Is there a simple script one could build on for analyzing.sah files?
Nope, no script for the analysis, what I do is completely manual, all visual. Open a file, tweak/fiddle with some controls, paste the data into the Average window which does the auto drift algorithm, then I stare it for a minute, make some measurements, and repeat. Baudline is just a visualization tool, my eyeballs and brain do all the analysis work. Here is the command line:
baudline -session seti@home work_unit.sah
The "seti@home" session just stores the option preferences and window layouts, nothing special about it.
By trough at 1.4 I assume you're talking about cellphones?
The 1.420000 GHz trough is an artifact of the seti@home collection (radio) and splitter equipment. They notch out a strong tone that is caused by their quadrature tuner so that the distributed client analysis software doesn't get upset. One in every 256 work units has this. It freaks some people out when they see it on the screensaver. It looks like a big dip.
My viewpoint of the seti@home project is that they are a great source of high quality Radio Telescope signals. I let their program do it's science and I get to keep the work units. Seems like a fair trade. So far I have archived 5762 work_unit.sah files (~1.5 GB). Why?
Because I am an amateur SETI enthusiast and I wasn't satisfied with just watching the screensaver. Gaussians, spikes, triplets, phooey! I wanted to do more. So I collect every work unit and I analyze them myself with the baudline signal analyzer. It can read the.sah data files and it has a cool auto Doppler drift algorithm, nice displays,...
Despite the common mixing trough at 1.4200 GHz, and the stationary harmonic bleed-in interference, I have found a lot of interesting things in the data. Every now and then I run into a weak signal with a non-terrestrial Doppler drift rate. Sometimes they wiggle or pulse. Is it ET? Probably not, but it is exciting and fun. I should make a webpage of pictures.
[Disclaimer: Yes, I am an author of baudline and this is a blatant product plug.]
Sound is a vibration of air. What I was refering to was a tactile vibration, a form of direct coupling, see tactile transducer. Basically Mr. Twain was standing on a vibrating platform.
You think this is funny. I've got your brown noise generator right here.
Seriously though, all of this infrasound and the brown note stuff is myth. No one has ever actually proven that there is a cause-and-effect relationship. The source of this story is something Mark Twain wrote about a visit he had to Nikola Tesla's lab, and it was vibration, not sound that was the source.
I forgot to mention this in the parent post but baudline can also be used to generate infrasound. It has a built in tone generator that is fairly flexible (pure sine waves, linear or exponential sweeps, brown noise, various modulations,...). One of my favorites is setting a low and hi frequency span in the deep bass range and then modulating a sine wave with the brownian motion function (drunkards walk), it is like a warble tone.
Generating infrasound at high dB levels is difficult and potentially dangerous to you and your equipment so be careful.
The first thing to do is to test if your audio card can actually output infrasound frequencies. Many sound cards (and subwoofers) have filters that remove inaudible bass. This is easy to test with baudline and a loopback cable. Simply plug the line-in to the line-out on your soundcard and then have baudline's tone generator output a 14 Hz sine wave and see what (if anything) is recorded on the input side.
The next and far more difficult problem is actually moving enough air to create infrasound of any significance. Remember that output ~= Vd * Xmax * frequency^2 where Vd is radiating surface area and Xmax is excursion. Most subwoofers have minimal output below 20 Hz and some even have rumble filters that electronically remove inaudible bass. So this might be more of a project for DIY speaker builders. Also using a subwoofer with a ported alignment is a recipe for destruction unless the port is tuned to (or below) the infrasound frequency of interest. In anycase it is easy to over power most any woofer and make them bottom out at infrasonic frequencies. So be cautious, start with low volume levels. A good general rule is if it sounds bad then it likely is bad and it is causing damage so stop immediately.
DISCLAIMER: I am not responsible for any damage those actually foolish enough to follow my advice inflict on themselves, other people, audio equipment, or physical structures.
I too am worried that explaining mysterious phenomena away as simply "infrasound" is going to be over used. You can't hear infrasound which makes it an easy answer that is difficult to dismiss. But that doesn't mean it is worthless. You need to get scientific about it. If you have a spooky house or an unexplained natural phenomena you need to bring in the infrasound detector and measure it. It isn't that hard or expensive.
I'm a bass fanatic and infrasound has sort of been a hobby of mine for the past several years. Detecting infrasound (frequencies less than 20 Hz) is easy if you have the right equipment and it can be very fascinating, educational, and fun.
Capturing and monitoring infrasound is easy with a PC, low end sound card, and a cheap microphone. The key is having a low enough sample rate and a spectrum analysis program that is designed for monitoring long term events. I am the author of a Linux signal analysis program called baudline. It has many features that make it ideal for infrasound monitoring. For those of you who are interested in this sort of thing I would recommend checking out the image entitled -session basso on the Screenshots page, also many of Mystery Signals contain some interesting bass phenomena.
For baudline infrasound monitoring, some good starting command line parameters would be:
This will capture about 5 hours of data at a 500 samples/second rate which is good for frequencies up to 250 Hz. Increasing the -memory buffers to 230 MB, the decimation ratio to 64, and the -overlap to 100% will have a Nyquist frequency of 62.5 Hz and capture almost a weeks worth of data!
Last week I said it here and I'll say it again. This is seti@home's plan for BOINC. Modules the that download automatically without user intervention. BOINC is bad. It is going to be a huge security hole.
I like the seti@home project and I hope BOINC never happens. It will sap the project of its spirit and it most likely will drive many volunteers away.
I am worried that the seti@home project has lost its focus and gone astray. Seti@home was a romantic notion that captured the hearts and minds^h^h^h^h^h of many of it's users. Mindshare YES, brain power NO.
I think seti@home should transform itself from being a passive project to being an active project. Utilizing the spare CPU cycles of a million idle computers is great but utilizing the millions of idle minds that stare at the screen-saver is revolutionary. Imagine the computing potential. It's incredible.
I know the Seti League's project Argus is a volunteer effort, but unfortunately most of us don't have the space, money, skill, or time required to build a seti microwave station in our own backyard.
My idea is to collect high quality microwave data from antennas such as Arecibo and Parkes and distribute that to users over the internet. Instead of (or in parallel to) a seti@program client, the user would use a signal analysis tool such as baudline to search for drifting signals. Search strategies would need to be conceived and programmed. A collaborative component would need to be built to allow IM like communication, second opinions, and instant peer review. It would be true distributed science that anyone with a creative mind and a computer could participate in.
Since baudline can read and decode the seti@home work_unit.sah files you can perform your own secondary analysis of the seti@home data. Baudline is free but it only runs on x86 linux so give it a try if you can. Most WU data files appear to be pure noise and are boring to look at but occasionally you get an interesting one. Auto-drift rulez.
The ukentucky link below a similar concept that is rough and needs more polish. The potential is there but the implementation is flawed. It also needs more volunteers.
WARNING: Upgrades that download automatically without any user intervention? Have they gone "BOINCers?" This is a very bad idea that will create an enormous security hole. My prediction is that most businesses that currently allow seti@home will ban the new BOINC system.
Do we really need another generic distributed computing platform like the failed or failing Popular Power, Process Tree, Entropia, Parabon, and Distributed Science?
participating in the university of Kentucky's volunteer SETI search project. Unlike the passive seti@home project, the ukentuckyasrgseti project requires an active participation.
Here is how the process works:
You download.wav files that were collected on the large dish at the university of Kentucky.
You analyze the data on your PC with the signal analysis program of your choice.
You choose your own search strategy limited only by your creativity, determination, and talent.
Any potential interesting hits are to be posted and discussed on the project website.
The project is very educational and I recommend it to anyone who has an interest beyond using a screen saver to search for SETI. Also for those considering building a SETI station in their own backyard, the knowledge learned working with the ukentucky project will be 100% transferable.
Hey, I don't like the VA Systems->Linux->Software scam.
They never were called "VA Systems."
I still have VA Research in my bookmarks. I get all nostalgic and weepy when I click on it. Oh how things have changed.
$500 is a great deal for a PS2 if ...
on
LinuxWorld Summary
·
· Score: 1
So... for $500 I can have something slower and suckier than a $500 PC. Why do I want to do this?
$500 is a great deal for a PS2 if you want to get a taste of, or try to break into the video game console market. Usually a game console development station is in the order of $10,000+ and they just don't sell those to anybody.
Just like the PS1 Yaroze was, this product is an enabling technology that is available to anybody. Truly cool if you ask me.
Also, a Linux based box that easily attaches to a TV and has 1394 built-in might just be a catalyst for some imaginative people to create the next new killer app. And it will run on Linux, not some other OS. This could be the force that brings the Linux Desktop into mass popularity.
You are confusing the window manager with X11
on
Xfree86 4.2.0 Out
·
· Score: 2, Informative
Everything from how the Windows decide where they want to be to really obnoxious icon placement just irks some people (myself and many people I know) about X11 and friends.
I agree that it is obnoxious when windows and icons are not placed where you want them.
But get your facts straight dude! It is the window managers fault and not X11's. The X server just does what it is told, layout policy is handled by the window manager just like the widget policy is a function of the toolkit (gtk, Qt, motif,...).
Linux doesn't have very good USB support at this time
This is just not true. I'm running a laptop with a 2.4.9 kernel and both the Telex-560 and Labtec Verse-704 USB microphones work great. They are much cleaner than the lousy ESS Maestro2 chip in my M300, and they are inexpensive! ($25 - $50)
support for Linux would make no sense to me if I was a developer - where's the real time recording software?
Excuse me. Check out a Linux program called baudline, it is a real-time recording and analysis program and it has no peer in either the MS or Mac world (or so I've been told).
Try the linux program called baudline, with a typical cheapo sound card, it's analog input to screen draw latency is less than 1/60 of a second. That is far from slow.
It is true, sound cards do have limitations when it comes to oscilloscope duty, but they are not as bad as many claim. I can't believe I'm defending the lowly sound card. It is time for some de-bunking. Let's go:
Almost all measurements with oscilloscopes cannot be performed with a sound card. However, if your application meets these...
Nothing you're interested in is outside the audio band (50Hz to 5kHz or so)
Low end sound cards with a 48000 sample rate are good from almost DC to 24kHz.
Up to a second delay for the screen update latency (depending on sound card) is ok
Check out a linux program called baudline, it's screen update latency is less than a 1/60 of a second. It's quickness will blow you away.
16 bit digitization (or worse) is enough
Huh? More bits is better. Since high-end digital scopes have 8 or 10 bit ADC's, the cheapo 16 bit PC sound card has far less quanization noise.
No hardware triggering (all done in software)
Why would you want hardware triggering? Deep buffers rule! In baudline you can scroll back to events that happened minutes or hours in the past (depending on RAM).
When dual channel, both have the same settings
What do you mean? Same sample rate? That isn't much of a limitation. Gain, zoom, offset,... can all be independently controlled via software.
Baudline is a real-time signal analysis tool and an offline time-frequency browser. It has a built in tone generation capability and it can play back audio files with a multitude of effects and filters. Designed for environmental analysis missions that range from modulation parameter measurements to searching for transient signals that go bump in the night, baudline combines fast digital signal processing, versatile high-speed displays, and continuous capture tools for hunting down and studying elusive signal characteristics.
Capture, analyze, measure, play.
Baudline isn't really an oscilloscope although it does have a waveform display. It is more of of an integrated spectral analysis laboratory with a built in function (tone) generator. Baudline currently only works with sound cards and is limited to a 192kHz sample rate.
Some folks have mentioned that computer sound cards are not really sensitive lab tools, this is true. But with a well grounded PC and a decent quality sound card like the $20 Sound Blaster PCI16 you can capture some good clean signal. For low bandwidth work the 16 bit ADC and DAC's in a PC sound card are actually far superior to the 8 or 10 bit ones that are found in todays digital scopes. So if you don't need MHz inputs, then check out baudline or the mirror, it is free, but it only runs on Linux..
Now this isn't as cool as hearing meteors unaided with my ears.
But while I was outside watching the Leonids here in Cupertino, I was also
watching and listening to
NASA's
Meteor-radar with a linux program called
baudline. There was a lot of activity
that night, about a hit a second. Unfortunately I can't correlate the radar
hits with the visuals since I live in California and the meteor radar is in
other states (NM TX and AL). Still it was cool.
Right now the meteor radar
is getting a hit about every 20 seconds. Sweet, I just saw a 70 second
streak with a doppler shift of about 183 Hz. That is screaming at about 17X
earth rotation! (If I wasn't so lazy I'd calculate that in MPH or m/s)
How did I do it? I just piped the real-time NASA stream into the standard
input (stdin) of baudline, then equalized it with about 10 seconds of
quietness, and then watched and listened away. I used this command line:
If the geocities site for baudline craps out, try again later, or try the
mirror site. The
downloaded md5sum for baudline_0.87_i686.tar.gz should be
72f949826ac81a461a8b4b5c5551f366
But there could be signals encoded in more efficient ways and thus look like noise. SETI@Home will never find them.
So true. The signal could come in some other form than the "spikes, gaussians, or triplets" that SET@home searchs for. That is why I save all of my work_unit.sah files and analyze them manually with www.baudline.com. (note: baudline only runs on x86 Linux)
In the 1000+ WU's I've collected and analyzed I have found many interesting signals that didn't match the S@H "spike, gaussian, triplet" profile. Some had the drift rate of a non-terrestrial origin but they didn't match Arecibo's beam width. Were they SETI? Probably not. But hey, it is a lot of fun to keep searching.
You can look for the presence of a carrier so weak that you can't detect the modulation, by averaging over many cycles. That's what SETI@Home actually does.
Baudline can also do this type of averaging with it's drift integrator tool. Coupled with baudline's color aperture window I've found that the human eye is very sensitive at finding signals in noise.
What would be really great is if the SETI@home project had a way for users to manually search for signals and send in feedback. Sigh, they probably would hate the flood of message they'd receive. Maybe I should start the SETI@home@baudline project?
Slashdot Mirror
Is there a simple script one could build on for analyzing .sah files?
Nope, no script for the analysis, what I do is completely manual, all visual. Open a file, tweak/fiddle with some controls, paste the data into the Average window which does the auto drift algorithm, then I stare it for a minute, make some measurements, and repeat. Baudline is just a visualization tool, my eyeballs and brain do all the analysis work. Here is the command line:
baudline -session seti@home work_unit.sah
The "seti@home" session just stores the option preferences and window layouts, nothing special about it.
By trough at 1.4 I assume you're talking about cellphones?
The 1.420000 GHz trough is an artifact of the seti@home collection (radio) and splitter equipment. They notch out a strong tone that is caused by their quadrature tuner so that the distributed client analysis software doesn't get upset. One in every 256 work units has this. It freaks some people out when they see it on the screensaver. It looks like a big dip.
"we ain't found shit!"
.sah data files and it has a cool auto Doppler drift algorithm, nice displays, ...
I like noise. In fact I am fascinated by it.
My viewpoint of the seti@home project is that they are a great source of high quality Radio Telescope signals. I let their program do it's science and I get to keep the work units. Seems like a fair trade. So far I have archived 5762 work_unit.sah files (~1.5 GB). Why?
Because I am an amateur SETI enthusiast and I wasn't satisfied with just watching the screensaver. Gaussians, spikes, triplets, phooey! I wanted to do more. So I collect every work unit and I analyze them myself with the baudline signal analyzer. It can read the
Despite the common mixing trough at 1.4200 GHz, and the stationary harmonic bleed-in interference, I have found a lot of interesting things in the data. Every now and then I run into a weak signal with a non-terrestrial Doppler drift rate. Sometimes they wiggle or pulse. Is it ET? Probably not, but it is exciting and fun. I should make a webpage of pictures.
[Disclaimer: Yes, I am an author of baudline and this is a blatant product plug.]
Uhh, isn't sound basically a vibration?
Sound is a vibration of air. What I was refering to was a tactile vibration, a form of direct coupling, see tactile transducer. Basically Mr. Twain was standing on a vibrating platform.
You think this is funny. I've got your brown noise generator right here.
Seriously though, all of this infrasound and the brown note stuff is myth. No one has ever actually proven that there is a cause-and-effect relationship. The source of this story is something Mark Twain wrote about a visit he had to Nikola Tesla's lab, and it was vibration, not sound that was the source.
I forgot to mention this in the parent post but baudline can also be used to generate infrasound. It has a built in tone generator that is fairly flexible (pure sine waves, linear or exponential sweeps, brown noise, various modulations, ...). One of my favorites is setting a low and hi frequency span in the deep bass range and then modulating a sine wave with the brownian motion function (drunkards walk), it is like a warble tone.
Generating infrasound at high dB levels is difficult and potentially dangerous to you and your equipment so be careful.
The first thing to do is to test if your audio card can actually output infrasound frequencies. Many sound cards (and subwoofers) have filters that remove inaudible bass. This is easy to test with baudline and a loopback cable. Simply plug the line-in to the line-out on your soundcard and then have baudline's tone generator output a 14 Hz sine wave and see what (if anything) is recorded on the input side.
The next and far more difficult problem is actually moving enough air to create infrasound of any significance. Remember that output ~= Vd * Xmax * frequency^2 where Vd is radiating surface area and Xmax is excursion. Most subwoofers have minimal output below 20 Hz and some even have rumble filters that electronically remove inaudible bass. So this might be more of a project for DIY speaker builders. Also using a subwoofer with a ported alignment is a recipe for destruction unless the port is tuned to (or below) the infrasound frequency of interest. In anycase it is easy to over power most any woofer and make them bottom out at infrasonic frequencies. So be cautious, start with low volume levels. A good general rule is if it sounds bad then it likely is bad and it is causing damage so stop immediately.
DISCLAIMER: I am not responsible for any damage those actually foolish enough to follow my advice inflict on themselves, other people, audio equipment, or physical structures.
I too am worried that explaining mysterious phenomena away as simply "infrasound" is going to be over used. You can't hear infrasound which makes it an easy answer that is difficult to dismiss. But that doesn't mean it is worthless. You need to get scientific about it. If you have a spooky house or an unexplained natural phenomena you need to bring in the infrasound detector and measure it. It isn't that hard or expensive.
I'm a bass fanatic and infrasound has sort of been a hobby of mine for the past several years. Detecting infrasound (frequencies less than 20 Hz) is easy if you have the right equipment and it can be very fascinating, educational, and fun.
Capturing and monitoring infrasound is easy with a PC, low end sound card, and a cheap microphone. The key is having a low enough sample rate and a spectrum analysis program that is designed for monitoring long term events. I am the author of a Linux signal analysis program called baudline. It has many features that make it ideal for infrasound monitoring. For those of you who are interested in this sort of thing I would recommend checking out the image entitled -session basso on the Screenshots page, also many of Mystery Signals contain some interesting bass phenomena.
For baudline infrasound monitoring, some good starting command line parameters would be:
baudline -memory 50 -samplerate 8000 -decimateby 16 -overlap 50
This will capture about 5 hours of data at a 500 samples/second rate which is good for frequencies up to 250 Hz. Increasing the -memory buffers to 230 MB, the decimation ratio to 64, and the -overlap to 100% will have a Nyquist frequency of 62.5 Hz and capture almost a weeks worth of data!
Last week I said it here and I'll say it again. This is seti@home's plan for BOINC. Modules the that download automatically without user intervention. BOINC is bad. It is going to be a huge security hole.
I like the seti@home project and I hope BOINC never happens. It will sap the project of its spirit and it most likely will drive many volunteers away.
I am worried that the seti@home project has lost its focus and gone astray. Seti@home was a romantic notion that captured the hearts and minds^h^h^h^h^h of many of it's users. Mindshare YES, brain power NO.
I think seti@home should transform itself from being a passive project to being an active project. Utilizing the spare CPU cycles of a million idle computers is great but utilizing the millions of idle minds that stare at the screen-saver is revolutionary. Imagine the computing potential. It's incredible.
I know the Seti League's project Argus is a volunteer effort, but unfortunately most of us don't have the space, money, skill, or time required to build a seti microwave station in our own backyard.
My idea is to collect high quality microwave data from antennas such as Arecibo and Parkes and distribute that to users over the internet. Instead of (or in parallel to) a seti@program client, the user would use a signal analysis tool such as baudline to search for drifting signals. Search strategies would need to be conceived and programmed. A collaborative component would need to be built to allow IM like communication, second opinions, and instant peer review. It would be true distributed science that anyone with a creative mind and a computer could participate in.
Since baudline can read and decode the seti@home work_unit.sah files you can perform your own secondary analysis of the seti@home data. Baudline is free but it only runs on x86 linux so give it a try if you can. Most WU data files appear to be pure noise and are boring to look at but occasionally you get an interesting one. Auto-drift rulez.
The ukentucky link below a similar concept that is rough and needs more polish. The potential is there but the implementation is flawed. It also needs more volunteers.
What are they thinking?
WARNING: Upgrades that download automatically without any user intervention? Have they gone "BOINCers?" This is a very bad idea that will create an enormous security hole. My prediction is that most businesses that currently allow seti@home will ban the new BOINC system.
Do we really need another generic distributed computing platform like the failed or failing Popular Power, Process Tree, Entropia, Parabon, and Distributed Science?
Here is how the process works:
- You download
.wav files that were collected on the large dish at the university of Kentucky. - You analyze the data on your PC with the signal analysis program of your choice.
- You choose your own search strategy limited only by your creativity, determination, and talent.
- Any potential interesting hits are to be posted and discussed on the project website.
The project is very educational and I recommend it to anyone who has an interest beyond using a screen saver to search for SETI. Also for those considering building a SETI station in their own backyard, the knowledge learned working with the ukentucky project will be 100% transferable.Hey, I don't like the VA Systems->Linux->Software scam.
They never were called "VA Systems."
I still have VA Research in my bookmarks. I get all nostalgic and weepy when I click on it. Oh how things have changed.
So... for $500 I can have something slower and suckier than a $500 PC. Why do I want to do this?
$500 is a great deal for a PS2 if you want to get a taste of, or try to break into the video game console market. Usually a game console development station is in the order of $10,000+ and they just don't sell those to anybody.
Just like the PS1 Yaroze was, this product is an enabling technology that is available to anybody. Truly cool if you ask me.
Also, a Linux based box that easily attaches to a TV and has 1394 built-in might just be a catalyst for some imaginative people to create the next new killer app. And it will run on Linux, not some other OS. This could be the force that brings the Linux Desktop into mass popularity.
Everything from how the Windows decide where they want to be to really obnoxious icon placement just irks some people (myself and many people I know) about X11 and friends.
...).
I agree that it is obnoxious when windows and icons are not placed where you want them.
But get your facts straight dude! It is the window managers fault and not X11's. The X server just does what it is told, layout policy is handled by the window manager just like the widget policy is a function of the toolkit (gtk, Qt, motif,
Linux doesn't have very good USB support at this time
This is just not true. I'm running a laptop with a 2.4.9 kernel and both the Telex-560 and Labtec Verse-704 USB microphones work great. They are much cleaner than the lousy ESS Maestro2 chip in my M300, and they are inexpensive! ($25 - $50)
support for Linux would make no sense to me if I was a developer - where's the real time recording software?
Excuse me. Check out a Linux program called baudline, it is a real-time recording and analysis program and it has no peer in either the MS or Mac world (or so I've been told).
Try the linux program called baudline, with a typical cheapo sound card, it's analog input to screen draw latency is less than 1/60 of a second. That is far from slow.
It is true, sound cards do have limitations when it comes to oscilloscope duty, but they are not as bad as many claim. I can't believe I'm defending the lowly sound card. It is time for some de-bunking. Let's go:
...
... can all be independently controlled via software.
Almost all measurements with oscilloscopes cannot be performed with a sound card. However, if your application meets these
Nothing you're interested in is outside the audio band (50Hz to 5kHz or so)
Low end sound cards with a 48000 sample rate are good from almost DC to 24kHz.
Up to a second delay for the screen update latency (depending on sound card) is ok
Check out a linux program called baudline, it's screen update latency is less than a 1/60 of a second. It's quickness will blow you away.
16 bit digitization (or worse) is enough
Huh? More bits is better. Since high-end digital scopes have 8 or 10 bit ADC's, the cheapo 16 bit PC sound card has far less quanization noise.
No hardware triggering (all done in software)
Why would you want hardware triggering? Deep buffers rule! In baudline you can scroll back to events that happened minutes or hours in the past (depending on RAM).
When dual channel, both have the same settings
What do you mean? Same sample rate? That isn't much of a limitation. Gain, zoom, offset,
From the the what is baudline? webpage:
Baudline is a real-time signal analysis tool and an offline time-frequency browser. It has a built in tone generation capability and it can play back audio files with a multitude of effects and filters. Designed for environmental analysis missions that range from modulation parameter measurements to searching for transient signals that go bump in the night, baudline combines fast digital signal processing, versatile high-speed displays, and continuous capture tools for hunting down and studying elusive signal characteristics.
Capture, analyze, measure, play.
Baudline isn't really an oscilloscope although it does have a waveform display. It is more of of an integrated spectral analysis laboratory with a built in function (tone) generator. Baudline currently only works with sound cards and is limited to a 192kHz sample rate.
Some folks have mentioned that computer sound cards are not really sensitive lab tools, this is true. But with a well grounded PC and a decent quality sound card like the $20 Sound Blaster PCI16 you can capture some good clean signal. For low bandwidth work the 16 bit ADC and DAC's in a PC sound card are actually far superior to the 8 or 10 bit ones that are found in todays digital scopes. So if you don't need MHz inputs, then check out baudline or the mirror, it is free, but it only runs on Linux..
Now this isn't as cool as hearing meteors unaided with my ears. But while I was outside watching the Leonids here in Cupertino, I was also watching and listening to NASA's Meteor-radar with a linux program called baudline. There was a lot of activity that night, about a hit a second. Unfortunately I can't correlate the radar hits with the visuals since I live in California and the meteor radar is in other states (NM TX and AL). Still it was cool.
Right now the meteor radar is getting a hit about every 20 seconds. Sweet, I just saw a 70 second streak with a doppler shift of about 183 Hz. That is screaming at about 17X earth rotation! (If I wasn't so lazy I'd calculate that in MPH or m/s)
How did I do it? I just piped the real-time NASA stream into the standard input (stdin) of baudline, then equalized it with about 10 seconds of quietness, and then watched and listened away. I used this command line:
mpg123 -s http://icecast.msfc.nasa.gov:8000/forward-scat | baudline -stdin -channels 1 -overlap 100 -fftsize 2048 -mem 9 -record -samplerate 22050 -session meteor_radar
If the geocities site for baudline craps out, try again later, or try the mirror site. The downloaded md5sum for baudline_0.87_i686.tar.gz should be 72f949826ac81a461a8b4b5c5551f366
But there could be signals encoded in more efficient ways and thus look like noise. SETI@Home will never find them.
So true. The signal could come in some other form than the "spikes, gaussians, or triplets" that SET@home searchs for. That is why I save all of my work_unit.sah files and analyze them manually with www.baudline.com. (note: baudline only runs on x86 Linux)
In the 1000+ WU's I've collected and analyzed I have found many interesting signals that didn't match the S@H "spike, gaussian, triplet" profile. Some had the drift rate of a non-terrestrial origin but they didn't match Arecibo's beam width. Were they SETI? Probably not. But hey, it is a lot of fun to keep searching.
You can look for the presence of a carrier so weak that you can't detect the modulation, by averaging over many cycles. That's what SETI@Home actually does.
Baudline can also do this type of averaging with it's drift integrator tool. Coupled with baudline's color aperture window I've found that the human eye is very sensitive at finding signals in noise. What would be really great is if the SETI@home project had a way for users to manually search for signals and send in feedback. Sigh, they probably would hate the flood of message they'd receive. Maybe I should start the SETI@home@baudline project?