MSK?

poltergeisty · Aug 1, 2016

I can't post this in the tavern where it would be more suited since the mod prevents me of doing so. So I have no choice as to post here as this would be the most suitable subforum.

I have a garage door alarm that sends a signal to the alarm in the house in the 400 MHz band. I used a SDR to grab the signal and ran the recorded audio in Skysweeper Pro. Upon trying to decode the signal using all the modes available, it looks like this might be MSK or MPSK. I don't know what it is for sure. MSK seems like it could be it since the Hex decode is straight forward compared to MPSK. Also, MSK would seem like a prudent choice for this application since it's not that pron to interference.

Here is the MSK decode:

Code:

ff a0 00 00 00 00 00 00 00 00 1b ff

Here is the MPSK decode:

Code:

82 88 6c 2c 04 36 06 02 1b 03 01 6d 81 9e 00 00    ..l,.6.....m....
08 00

Audio sample here: https://www.adrive.com/public/k2PDES/sample digital alarm.wav This was recorded in AM. FM did not sound right.

Does MPSK stand for Multiple Phase Shift Keying or Minimum Phase Shift Keying? I'm thinking Minimum Phase Shift Keying which makes me wonder what Multiple Phase Shift Keying is?

What applications use MSK anyway and is this signal MSK?

Thanks!

Note that if this is moved to the tavern I will not be able to respond

ka3jjz · Aug 1, 2016

Sorry, but this has nothing to do with HF (below 30 Mhz)....moved...Mike

DaveNF2G · Aug 1, 2016

I think you'll have to ask the manufacturer which definition they meant. MPSK has 3 "official" definitions, including Mary Phase Shift Keying (not mentioned above).

gewecke · Aug 1, 2016

poltergeisty said:
I can't post this in the tavern where it would be more suited since the mod prevents me of doing so. So I have no choice as to post here as this would be the most suitable subforum.

I have a garage door alarm that sends a signal to the alarm in the house in the 400 MHz band. I used a SDR to grab the signal and ran the recorded audio in Skysweeper Pro. Upon trying to decode the signal using all the modes available, it looks like this might be MSK or MPSK. I don't know what it is for sure. MSK seems like it could be it since the Hex decode is straight forward compared to MPSK. Also, MSK would seem like a prudent choice for this application since it's not that pron to interference.

Here is the MSK decode:

Code:

ff a0 00 00 00 00 00 00 00 00 1b ff

Here is the MPSK decode:

Code:

82 88 6c 2c 04 36 06 02 1b 03 01 6d 81 9e 00 00 ..l,.6.....m.... 08 00

Audio sample here: https://www.adrive.com/public/k2PDES/sample digital alarm.wav This was recorded in AM. FM did not sound right.

Does MPSK stand for Multiple Phase Shift Keying or Minimum Phase Shift Keying? I'm thinking Minimum Phase Shift Keying which makes me wonder what Multiple Phase Shift Keying is?

What applications use MSK anyway and is this signal MSK?

Thanks!

Note that if this is moved to the tavern I will not be able to respond

. MSK = Multi shift keying. MPSK = Multi phase shift keying would be correct. I know it used to be used with RTTY , maybe still is, but I never got involved with it. I think there might be autokeyers that can use those modes too, but a hard core CW operator would know for sure. 73, n9zas

jwt873 · Aug 1, 2016

I know D-Star uses GMSK which stands for Gaussian Minimum Shift Keying.. So it would seem that MSK would simply be Minimum Shift Keying.

Frequency Shift Keying (FSK) uses two frequencies.. A mark and a space. 'Multi' generally refers to the use of more than two frequencies (and not phases), and is referred to as MFSK (Multiple frequency shift keying).

slicerwizard · Aug 1, 2016

poltergeisty said:
This was recorded in AM. FM did not sound right.

So record/upload both AM and FM demodulated audio. Raw I/Q would be even better.

And what is the purpose of this? What do you actually want to do?

poltergeisty · Aug 5, 2016

Thanks for your responses. I was just curious to know what form of digital is being used by this garage door sensor alarm. I will see about recording different sound files in FM and Raw I/Q? I used HDSDR to record the audio. Not sure if I can grab raw I/Q.

Does anybody know where I can hear a sample of MSK? Apparently this would not be Multi, but maybe minimum shift keying. Sense it was stated above that Multi uses more than one frequency and that is not the case here. I can hear this digital code on one frequency in the 400 MHz band and only one frequency.

Just was curious as to what digital code they were using. If I could get an audio sample of MSK that may in fact help in determining whether this is indeed MSK. But I looked at that website that offers digital mode audio samples and could not find MSK.

jwt873 · Aug 5, 2016

Here's a sample of D-Star (which is GMSK). I'm not sure how much the Gaussian component changes the sound, but it should be fairly similar to plain MSK. http://www.w2sjw.com/sounds/D-STAR.mp3

poltergeisty · Aug 16, 2016

Sorry for the late reply. Been busy. Here is the raw captured file. I had AM mode on so not sure if that matters in a raw file or not. I just know you can barely here it in FM no matter what bandwidth I chose.

https://www.adrive.com/public/aNKpv3/AM.zip

MSK?

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