[time-nuts] another source of time...

[Lester Veenstra]

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
lester at 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-bounces at 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




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