Received 433MHz signal not as expected

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Joined: Sun Jan 19, 2020 8:09 pm

Received 433MHz signal not as expected

Post by bernt77 » Sun Jan 19, 2020 8:26 pm


two years ago I recorded (and decoded) the signal of a 433MHz light switch successfully:
Signal recorded more than two years ago
Signal_2017.png (120.12 KiB) Viewed 1912 times
However today I tried to decode another 433MHz device and the recorded signal looks so strange, so I decided to record again the signal from the device from 2 years ago as I still own this device.

Unfortunately I was also no longer able to record that signal in the same way as I did it 2 years ago:
Same signal recorded today
same_device_today.png (74.35 KiB) Viewed 1912 times
Same signal recorded today (wave (db) view
same_device_today_db.png (218.95 KiB) Viewed 1912 times
What might I do wrong to get so strange recordings without clear 'binary edges' in the signal?

Any help is much appreciated.

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Re: Received 433MHz signal not as expected

Post by rtlsdrblog » Tue Jan 21, 2020 6:03 am

Are you using the AM demodulator?

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Re: Received 433MHz signal not as expected

Post by snn47 » Wed Jan 22, 2020 1:13 am

Did you use the same hardware, softwareversion and settings to record the files?
Did you use a soundcard and windows? Selecting not the correct device maybe the reason for the second one, selecting microphone instead of line in an explanation for the clipping in the old one.

The old one is not offset and symetrical around 0 reaching ±1 most of the time. The recent one looks linear and unclipped like the one, but shows ±0 and and the center at -50 (what unit?) which also makes no sence to me. The resolution in time also looks different, unless you recorded a different telegramme where duration differed to old one.

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