I used to measure WWV carrier only (a much more pedestrian approach than yours) with a qs1r locked to a Valon synthesizer driven by a a very nice (for my budget) 1000A oscillator that Corby provided me.
I often saw (now I could be reading your data wrong) a minimal shift when the signal strength was very low. I researched this phenomenon for quite some time and my hypothesis was that this represents a point where you receive only non-Doppler shifted signal via pure reflection at the ionospher. From the papers is read this component is always received but it is buried within the usually stronger shifted components. If I remember right there is a name for that direct (non-shifted) component but it escapes me. I then moved, got busy and haven’t gotten an antenna back up. Your results make me want to get less busy again. Thanks, Bill Dailey > On Nov 27, 2018, at 7:40 PM, Scud West <[email protected]> wrote: > > I’ve been monitoring the Doppler shift of WWV/H and CHU for a while now from > my location 100 km / 60 mi NW of Seattle. > > The receiver is a QS1R, using an LTC2208 16 bit ADC, and the 125 MHz clock is > provided by a Bodnar GPSDO. A Wellbrook ALA1530S+ loop antenna provides good > coverage for the entire range. > > I use a Python script to tune the QS1R to each frequency for 11 seconds while > in CW mode. The 800 Hz beat frequency is measured using the open source > program Fldigi. > > Fldigi is mainly intended for HF digital modes like RTTY and PSK31, but the > “Frequency Analysis” function is effectively an audio frequency counter with > .001 Hz resolution, updated every 1.024 seconds. The first 5 or 6 samples > are discarded after a frequency change. The signal must be within about ± 5 > Hz. > > During many minutes, WWV transmits a 500 Hz tone, and WWVH a 600 Hz tone (or > the reverse). By treating these as separate carriers (e.g. tuning to 5.0006 > MHz) I'm able to separate the Doppler shift and signal strength of the two > stations. It's remarkable that Fldigi is able to make an accurate > measurement of the 500/600 Hz "carriers", since there is a 40 ms gap > surrounding the tick sound each second. > > I've just recently got enough of a handle on Python, Matplotlib, Pandas, > JupyterLab, and other excellent tools to even begin to analyze and display > the data. > > > From my location: > > WWV: Ft Collins, CO 1,675 km, 1,040 mi, 113° > WWVH: Kauai, HI 4,335 km, 2,694 mi, 241° > > > > > Each datapoint for the 500/600 Hz signal is plotted, to give a sense of the > signal variation. Only the smoothed carrier signal is plotted, because > otherwise it made the graph "too" busy (ha). The 500/600 Hz plots are moved > up by 15 dB to correspond with the carrier level. But this means their > displayed noise floor is raised as well. For instance, the WWVH signal from > 18:00 until past 00:00 is mostly in the noise. > > > > > Each observation is for 5 or 6 seconds, and taken a few minutes apart. If > the standard deviation of the observation exceeds 0.150 Hz it is rejected. > The reject is plotted in light gray, but otherwise ignored. That's the only > filter being applied to the data. WWV is usually stronger at my location, > and the carrier data correlates with it pretty closely. Based on looking at > a few days data, usually WWV gives a more accurate and higher confidence > reading than the carrier alone, and considerably better than WWVH. Last week > the largest daily 5 MHz WWV median was .010 Hz (2.0e-09); one other day was > .003, but most were .001 (2.0e-10). > > > I'm just now getting presentable results, and expect to find errors: > cosmetic, conceptual, and fundamental. Currently the Python script is as > shaky as my understanding of basic statistics. > > Oh well, back to the data > > > Rob > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
