Meteor Scatter DXing, using WaveLab's "Montage" window
The Foreword:
For the last five months I have been trying to put together a video to demonstrate the system I use for my band 2 meteor scatter DXing. After being attacked by various technical problems I am just going to do this text version. It should suffice anyway, but the video would have been useful to show the method I use in action.
The History:
I used to do well with meteor scatter when I lived in Nottinghamshire, but I have had a lot of problems with noise levels since moving to Skegness, more so at my previous address, so I wondered how I might have more success with meteor scatter in terms of identifying these fleetingly brief signals. It all came about by accident really.
The Idea:
At the end of last year, 2013, I had an idea. I recorded an empty frequency on the FM broadcast band while simultaneously recording the web stream of a station which used that frequency, via its internet web stream. I couldn't receive that station, but I would hope it might suddenly pop up via meteor scatter. Simple? In theory, but this ave me my first problem. I only had one audio channel available on the computer. This was stereo of course, so the audio from my XDR would be fed to one channel, let's say the left side of the stereo channel, while the web audio would come in on the right side. It's easy enough to split these via your sound card mixer control panel. I would leave these recording overnight.
Come the following morning, I would played back the two recordings. I use WaveLab to do this. WaveLab has multi-channel playback via its "Montage" files and up to 256 channels are available, not that I am ever likely to use that many. With the audio from my XDR on one montage channel, and the web audio on another, I can toggle between the two, or play them back simultaneously.
I can quickly locate each meteor burst by scanning along the visual waveform. This is useful as it means I don't need to play all eight hours of recorded audio to hear the meteor bursts. I can actually see them. Thus scanning through eight hours of recorded audio can often be done in a matter of minutes.
So I hear a burst and then toggle to the web audio to see if I hear the same audio, allowing for internet lag of course. If there is a match, then it *may* be safe to assume the identity of the recorded meteor burst. This is exactly the same thing many of us do when we want confirmation of a received tropo or E skip signal for instance, we simply check it against the web stream. I say *may* be possible". This depends on several things, which I'm sure speak for themselves and which I will cover later in more depth.
StreamWriter. Multiple web stream recording!
The Software:
What if I could record more than web stream? Was there any software which would enable me to do this? So I began to look into this and, in particular, at Virtual Audio Cable, but I had trouble configuring it to work with multiple instances of VLC Player. Then I would have needed to configure each VLC channel to play back individually. How would this all work? My brain cell struggles to get around this little piece of software at the best of times, so I began searching the internet for other software which might do the same thing, but more simply. I was pleased to find several programmes which did the job, but which one was best? Eventually I settled with StreamWriter. Let's say this was the least problematical of those I tried. It may not be the best solution but it seemed to do the job pretty well, so I stuck with it.
StreamWriter has the drawback of not being able to record asx files, despite supposedly being able to do this, so I can only record m3u files. Pay close attention from here because this is where it starts to get complicated.
Any Audio Converter. Free audio conversion software
StreamWriter converts m3u files which end up on my hard drive as MP3 or MP2 files. Firstly, mp2 files need converting to mp3. Some of the mp3 files end up with different bitrates and different sample rates. mp3 files need converting to a common format so they can all be loaded into WaveLab simultaneously. I use Free m4a To mp3 Converter for the conversion of the mp2 files. Then I use Any Audio Converter to modify each file so they end up with the same bitrates and sample rates. Without checking, I think you can do all the necessary conversions with Any Audio Converter, so the "Free m4a To mp3 Converter" might be surplus to requirements.
The Playback:
Next, load all the files, including your recorded off-air recording, into a WaveLab Montage. This is time-consuming to say the least. Since I typically record 20 to 30 web streams simultaneously, sometimes more, with each one being as much as nine or ten hours long, I end up with a lot of data which takes a lot of time to convert and import. Thankfully, you can let the computer get on with this itself while you can go and do something mroe useful, like mow the garden or paint the living room. Yes, it can take an hour or two to load in all the files.
The Bandwidth:
A problem for some will be the enormous amount of bandwidth used when recording all these files. Typically, I transfer 500GB of data. or more, each month, but my Sky broadband package is supposed to be genuinely 'unlimited' regarding bandwidth. I spoke to one of their operators about this and he confirmed that this wouldn't be a problem, but somehow, I suspect that were I to exceed this amount they would say something or slow down my connection speed. So far so good.
The Benefits and Pitfalls:
All you have to do is toggle between each recorded web stream to see if you have a match, but it is important to be aware of a few potential pitfalls when doing this. There are also a few benefits. I have listed some bullet points:
By using this method of meteor scatter recording, it ensures you can rule out sporadic E being responsible for your catches as you will be seeing and hearing the DX as it happens, so you'll know instantly if a station came in via Es or meteor scatter.
- Since Wavelab shows you a visual representation of the audio, you can zoom straight to the meteor bursts without needing to play through the whole duration of the recording, making the task of listening very quick and simple.
- Beware of popular songs, which can be played, by more than one station on the frequency, at the same time. The internet lag will usually sort that out for you, plus I find you tend to hear each station several times anyway, which confirms the station you have received is the correct one. It's about using common sense.
- Beware of shared programming on overnight networks which can carry the same music at the same time. Using Germany as an example, it is advisable to record ALL web streams on the frequency to be sure you don't identify the wrong stream. Also be aware that there are shared classical music programmes between different countries.
- Meteor scatter can bring in stations which are not typically received via any other propagation mode. Some FM DXers describe a 'gap' between the outer limits of tropospheric propagation and the shorter distances associated with E skip. From my location, just about all of those big transmitters in eastern parts of Germany have been received.
- I have discovered that it is also possible to regularly receive very low power transmissions via meteor scatter, in the order of less than 100 watts.
- You don't need an elaborate antenna for this. My three element beam just one metre above the ground, and even an old home-made FM loop, have provided very good reception of meteor scatter propagation, even to RDS levels.
- A small drawback is the learning curve: It seemed quite daunting at first, but I quickly developed a knack and a system which simplified the processes involved.
The Conclusion:
So, that's the theory. Now here's the practice. And this is where the poor quality video work comes in. I think you'll see clearly enough what's happening though.
I hope this explanation is useful and may encourage other DXers to try their hand at multiple-channel stream recording.
Finally, an update: I have been asked to upload the video I have been trying to produce to demonstrate this method and had hoped to use in this article. This is far from complete and only shows a couple of brief examples. The quality is shocking and blurry. Odd to say I did this all in HD. Something obviously went wrong. I hope it's of use however. Please write to me if there is anything else you need to know about this or if there is something which needs clarification.
These are short recorded samples of me using the various software to identify meteor scatter. Both examples used are brief, but the second example was used more to demonstrate a meteor burst which was probably too short to be of use. User discretion is advised.
Your comments and questions are welcome. I am happy to answer any questions.
Enjoy! This is John signing off.
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