Use the highest freq WWV signal you can get good reception on, and be certain that you do it during one of the no audio periods. All WWV's are not created equal either. The 2.5 and 20 MHz show an expected spectrum of carrier plus either 500 or 600 Hz sidebands, and the 100 Hz IRIG-H timecode subcarrier right around the main carrier. It appears that these two transmitters use low level modulation and highly linear amplifiers. 5, 10, and 15 MHz use the same modulation stream but are high level modulated class-C PA's. If you look at their spectra, you will see fairly strong harmonics of the 500/600 Hz tones, and the tones and all the harmonics will be modulated with the 100 Hz IRIG-H time code. So far as I can determine, all the WWV frequencies start out at 10^-12 or better.
73, Fred K6DGW On 8/21/2012 7:53 PM, Jack Smith wrote: > As transmitted, frequency error is less than 1 part in 10 to the -12th. > > As received, due to Doppler error and other ionospheric issues, and > depending on how you go about the measuring process, something like 0.1 > PPM is about it. Maybe a hair better if you have excellent propagation > and you go about the comparison process correctly. Maybe 1 PPM > off-the-air if you are doing a quick and dirty comparison, such as > watching the S-meter swing around. > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
