[time-nuts] Spectracom 8161 "Standard Frequency Receiver - Oscillator" for WWVB (and question...)

[Bob kb8tq]

Hi

The height of the ionosphere changes night to day. That changes the effective
propagation distance. As the day/night (or night/day) transition point crosses the
path between you and WWVB the two “modes” compete with each other. They
can do fun stuff like cancel out the signal entirely. 

If you watch the 60 KHz on a ’scope as all this goes on, the “slip” is enough to 
make it unclear which edge is which. ( = it slips a large fraction of / more than one 
cycle). At 60 KHz, one cycle of slip gets you 16.7 us.

Indeed, just how much trouble you have depends a lot on where you are. In downtown
Ft Collins, I doubt you see much slip at all :). Here on the east coast, you see cycles. 
Even back in Kansas things got pretty crazy and that’s not a super long path sort of thing.

Our normal approach with WWVB was to check it at some specific time of day. You only
“used” the data after it had made sense for at least three days running. For anything 
important,  the target was five days running. 

Loran-C was a better alternative back then, if keeping your reference on frequency 
was the objective. Even with Loran, I would typically use more than one day’s worth of
observations ….

Bob

> On Oct 5, 2020, at 5:20 AM, Hal Murray <hmurray at megapathdsl.net> wrote:
> 
> 
>> On a WWVB setup you get 10’s of us ( yes microseconds) of movement at
>> sunrise and sunset. You get as much as 10us between day and night. 
> 
> Somehow, I was thinking that WWVB was ground wave and wouldn't be effected by 
> changes in the height of the ionosphere.  Am I totally out of it, or is 10s of 
> uSec just a lot better than the day/night shift you get with WWV?
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
> 
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