Reading Wireless Air Transmitter using Arduino
- Thread starter Nickorossa
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OK, so I did a bit more research.
The Pelagic Systems used by a lot of different computers - FCC ID MH8A operates at 38kHz modulation not stated.
The latest Suunto 2014 - FCC ID RYP21162 operates at 123kHz with PSK modulation.
I did my tests with an older Suunto which I think dated around 2010.
The FCC website has lots a photos and test data to look at. There is one of the Suunto insides which shows a ferrite rod inductor so their transmitter must include an LC resonant circuit. However much too big to fit into the watch style computers for the receiver function.
21162 Diving tank pressure sensor with LF communication capability Teardown Internal Photos Suunto Oy (fccid.io)
Rgds Nick.
The Pelagic Systems used by a lot of different computers - FCC ID MH8A operates at 38kHz modulation not stated.
The latest Suunto 2014 - FCC ID RYP21162 operates at 123kHz with PSK modulation.
I did my tests with an older Suunto which I think dated around 2010.
The FCC website has lots a photos and test data to look at. There is one of the Suunto insides which shows a ferrite rod inductor so their transmitter must include an LC resonant circuit. However much too big to fit into the watch style computers for the receiver function.
21162 Diving tank pressure sensor with LF communication capability Teardown Internal Photos Suunto Oy (fccid.io)
Rgds Nick.
No luck getting anything from Scubapro or Ratio transmitters on my first try with the TinySA. It's my first spectrum analyzer, and I've got a lot to learn about it, so the problem is most likely chair to keyboard interface.
I may just resort to an antenna on my oscilloscope and run an FFT on the data. Should be able to get lower frequencies that way.
I may just resort to an antenna on my oscilloscope and run an FFT on the data. Should be able to get lower frequencies that way.
Make a simple Loop antenna that goes Around the AI units body, one turn of some semi rigid copper wire is enough. Attach the two ends of the loop to some cable with a connector that can plug into that SA. Bring the loop in slowly and watch that the signal is not overloading the front end. A single loop worked and could be rested around the AI.
You are not going to pick up anything using those straight wire antennas that come with the TinySA. That is the mistake I made! The signal has almost no E component it is almost completely M.
Did you ever figure out the type of modulation?
Yes it certainly seems to be FSK but after stacking some pics of the signal and looking at them vs PSI reading I am almost certain it is encoded. I kind of lost interest after that because I just don't have the time to figure out how it is encoded and worst yet I might find out it is encrypted as well. My Covid free time was up about a month ago so I had to start working again, that's why I am not here as much.
OTF
Coney Island Whitefish Biologist
Thanks for posting the info, will definitely be a good starting point for the next person to pick up the torch
I like this idea.
I was setting up my shop compressor when I remembered this thread, so I decided to hook up my transmitter and take a look at the output on my scope. I don't have a tank handy. I don't think it's FSK, PSK, or anything that sophisticated.
What I see looks exactly like CW modulation: a constant frequency carrier being switched on and off to create a burst, or train of pulses. The carrier is about 38kHz, the pulses are about 1ms long with a short gap in between, and some pulses are missing, which shows up as a much longer gap. Each burst is about 140ms long, and they're about 5 seconds apart.
Morse code also uses CW, but this is obviously not encoded like Morse. Morse uses long and short pulses, but here the pulses are all the same length with short or long gaps instead. I can't tell much more with my rickety old analog scope unless I figure out some way to capture the bursts for closer examination. Or borrow a storage scope.
Anyone with a storage scope interested in posting a few images of a complete burst or two?
I was setting up my shop compressor when I remembered this thread, so I decided to hook up my transmitter and take a look at the output on my scope. I don't have a tank handy. I don't think it's FSK, PSK, or anything that sophisticated.
What I see looks exactly like CW modulation: a constant frequency carrier being switched on and off to create a burst, or train of pulses. The carrier is about 38kHz, the pulses are about 1ms long with a short gap in between, and some pulses are missing, which shows up as a much longer gap. Each burst is about 140ms long, and they're about 5 seconds apart.
Morse code also uses CW, but this is obviously not encoded like Morse. Morse uses long and short pulses, but here the pulses are all the same length with short or long gaps instead. I can't tell much more with my rickety old analog scope unless I figure out some way to capture the bursts for closer examination. Or borrow a storage scope.
Anyone with a storage scope interested in posting a few images of a complete burst or two?
dm9876
Contributor
Cool to see progress, for digital modulation what you're describing is called OOK (on off keying) same as cw but obviously the code is not morse code but probably some Manchester encoded bit stream or something. I've been keen to do some reverse engineering on this too but don't even have a transmitter. Being 38khz signal, you can use a sound card if you have a good one. Sadly my laptops are only 48khz sample. Need one that does 96khz or 192khz, thats typically going to be a decent desktop pc or a external audio interface,
Dean
Dean
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