View Full Version here: : Radio Meteor Capture
30-10-2010, 11:56 AM
This is going to be confusing rambling to those of you who are competent radio operators. Although I did electrical engineering in collage some forty yeas ago all my working life I worked with DC power supplies, audio and security type electronics. So my knowledge of RF is very limited.
With the weather being awful for imagining astronomy and me being interested in meteors I have go few times on radio meteor capture. It seems that main application other people using is SpectrumLab. As I understand it they tune to some TV channel video carrier frequency some 500km distant. They use SSB function of their receiver to display carrier and sidebands. Passing meteors ionised trail reflect and shifts carrier frequency and it is displayed as line above or below the fundamental frequency. Others use SW radio frequencies more or less in same way.
Now Ė my problem is that I cannot for whatever reason to get spectrum display that clearly shows that meteor has passed between my location and RF signal origin.I had visually seen meteor but I can to recognise it on spectrum display. What would be best frequency to monitor from Sydney? I'm limited to SW or broadcast FM
Equipment Iím using- Tecsum PL600 receiver, headphone output fed to SoundBlaster line in input fed to (software) SDRRadio by Alberto I2PHD. The output of SDR is fed to on motherboard sound chip and displayed in SpectrumLab. Iím using home made folded dipole antenna made from 300ohm ribbon for FM and long wire antenna about 7m long 4m above ground sloping to 2m.
I would appreciate input from anyone who do radio meteor capture or Radio Amateurs operators.
I do realise that receiver Iím using is not very good but until I have $700 to spare for Icom or WinRadio it have to do.
05-11-2010, 08:40 PM
Weather is still awful so I persist with radio meteor capture. FM tuner is tuned to 91.5MHz Triple J Grafton and Tecsun to 9.150MHz USB.
In first image there is no activity.
In Second one there are some reflections on FM. It could be aircraft or meteor Ė but how do I know?
In third image Ė what in the heck is this?
Any comments and suggestions welcome.
05-11-2010, 09:48 PM
I too slowly learning more about Radio astronomy but in my situation I am a qualified Radio tech in industrial radio. I am not a HAM radio operator.
Radio Scatter is the best way to listen and from some site I have read the best freq to listen to scatter is 50 to 52 MHz on SSB or CW. This was a quick read.
The main reason is quiet zone, anything under 20MHz is subject to major atmospheric noises and other transmissions from HAM and commercial operators. Those frequescies are heavily subjected to solar noise. I used to work Northwest a lot in remote sites and we had special charts to determin SSB frequencies needed to use due to sunspot activity. Low MHz freqs are used for long distance as signal bounce off the atmosphere to obtain distance.
The only other way to listen to meteors is via Doppler shift which requires you to transmit a signal. I believe the US marine uses 40MHz although to do that in Australia could be frought with interference laws. You would need a licence and you may not be able to transmit on astronomical freqs.
I am doing some quiet studies on RA and hope to purchace a WinRadio setup as well.
I intend to purchace the high end version going right up to 3.5GHz
05-11-2010, 11:23 PM
Thanks for that Malcolm.
Have look on this site G7IZU Radio Reflection Detection Page
In Europe they are doing lot of radio meteor research by using TV video carrier frequencies, HF Sideband or Broadcast FM.
You can download Spectrum Lab to have go yourself on the meteor capture. It is freeware.
50MHz Ė yeah that would be nice but my two receivers canít tune to this frequency.
Iím looking on Alinco DJ-X11E as my main receiver. Coupled with SDR it may do the job. Best price here in Australia Ė Prestige communications $399. I know there are better options Ė but money is a big factor.
06-11-2010, 11:19 AM
I was a bit busy last night, but managed to get a glimpse of permanant radio transmission available to monitor meteors, in Europe and US there is a lot but Australia not a lot. The idea is to tune to the allocated frequencies and receive reflection. The reflection Doppler based on the transmitter location and distance can give more detail on the meteor.
The problem is whether you are in an area to receive proper reflections.
Interesting note when i was reading is that 50.?? MHz is the strongest ionisation but 144MHz is weaker but longer.
The receiver i am looking at will cost about $1500.00.
08-11-2010, 09:17 PM
Here is an interesting site:
http://home.mira.net/~reynella/skywatch/radio.htm (http://home.mira.net/%7Ereynella/skywatch/radio.htm) and he gives some good tips.
What he says is that you need "a halfway decent Yagi antenna" so your folded dipole antenna may not be the best for this sought of work as the gain will be too low.
IMHO before you try to record a meteor event see if you can detect it by listening to the event from the site quoted one should be able to hear an event. The question I pose (I do not know the answer) is where to point the directional antenna ?
If you can get hold of a VHF communications radio the SSB mode would be the mode to use as SSB only translates a portion of the RF spectrum to the audio range and this will show the characteristics of the event.
Good luck, this is really interesting stuff
Here is a design for a 5 element yagi antenna:
24-11-2010, 06:19 AM
Karls48, I hope you won't mind if a guy from the U.S. jumps in here.
I pulled up a list of FM broadcasters in the Sydney area, and the band looks pretty congested. I doubt that you'll have much luck with the FM band at your location. Here in Arizona, there are dozens of micro-power transmitters eating up the whole FM band.... a lot of them are tucked in valleys and I don't normally receive them, but I seem to get a lot of reflections off aircraft.
You might have better luck on SW. A few years ago I tried a program called R_Meteor, monitoring the government WWV transmitter (15 MHz) located about 1000 km away. I imagine you could use Spectrum Lab the same way. Using SSB mode, you should see the carrier continuously. Meteors will appear as "spots" roughly 10 Hz away from the carrier, they fade away within a minute or so. The 10-Hz Doppler separation from the carrier is caused by the ion trails being carried along by high-speed winds in the upper atmosphere.
You can also expect to see aircraft tracks - these typically last two or three minutes (or longer) and they typically cross right over the carrier.
Here's a shot from R_Meteor. The horizontal bright band is the carrier, and it is flanked by a couple of sidebands (possibly artifacts from my receiver). Time scale runs across the top.
At 1659 you can see a little blip near the carrier - this is a typical meteor reflection.
All the other junk appears to be aircraft.
24-11-2010, 10:47 AM
Nice image, We have fewer aircraft in Australia with the exception of Sydney and Melbourne but at least it would be great practice to seperate non meteors away.
We most probably don't have as many TV transmitter so our band is not that flooded. We may have quieter areas in the VHF Band. I think our ABC radio operate close to the best band to monitor reflections.
24-11-2010, 11:11 AM
Thanks, Malcolm. I'm not too familiar with Australia, but the population density maps suggest that the west coast might have fewer transmitters than the NSW area.
I also read that your television stations will transition to digital over the next couple of years. The U.S. went digital last year, and most stations which had been operating in the lower VHF channels opted for higher frequencies. Here in Arizona, that made it easy for me to monitor Mexican television transmitters (they're still analog) without any local interference.
Several amateur observers in Europe and North America are uploading radio meteor observations to www.rmob.org (http://www.rmob.org) - perhaps we'll get some data from Australia someday :)
24-11-2010, 01:17 PM
Hi Steve and welcome to IIS forum.
That is interesting image you posted. I gave up on monitoring FM stations (my old AKAI tunerís frequency was drifting badly anyhow) and got myself Alinco DJ-X11E. I know thatís not best choice but it was lowest priced wideband all mode receiver (scanner) I could find. Now I can monitor TV Video carrier on 64.260MHz from Coffs Harbour some 400km distant. With homemade folded dipole antenna pointing to zenith I get strong signal and hopefully avoid reflection from the aircraft Ė major flight path is about 15 km from my house and cuts right across the signal path.
On other channel Iím using Tecsun PL-600 portable radio tuning to Radio Australia on 31m band. I think that the transmitter is located around Townsville some 1500Km distant. It is only broadcaster on SW I can find here in Australia.
Your image is interesting because you can see Doppler shift of the reflections. All I can get so far is the carrier and sidebands getting brighter and on stronger reflections I can see the harmonics.
If anyone is interested in this have look at http://www.tvcomm.co.uk/radio/.
24-11-2010, 02:48 PM
Karl, for the past year I have been monitoring a Mexican TV carrier at 61.239 MHz USB, using an old Icom PCR-1000 (I imagine your Alinco would provide similar results). My Spectrum Lab plot looks similar to your carrier at 1130 Hz, and yes, quite different from the old R_Meteor plot.
Perhaps the difference between your SpecLab plot and my SpecLab plot might be due to the SpecLab settings.... brightness, contrast, FFT size, etc?
Since I started monitoring this Mex TV transmitter, probably around 1000 km distant, I haven't seen any aircraft trails.
25-11-2010, 08:05 PM
Here is the reflection on 31m band from army chopper flying around last night. TV carrier trace does not seem to be affected. It is difficult to interpret radio reflections plots and be 100% certain that the reflection belongs to meteor.
26-11-2010, 01:11 AM
Karl, if you want to see my SpecLab settings, I could post them here.
Something else that might be worth trying - if you download the Colorgramme software from the rmob website, you could use the "conditional actions" in SpecLab to detect "hits" and load the data into Colorgramme. Andy Smith has a good tutorial for programming "conditional actions" on his website http://www.tvcomm.co.uk/radio/how-to.html#Speclab
Or if you like, I could send you the "conditional actions" program I worked up (simpler than Andy's example). You would probably have to adjust some of the numbers for frequency, signal strength, etc.
Loading the data into Colorgramme would enable you to see daily and monthly summaries. Genuine meteor "hits" should be at a maximum around sunrise, and at a minimum around sunset. If a meteor shower occurs, that should show up on the monthly summary.
26-11-2010, 09:27 AM
Steve, I would appreciate if you send me your settings and conditional actions program. Please use Private Message.
I been using Mintron CCD camera for some years to automatically record meteors. But lately weather is so bad that I decided to supplement video observations with radio detections. Iím waiting for some strong and long meteor trail captured on video and compare it to radio echo.
27-11-2010, 04:49 PM
Thomas Ashcraft is doing similar work here in the U.S. - running an all-sky camera and monitoring RF meteor reflections -
27-11-2010, 08:42 PM
Steve, Iím chewing my way thru Spectrum Lab conditional programming so I got clue what Iím doing. So far - line 17 comes with division by zero error? Then I found out that Iím using different date format on my computer then what was default in Spectrum Lab. My Golly I wish that whole world use same units for everything. I donít care if it is meters, feets or lengths of string as long it is standardised. As far as aircraft reflections go Iím getting them on 31m with long wire antenna. The 64.260MHz carrier may not be affected because it is pointing at zenith. Iím going to make new antenna Ė the one Iím using was cut for 100MHz and uses 75 Ohm coax. Alinco antenna impedance is 50 Ohm. Although I do not think it will make much difference.
And again thank you very much Steve for your help to get my radio detection running.
28-11-2010, 05:30 AM
Karl, my pleasure - I hope it helps.
SpecLab is a powerful program, once you get a handle on it.
If you're seeing aircraft on 31m, I bet you're getting meteors too.... but they might be hard to see, there won't be much Doppler offset (maybe 5 Hz ?) at those lower frequencies.
Regarding the 50:75 impedance mismatch, I think that would cause about 5% power loss/reflection.... might be a big concern with a 10 kw transmitter, but I doubt that you'd even notice it for "receive only" applications.
28-11-2010, 02:28 PM
Well, here is first colorgramme of radio reflections meteors. Iím setting up old Compaq Deskpro EN computer as permanent capturing station. It is inconvenient to run it on my main computer. Now I have to wait for Monitor, keyboard and mouse switch to arrive in post. No more room in my shack Ė just as well the Deskpro is quite small. I will fit it in, somehow.
28-11-2010, 03:58 PM
02-12-2010, 01:40 PM
The Monitor switch has arrived and half a hour after I installed it Ė hard disk crashed on Meteor images machine. So Iím rebuilding it. I had bad year with @!#!! Computers Ė two hard drives and one power supply gone so far. Monitor switch is working OK. It is a good solution using one monitor, keyboard and mouse for two computers that spend most of time collecting data. It has been raining here for five days so if I can not capture images of meteors I can record radio reflections.
06-12-2010, 06:32 AM
In one of previous posts I said that Iím not getting any aircraft echoes from TV carrier. That was wrong, yesterday morning I had screen brightness control up and echoes from passing aircrafts were clearly visible.
Iím not registering that many meteors as I thought I would, but I think thatís due to using low gain antenna and pointing antenna at zenith. I think that only quite bright (overdense) meteors are captured. Anyhow, before it become permanently cloudy my video capture setup was not capturing that many meteors either. On some nights only four meteors per night. And thatís with 8mm lens that can see quite big chunk of sky and record meteors down to about 4 magnitude.
Now Iím trying to build some sort of BFO for Tecsun PL600 radio. Its FM coverage is 76-108MHz and there are few TV stations I could monitor in this frequency range. But build in BFO works only on SW band.
12-12-2010, 12:43 PM
Karl, it looks like you fixed the computer problem (?)
I'm just using a cheap commercial TV antenna, pointed toward the transmitter's azimuth, and elevated about 15 degrees above the horizon.
The Colorgramme plot in the preceding post seems to show a good diurnal trend. You could probably detect more meteors by adjusting the detection threshold in the "conditional actions" program.... as long as you continue to see a clear diurnal trend, I would say you are counting meteors.
Some of the guys on the rmob site have "hair triggers" on their systems. They routinely record a couple hundred meteors per hour. However, Chris Steyaert says that anomalous meteor streams become more obvious with lower hourly counts, so I tried to adjust my system's sensitivity to yield counts similar to Chris's.
15-12-2010, 01:19 AM
Yes the computers are fixed and working again. Computers are pain in the neck Ė if there is not problem with hardware then the software will play up. But what would we do without them. We had couple of clear nights so I spend some time outside with my telescope.
Geminid shower produced very few meteors so far, at least at my location. During two clear nights we had, my camera captured seven Geminid meteors, brightest Ė0.8 Mag. That count would hardly show up as meteor shower in Colorogram and it did not.
I consider this radio capture thing as an experiment and Iím not yet convinced that it is working correctly. So far Iím happy that I can see and recognise aircraft reflections and confirm it by looking on flight radar on the net. I also confirmed that the SpecLab is not counting those reflections as meteors. Next I need my camera to capture few Mag Ė2 or brighter meteors lasting couple seconds in right part of the sky. Then I can compare it with record of SpecLab capture and modify Conditional capture script if needed.
I think that the confidence in the data acquired would increase if one monitors two transmitters at different frequencies that are approximately in same line of sight. And count only reflections that occur at same time. Coffs Harbour and Townswille would do nicely.
I did build VFO and finished up with totally wrong frequency. Used wrong IF transformer did I. Anyhow it was interesting exercise. But I think that my electronic circuits building days are over. My hands shake and I can not see well. So I used old FM radio and coupled IF signal to the Tecsun. It did work Ė kind of. Frequency drifts and adjusting the signal level is difficult. Too high and Tecsunís noise blanketing circuit cuts in.
When the finances allows I will look for second-hand communications receiver.
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