Meteor detecting

[Neil WyattModerator @neilwyatt]

Has anyone here tried using a software defined radio to detect meteors?

I've got a £16 module, made a yagi antenna and after much sweat and toil got them to work with HDSDR.

With much advice from the astronomy forum, I've managed to detect a few meteors. Now I have to battle with a program called 'Spectrum :Lab' to achieve automatic recording.

[Neil WyattModerator @neilwyatt]

[Rik ShawParticipant @rikshaw]

With that Sky dish pointing earthward you are unlikely to receive anything other than Mrs Dales Diary or Gardeners Question Time

Rik

[Neil WyattModerator @neilwyatt]

Posted by Rik Shaw on 17/06/2018 20:44:51:

With that Sky dish pointing earthward you are unlikely to receive anything other than Mrs Dales Diary or Gardeners Question Time

Rik

Sadly the Sky dish is accurately aligned…

[Jon LawesParticipant @jonlawes51698]

Interesting project, I like it!

A bit off topic but I spent a bit of time trying to detect numbers stations; I never did find any. I imagine it would be quite eerie hearing the lincolnshire poacher for yourself…

[SillyOldDufferModerator @sillyoldduffer]

Posted by Neil Wyatt on 17/06/2018 20:30:03:

Has anyone here tried using a software defined radio to detect meteors?

I've got a £16 module, …

…

No but then I'm the man who failed last week to detect loud 60kHz MSF time signals from Cumbria with a £200 SDR module!

[John OlsenParticipant @johnolsen79199]

Our technique for detecting meteors is to sit in the spa pool on a clear night and watch the sky. Works quite well, the wife and I each saw one each last night. Not the same one because if you happen to be watching a different piece of sky, it has gone before the other one calls out. We also see quite a lot of satellites at times.

John

[john carruthersParticipant @johncarruthers46255]

Have you tried it on Jupiter yet Neil? or the sun?

[Rik ShawParticipant @rikshaw]

Thirty something years ago we were camping on a site by Chesil beach. It was a clear but moonless night around two in the morn and black as your hat when I unzipped the tent flap to visit the site toilet. What I saw near took my breath away. I have never seen so many stars in the sky before or since. I saw two shooting stars before I had even reached the lav – an unforgettable memory! (the stars – not the lav)

Rik

[Joseph Noci 1Participant @josephnoci1]

Interesting Neil.

From the screen-shot it appears you are working around 143MHz. What signal reflection is there at that frequency and do you know its source?

I have played quite a bit with this in the Amateur 2meter band, and have had many beacon contacts with a friend in Johannesburg (around 1500kn away) and another in Cape Town (around1800km away). We each had a 20watt 144.6MHz beacon and enabled it according to a round-robin roster – each enabled period lasting 24hours, and while one beacon was on, the other two stations listened with a narrowband SSB receiver – the signal was then captured by a sound card and some home-brew PC software, and time, duration, etc logged. Our receivers are very sensitive and narrow band to make the best use of the only 20watts of TX power and available signal to noise ratio.

Singular events – A smallish meteor and its fragments would give a signal lasting anywhere from 1/2 to 1 second while a good meteor shower could result in signals lasting 5 or so seconds, sometimes even longer. Over 5 years we had over 230 detections lasting more than 4 seconds.

A particularly good period was during MAY 2014, when Earth passed through Comet 209P debris – you may have observed interesting 'shooting stars' then? Oft occurring signals lasting up to 7 seconds were detected.

It helps to know of a specific signal location and frequency – to know where to aim the antenna. Also, the 'better' frequency range for detection lies between 30MHz and 100MHz, making commercial FM stations a very good source of signal. I am not sure of the sensitivity and noise figure of the front end of those inexpensive SDR devices, but I imaging it is 'cheap', so signal to noise ratio will suffer greatly. It would help a lot if you could fit a narrow band filter and good RF preamplifier ( 10 to 15db gain, or so) with a low noise figure ( less than 0.8dB is easy to achieve in the commercial FM band), up at the antenna. The filter should be after the preamp, and should be designed for around 5MHz bandwidth, maybe a 8 to 10 pole filter..We used a large strip-line filter, 2MHz bandwidth, with a cutoff of -60dB at 1MHz away from the center frequency..

Also interesting is that during very bright moonlight, the signal to noise ratio worsened,so detections on bright-nights was poorer.

I don't do it any more, as plastic antenna do not work very well, and any metal antenna lasts as long as it takes to put it up here..My PVC coated copper wire HF antenna have to be replaced every other year – the copper simply corrodes up into the sheath and dissolves..

 

Have fun!

Joe

Edited By Joseph Noci 1 on 18/06/2018 08:06:51

[John HaineParticipant @johnhaine32865]

Sorry to be a pedant but the Sky dish is an Offset Cassegrain, and as Neil says is accurately aligned when the boom with the LNB is pointing earthwards.

[Neil WyattModerator @neilwyatt]

This setup uses the massive Graves radar in southern France at 143.050MHz. The antenna is to a design specifically for that band, slight different to a 2M band one.

It should pick up a lot including the moon. It won't pick up sources like the sun – you can do that with redundant satellite dishes and a tuning meter, but the resolution is only about 30 degrees!

I went to a talk which prompted this experiment and they showed some maps which suggest most detections are of meteors behind the transmitter over northern France and the low countries.

My signals are mostly weak although its easy to hear the dropping 'plop' in most cases, one very few minutes. I had one weak but long signal that lasted several seconds but the frequency range was broad but stable so probably not a meteor. The typical meteors I have are sort, slightly sloping lines showing a rapid deceleration and doppler shift.

A filter is recommended but advice is that a preamp isn't essential as the Graves signal is so strong. The first improvement I can make is using a proper connector for the coax instead of just poking it into a BNC socket and taping it up

Of course, the advantage over sitting by the pool at night, is that you can do it at any time of day. I will be out for the Perseids in August though, hopefully detecting with camera, eyes, radio and ears*

There are a few ISS passovers today in front of, above and behind Graves which will provide a good test.

Neil

*hearing meteors is an interesting subject of its own, the theory is they generate LF radio that makes nearby vegetation rustle. Last year I heard a long, loud 'fizz' at the same time as seeing a long-lasting and large meteor overhead.

Edited By Neil Wyatt on 18/06/2018 09:33:46

[Geoff TheasbyParticipant @geofftheasby]

You can detect the sun with more than just a satellite dish. I have done that, but I also did it on 145 MHz, see Practical Wireless, January 2018. I can e-mail the article if required. You only need a 2m aerial, I used an HB9CV, feeding a 2m receiver, with the audio taken to a smartphone running a data-logging 'app' like Soundmeter. Then play back the recording into your PC and print as normal. I recommend Amateur Radio Astronomy, by John Fielding, 2nd ed, RSGB. I also find that SDR# is good for use with dongles.

Geoff

[Martin WParticipant @martinw]

I think you'll find that the SKY dish in Neil's picture is mounted as per normal and that it looks to be pointing down is an optical illusion which is partially due the fact that one can see the LNB support through the perforations in the dish, again standard for dishes in order to reduce weight and wind resistance. I agree that it is an offset axis dish, in the vertical axis, which means that the dish itself can be mounted more or less vertically and not at some angle approaching 30 deg, a space saving arrangement that makes installation easier and more compact.

[Neil WyattModerator @neilwyatt]

Hi Geoff, I was wondering when you'd notice!

How will I notice the sun compared to ordinary background noise? Will it just be a peak in the fizz? Yes interested to see the article.

Neil

[Andrew TinsleyParticipant @andrewtinsley63637]

When I was a teenager, I built a VLF receiver, It peaked at about 20 kHz (sensitivity that is), But it had a very broad bandwidth. I was looking for whistler mode propagation and it worked well for that purpose. However it picked up things I was not expecting. I hooked it up to a super low speed tape recorder so that I could dispense with listening via headphones.

I picked up US and soviet rocket launches (the trail of ionized gas was a perfect VLF signal generator) Similarly I picked up a couple of Russian nuclear atmospheric tests, including the very big "Tsar" bomb. I also picked up the relatively local Rugby GBR signals, I think these morse signals were for nuclear powered submarine communication.

So what has this got to do with meteorite detection in the 100 mHz region? Well I strongly suspect that an ionized meteor trail would radiate in the VLF and would be quite a large if very short signal. No way could it be used directionally, but then you wouldn't have to build a Yagi and point it in the right direction. My non directional ariel was simply a very long piece of insulated wire wound on a very large wooden frame.

Andrew.

[Geoff TheasbyParticipant @geofftheasby]

Hi Neil,

Yes, "tune for maximum smoke"! I'll send you a copy after lunch. You can still buy back numbers!

Geoff

[John HaineParticipant @johnhaine32865]

Ages ago I remember there was an article in Radio Communications about reflections of 2m (I think) signals from aircraft over the channel from France. Do you see any signs of this Neil?

[MuzzerParticipant @muzzer]

Posted by Andrew Tinsley on 18/06/2018 11:51:06:

When I was a teenager, I built a VLF receiver, ….so what has this got to do with meteorite detection in the 100 mHz region?

Andrew.

Wow, 100 milliHerz would indeed be VVVVLF!!

[SillyOldDufferModerator @sillyoldduffer]

Neil's photo of a heavy yagi balanced on top of a tall, slim, cranked, unstayed aluminium pole reminds me of an important guideline in Amateur Radio. If you're not laying awake worried on mildly windy nights, your antenna isn't high enough!

Please don't spoil the illusion by explaining it's just the camera angle. I want to believe that thing's 60 feet up and Neil regularly shins up the pole to make adjustments.

[JonParticipant @jon]

Quite light that 3 ele beam but will move a bit on the thin poles interlocked together. Might go around 50mph at 32ft.

If able to get it aluminium scaffold pole takes and absorbs the sway, have had stuff up to 63ft up using those poles attached to it (38 ft) above it for several years and relatively high up.

Used to like making HF beams.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Jon on 18/06/2018 16:54:55:.

…

Used to like making HF beams.

Having a gigantic birdcage on your roof should be a status symbol. Ideally it should glow in the dark. My neighbours are so unimaginative. They even think owning a lathe is eccentric. Ho hum.

[Andrew TinsleyParticipant @andrewtinsley63637]

Hello Muzzer,

Point taken, I must be more careful about my prefixes!

Andrew.

[Neil WyattModerator @neilwyatt]

Hmm… that mast is only 4m high, not 32 feet. It's stood upright for about 15 years with a weather station on top with similar windage…

[Jon LawesParticipant @jonlawes51698]

Posted by SillyOldDuffer on 18/06/2018 17:31:13:

Posted by Jon on 18/06/2018 16:54:55:.

…

Used to like making HF beams.

Having a gigantic birdcage on your roof should be a status symbol. Ideally it should glow in the dark. My neighbours are so unimaginative. They even think owning a lathe is eccentric. Ho hum.

If your lathe is eccentric may I suggest balancing the chunk or wedging the baseplate?

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