GRAVES: Reflections out of the blue
A GRAVES reflection from a meteor trail, August 21st, 2017 at 10:51 UTC. Received with FDM-S2 from Elad, a discone antenna and software V3 from Simon Brown
Undoubtly, a Graves is a fine French wine from the Bordeaux region in western France. So it is so surprise that also GRAVES is an extraordinary Radar station. It was built to detect and follow satellites and their debris. They sequentially cover from 90° to 270° azimut in five big sectors A to D, and change from sector to sector each 19,2 seconds. Each of this sector is further divided into 6 segments of 7,5° width, covered for 3,2 seconds each.
They are transmitting on 143,050 MHz. If you are in Europe and tune into 143.049,0 kHz USB, you probably will hear/see some reflections of meteors, airplanes and even spacecraft. The distance between the transmitter and my location is about 630 km, and for their southly directed transmissions, there most of the time is no direct reception.
So, if you tune into 143.049,0 kHz, you will see just a blue spectrogram: noise. If you wait for a while, some signals will appear out of this blue; see screenshot on the top. With Simon Brown’s free software Version 3 you may also take a level diagram in smallest time steps of just 50 milliseconds:
A level diagram of the meteor trail reflection from the spectrogram at the top, visualized qith QtiPlot.
This level diagram shows the big advantage of SDRs, working on the signals on HF level, rather than of audio level as with legacy radios. The latter additionally introduce e.g. noise and phase errors. Of course, you may also listen to this signal:
From this audio, in turn, you may do an audio spectrogram, possibly revealing further details of e.g. of the trilling sound like that from a ricocheting bullet: The Searchers (the 1956’er Western film by John Ford, not the British boy group from 1960 …) on VHF.
Audio spectrogram of the sound, revealing “packets” of sound which result in the trilling audio. At start, these packet show a width of about 42 milliseconds to be reduced to 37 milliseconds.
P.S. If you want to donate: my favourite Graves is from Domaine de Chevalier, blanc …
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Excellent work. Now all you have to do is to use this for meteor scatter communications. 🙂
DE AB3A
… thanks, Jake! But transmit-wise, I am only interested in HF – DXCC Honor Roll in the 1990’s with P5 als the last nail for that, with 5 W QRP in RTTY … 73 Nils, DK8OK
https://drive.google.com/open?id=0B7dAkFDsf7RwYVZLVXpEOXBoZFE
… thanks, Gerard, for this video with some extraordinary strong & long refections! 73 Nils, DK8OK
What you see (vertical lines) are reflections on planes between the radar and the receiver. They are not meteors which appear as horizontal (short) lines. The doppler can help you : about 1kHz per km/s of relative speed of the object.
… for a more detailed explanation with some examples please see: http://www.rfcafe.com/references/electrical/doppler.htm 73 Nils, DK8OK
You can also get good results with rtl_power (the simple FFT logger in rts-sdr tools) to collect data and SDR-heatmap (Python script) to create a nice waterfall image.
With something like : “rtl_power -f 143049k:143051k:1 -g 20 -i 1s -w hamming -c 20% -e 10m grave.csv”
Then mapping and get something like this : https://www.noyf.biz/wp-content/uploads/2017/08/grave.png
… thanks, Denis, this is a nice hint. Hope to get some of Laokoon’s power to struggle with Python …: Nils, DK8OK
Hi, can you share python script for visualisation ?? tnx and 73 de OK1CDJ
Hi, Ondrej – thanks, and I did this manually as just with any other calculation. But to write some easy Python lines is a great idea if someone does this calculations more often. 73 Nils, DK8OK
FYI, the Graves radar is near Dijon and quite far from Bordeaux. Graves is an acronym.
This is a video where you can listen the reflexions of the radar on planes, on ISS and on meteors.
73’s de J-Luc F1JEK
… thanks, Jean-Luc. I have also some Dijon mustard here, but für drinking, I rather prefer Bordeaux … Yes, I know about the location, but the acronym GRAVES seemed to have been chosen with some taste …: 73 Nils, DK8OK
🙂 sure.
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