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 audiol problems I am just going to wrote this text version. It should suffice, but the video would have been useful to demonstrate the method I use, actually live, 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 the first address here, 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.
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 particular station, but I hoped that it might suddenly pop up via meteor scatter. Simple! In theory. But this gave me a minior 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 record the empty channel, together with the web stream, overnight.
Come the following morning, I would playe back my two recordings. I use WaveLab to do this. WaveLab has multi-channel playback via its "Montage" facility and can accommodate up to 256 channels, 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. So scanning through eight hours of recorded audio can often be done in a matter of minutes.
If I hear a burst, I quickly toggle to the web audio track 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 station heard via the recorded meteor burst. This is exactly the same thing many of us do when listening to tropo or E skip where we check the audio against that of the web stream.
StreamWriter. Multiple web stream recording!
The Software:
What if I could record more than web stream? Could I identify more than one station? Was there any software which would enable me to do this? I began to look into this and, to begin with, I looked at Virtual Audio Cable, but I had trouble configuring it to work with multiple instances of VLC Player. It would have been necessary to configure each VLC channel to play back different web streams. How could this be simplified? It didn't seem like an ideal solution. I began searching the internet for other software which might do the same thing, but more simply. Luckily, I found 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 that I tried. It seemed to do the job pretty well, so I stuck with it. I just need to make sure that all streams begin recording at the same time. StreamWriter is able to do this.
On to the next problem. StreamWriter renders the recorded audio to different formats. Some of these are not compatible with WaveLab. What to do now?
Any Audio Converter. Free audio conversion software
Any Audio Converter came to my rescue! All the formats which were incompatible with WaveLab could be converted to mp3. In fact, Any Audio Converter is able to process virtually any audio format intoany other audio format! I chose to convert all incompatible format to mp3, which was more than acceptable for this purpose. But then, some of the StreamWriter files had different bitrates and sample rates. No fear, Any Audio Converter can handle this too and in a single batch conversion!
The Playback:
Next, I load all the converted files, including the 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. These recored files can be 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 more useful, like mow the grass 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 unlimited Sky broadband package can handle this.
The Benefits and Pitfalls:
Once all the files are loaded into the montage, I simply play all the recordings simultaneously and toggle between each track. This helps me listen to each individual recorded stream. I can see if I have a match.
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 often be layed by more than one station on the frequency. The great things about meteor scatter is that you are sometimes able to hear the same station pop in and out several times in each recorded session, which adds weight to any logging claim.
- Beware of shared programming on overnight networks which can carry the same programming. Using Germany as an example, but you should be able to record ALL web streams from Germany in this example so you can be sure you have the identification correct.
- 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 all the above processes.
The Conclusion:
So, that's the theory. Now here's the practice. And this is where my poor quality video work comes in, but I think you'll see clearly enough what's happening in the following video.
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.
I hope this explanation is useful and may encourage other DXers to try their hand at meteor scatter DXing using multiple-channel stream recording.
Your comments and questions are welcome. I am happy to answer any questions.
Enjoy! This is John signing off.
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