[Elecraft] OT: Changes at WWV, WWVB

[dave]

A minor point . . . but I believe that the GPS satellites carry 
rubidium standards, not cesium. IIRC, the rubidium standards are much 
smaller and lighter and much more suited to satellite use.

At one time I used a cesium standard to troubleshoot a timing issue 
when clocking the phone network. I think it, in its shipping 
container, weighed about 75#. The container probably weighed less than 
15#. A cesium standard is fairly heavy. We had to lug it up to the 3rd 
floor of one central office.

But the rubidium standards in the satellites are synced to the earth 
mounted cesium standards each day. And rubidium standards actually 
have better short term stability than do cesium standards. At least 
that is what I was taught in the various timing classes I attended.

73 de dave
ab9ca/4



On 11/28/14 2:18 PM, Ken G Kopp wrote:
> I have a long-time close friend who's retired from
> the NBS in Boulder and was the project engineer
> on the NBS #7 cesium standard.  After the recent
> reflector postings about  WWV / WWVB I thought
> I would get first-hand recent information from him.
>
> The GPS satellites all carry on-board cesium
> standards that are synchronized with NTIS, and
> because of changes (below) to WWVB, cell phones
> remain the most accurate source of time for most of us.
>
> All the HF transmitters at Ft. Collins are the same TMC
> units that were put in service when the facility was built.
> The 2.5 and 20 MHz transmitters run at lower power due
> to propagation considerations.
>
> The time and other station-related voice info is sourced
> on site in Ft. Collins, and the various propagation and
> weather info comes from various "dial in" land-line
> sources. Hence the widely varying quality of these
> announcements.  I forgot to ask about the individual
> who made the voice recordings ...
>
> Here's the most important info .... as of about a year
> ago the modulation scheme on WWVB (60 kHz) was
> changed (phase reversal each minute) and this has
> rendered most of the end-user equipment inoperative.
> Most (all ?) tracking receivers like the HP-117's are
> now useless without extensive modification.
>
> Most of the "atomic" clocks now in use ->do not<- synch
> to the current modulation scheme on the 60 kHz signal.
> This will explain the differences in displayed time on
> supposedly identical clocks and how some appear to
> not be getting sufficient enough signal to synchronize.
>
> He offered no comment on how to locate "consumer"
> clocks that -do- respond to the "new" modulation scheme.
>
> The 60 kHz transmitter is indeed an ex-LORAN C unit,
> and because of the higher power of the "new" transmitter
> the antenna system was rebuilt using material from the
> LORAN C site.
>
> The 20 kHz transmitter was "home made" by NBS staff
> at the old Beltsville, MD facility and moved to Ft. Collins.
> There is no longer an antenna for this transmitter and it
> will not return to the air.  Trivia:  The antenna was of
> such high-Q that a near-by thunderstorm system would
> often detune the system and cause the overload protection
> to trip the transmitter off.
>
> He suggests that a visit to the NBS website would be
> "informative".
>
> 73
>
> Ken Kopp - K0PP
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