[time-nuts] How does sawtooth compensation work?
kb8tq at n1k.org
Tue Jul 19 17:44:26 EDT 2016
The only way to be sure on either the sawtooth or the cable delay is to
try it and see. I have observed it being put in backwards (in both cases)
more often than I have seen it put in the right way around.
> On Jul 19, 2016, at 12:47 PM, Mark Sims <holrum at hotmail.com> wrote:
> While on the subject of antenna cable delay and sawtooth values, I have only seen Trimble document the sign of the value that you enter to compensate for cable delays (for Trimble devices you enter a negative value). Other receivers may require a positive or negative value. Also, some receivers will not accept will not accept negative cable delay values and can only move the PPS in one direction from nominal using their cable delay feature.
> Also, I have never seen anybody document how the sign of their reported sawtooth compensation value relates to the PPS edge. For some receivers it is the offset of the PPS edge from true time. For others it is the delay you need to apply to the edge to get it to true time.
> Asking the manufacturer about either value may or may not give the correct answer. The only way to know for sure is to test it... and that requires comparison to a known to be correct and very accurate PPS source...
>> The systems that use 1PPS delay chips solve your worry with an at-power-on adjustment to the receiver's antenna delay parameter.
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