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 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
