[Elecraft] Re: WWV DST

[John Magliacane]

Hi Mark.

> Thanks for the reference. However, the idea that this system is
> 'superior' would depend upon why one is looking for a time reference.
> If all you want is a relatively high accuracy clock the WWV signal is
> superior IMO. It certainly is easier to decode! As an added benefit it
> includes the DST bit -- you never know when the govt will decide to
> change the DST rules.

Very true, but compared against WWVB and GPS, WWV/WWVH/CHU reception achieves
the poorest accuracy as a time and frequency reference due to the inherent
variability of ionospheric propagation.

NIST claims WWV/WWVH time reception to be accurate to within 1 to 20 ms.
WWVB reception is accurate to within 0.1 to 15 ms.

NIST's Frequency Measurement and Analysis Service, which is GPS-based, is
accurate to within 20 nanoseconds.  This precision is due in part to the fact
that NIST itself monitors the GPS signals while FMAS measurements are made, and
so the readings taken are, in fact, traceable to NIST's atomic standards.

Obviously, this is well beyond the accuracy most hams need in their shacks, but
modern soundcard based weak signal and SSTV modes are demonstrating very
clearly the increasing importance of being able to send and receive highly
accurate, stable, and well timed signals.  I suspect that trend will continue.


73, de John, KD2BD


Visit John on the Web at:

	http://kd2bd.ham.org/
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