On 11/26/2014 10:11 PM, Jim Brown wrote:
How far down were the harmonics? -40 is 1% distortion, -50 is 0.32%. 5% is widely considered to be "communications quality."
The tones [500 and 600 Hz on alternate minutes] are transmitted at 50% modulation. The second harmonic of the tone on 10 MHz is about 15 to 18 dB below the fundamental tone on my P3 using the dBm scale. There is selective fading visible on the tones. The third harmonic is roughly another 15 dB below the second harmonic, and it fades more. At times, I can discern the fourth harmonic on the waterfall in monochrome mode, but can't see it on the spectrum display.
The tone fundamental and each of the harmonics are surrounded by the sidebands of the 100 Hz sub-carrier and the IRIG-H time code.
The striking part for me is the difference between 2.5/20 MHz and the other three. 2.5/20 are very clean, no tone harmonics, and the 100 Hz sub-carrier is where it should be and nowhere else.
When I've listened to WWV (not often), I hear distortion. They're a Standard for Frequency and Time, not high futility. :)
The modulation that is generated at Ft. Collins [tones, ticks, time announcements] appears to be very high quality and exact. The weather, GPS status, and propagation announcements seem to come from other places and are of highly variable quality, mostly unintelligible for me.
The WWV time announcements are rumored to be the voice of San Francisco area radio announcer. This may be an urban legend however. :-)
73, Fred K6DGW - Northern California Contest Club - CU in the 50th Running of the Cal QSO Party 3-4 Oct 2015 - www.cqp.org ______________________________________________________________ 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
