Just listen on HfF or example about 17m (18MHz) , with a wide band digital receiver with a waterfall display. If the band is open at all, you will see them sweeping up every few minutes.
Lester B Veenstra K1YCM MØYCM W8YCM 6Y6Y les...@veenstras.com 452 Stable Ln (HC84 RFD USPS Mail) Keyser WV 26726 GPS: 39.336826 N 78.982287 W (Google) GPS: 39.33682 N 78.9823741 W (GPSDO) Telephones: Home: +1-304-289-6057 US cell +1-304-790-9192 Jamaica cell: +1-876-456-8898 -----Original Message----- From: time-nuts [mailto:time-nuts-boun...@lists.febo.com] On Behalf Of jimlux Sent: Wednesday, August 05, 2020 6:45 PM To: Discussion of precise time and frequency measurement Subject: [time-nuts] another source of time... I was researching potential calibration sources for our orbiting receivers (where we need to line up GNSS signals with HF signals) and after looking at the usual suspects like WWV, we came across another one. Ionosondes - they're all over the place, and these days, they're fairly accurately timed (how accurately? I don't know.) Timing wise, since wide band and oblique sounders are popular, they must be fairly well controlled, since the transmitter and receiver are not co-located. A traditional vertical sounder drives the transmitter and receiver off the same clock, so they don't care so much about what time it is. I think these things are designed so they have resolutions in "meters" or "tens of meters" which implies sub microsecond accuracy at worst. There's several kinds: The Oblique/QVI sounder - 100 watts into an omni(-ish) antenna - 2-20 MHz chirp at 100kHz/second, for 180 seconds total sweep. They do the chirp once every 12 minutes. Wide Sweep Backscatter Ionogram (WSBI) sounder 20 kW(!) into a 2 element log periodic curtain pointed in the general direction of an over the horizon radar. 5-28 MHz over 282 seconds, also at a 12 minute cadence. They have some of these in Vieques PR, New Kent VA, and Corpus Christi TX. I would imagine the Australians have some associated with JORN (their OTH radar network). There are plenty of other sounders around, too. There's a USRP implementation of a receiver for various sounders from Juha Vierinen http://www.radio-science.net/2019/04/oblique-ionograms-between-sodankyla-and .html _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.