[hpsdr] Internet NTP useful for Ham freq measurement?

[Dan Mills]

On Mon, 2012-10-15 at 12:05 -0400, John Ackermann N8UR wrote:

> You could set something up that uses a good quality OCXO locally that 
> gets steered once a day or so to NTP, but I think you'd spend more and 
> get worse performance than other options.

Actually NTP is quite useful for ham stuff, not so much as a frequency
reference but as a way to get relatively accurate time without going to
the extremes of something like a TBolt GPS timing rx. 

Some of the weak signal modes rely on the time at the transmitter and
receiver being synchronised to within a few seconds, and NTP is more
then man enough for this use. 

I don't know about Windows, but the Linux kernel actually locks a
software PLL to the NTP reference and uses this rather then the RTC on
the motherboard for wall clock time, it is not a case of comparing every
hour or so and jam synching at that point, but of actually doing a long
loop timeconstant PLL in software. 

man adjtimex(8) has some interesting comments, and the kernel
timekeeping code is some very clever stuff. 
 
Regards, Dan.


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