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screenshot of the wave

signal more detail

I'm currently learning about signal modulation and fail to figure out the modulation of this signal - maybe someone can help me with it?

The software is GNURadio and the device capturing the signal is a bladeRF SDR. The device producing it is a remote control for home automation. A button was pressed to produce the signal. I'll try adding a new screenshot showing the signal in more detail. the documentation for GNURadio is here: gnuradio.org/docs

I would assume it's ASK, maybe with Manchester encoding. But what makes no sense to me are the long zeros with the small ones.

audacity screenshot

gnuradio graph for audacity screenshot

detail view of signal sample

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  • \$\begingroup\$ Thanks John - can I move it myself? I can't find an option. \$\endgroup\$
    – Omegavirus
    Jul 22, 2019 at 16:16
  • \$\begingroup\$ Click the flag link and choose the in need of moderator intervention option. Leave a message for the mods asking if they would migrate it for you. \$\endgroup\$ Jul 22, 2019 at 16:19
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    \$\begingroup\$ As an EE.SE regular, I'll say there's not enough information here to answer the question. What is producing the signal? What else do you know about it besides the presented chart? Can you make a plot zooming in on one of the signal bursts with enough detail to show the signal in detail? \$\endgroup\$
    – The Photon
    Jul 22, 2019 at 16:37
  • \$\begingroup\$ Also, what is the software being used to present the plot? Where can we find its documentation? \$\endgroup\$
    – The Photon
    Jul 22, 2019 at 16:39
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    \$\begingroup\$ I'm voting to close this question as off-topic because it has been abandoned by an asked who never provided the information needed to make it answerable \$\endgroup\$ Dec 25, 2019 at 13:33

1 Answer 1

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This looks like a kind of low duty cycle pulse width modulation.

A "short" burst of ~10 us indicates a 0, and a "long" burst of ~20 us represents a 1 (or possibly vice versa).

The long intervals between bursts, giving only ~5 bit per second overall data rate, serve to minimize the system power consumption.

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  • \$\begingroup\$ Having reversed a lot of OOK protocols, chances are it is not really a low data rate, but rather that we aren't seeing an accurate representation of the parts of the signal where the actual data is \$\endgroup\$ Jul 22, 2019 at 18:02
  • \$\begingroup\$ @ChrisStratton what would you need to determine the signal type in more detail? Would a wav or raw recording of the signal be of any help? \$\endgroup\$
    – Omegavirus
    Jul 22, 2019 at 18:22
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    \$\begingroup\$ Your problem may in essence be zooming in on the wrong parts. Try running a histogram of all of the "high" (signal present) durations and also all of the "low" ones. Typically you see preambles, data, and gaps between repetitions. \$\endgroup\$ Jul 22, 2019 at 18:37

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