Olin Lathrop wrote:

> Howard Winter wrote:
> 
>>That rather depends where you are in relation to the tramsmitter -
>>I'm about a hundred miles from the MSF 60kHz transmitter in Rugby
>>(Midlands of England) and I have several clocks that receive it
>>reliably, and believe me, my house has *lots* of electrical
>>interference in it! :-)  And as I understand it low frequency signals
>>normally travel by Ground Wave, so shouldn't be affected by diurnal
>>variations.
> 
> 
> This isn't a problem when you're on the same small island as the
> transmitter.  100 miles is quite close.  I'm about 2000 miles from WWVB in
> Boulder Colorado.  Around here clocks only synchronize at night.

http://www.boulder.nist.gov/timefreq/stations/wwvb.htm

Olin,
http://www.boulder.nist.gov/timefreq/stations/wwvbcoverage.htm
cleary shows that the coverage area varies with time of day.
" Note that the coverage area contracts during daylight hours
and expands during nighttime hours."

http://www.boulder.nist.gov/timefreq/general/pdf/1976.pdf
"WWVB Radio Controlled Clocks:
Recommended Practices for Manufacturers and Consumers"
has a good discussion for design of consumer radio clocks
and a table of VLF time broadcasters.

Robert

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