the theory section of the service manual which says "400 V" instead
> of "400mV".
> 
>> On Thu, 30 Jun 2016 04:19:43 -0400, you wrote:
>> 
>> If the nominal velocity of propagation is known and length is known delay is easily determined mathematically 
>> 
>> Time Domain Reflectrometry is the usual technique for finding cable length but even there the cables NVP is an essential parameter if you want to compute length but not essential in time nuts application because we are interested in delay which a TDR reads directly When using a TDR its best if cable is unterminated as the discontinuity at the end is helpful as a marker.   Also most TDRs like the Tek 1502 can put 100v or more on the cable which will blow most GPS antennas
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