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Using beeper tags with a SensorGnome

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    Yes, you can detect beeper tags with a SensorGnome.  You must still register the tags before deployment, but your pattern of pulses will be simpler than described on that page.  In general, you need to record your tag long enough for it to produce a sequence of at least 4 consecutive pulses.

    Beeper tags produce a sequence of pulses at a fixed frequency and regular interval.  One manufacturer produces tags which broadcast at 150.XYZ MHz, transmitting a pulse of fixed length at regular intervals (we're not sure to what extent these parameters can be specified when you order the tag).  The tags are distinguished by different values of XYZ, the kiloHertz portion of the frequency.

    For example, we have observed a tag with ID 337 which broadcasts at 150.337 MHz, emitting a 16 millisecond long pulse every 2.050 seconds.

    With the current software release, SensorGnomes can record pulses from these tags, including estimated transmitter frequency.  This is subject to some constraints:

    • by default, the SensorGnome listens to each funcubedongle radio receiver listens at a single ("central") frequency.
    • by changing the deployment file, the central frequency can be switched across an arbitrary set of values on an arbitrary periodic schedule, independently for each funcubedongle
    • in its default mode, a funcube operating at a fixed frequency can detect pulses from tags within approximately +/- 24 kHz of its central frequency.
      e.g. If listening at 150.300 MHz, pulses from tags broadcasting in the range 150.276 MHz to 150.324 MHz can be detected, and the offset frequency estimated to within a few tens of Hz.  A single SensorGnome can listen to up to 5 antennas simultaneously (one funcubedongle per antenna) in this mode.
    • by changing the mode in the deployment file, a funcube can be made to listen more broadly but with lower quality and using more processing power:
      • old funcubedongle Pro models can listen out to +/- 48 kHz.  One SensorGnome supports 2 funcubedongles in this mode.
      • new funcubedongle Pro Plus models can listen out to +/- 96 kHz.  One SensorGnome supports 1 funcubedongle in this mode.
    • depending on the tag's pulse shape, it is possible to pick up harmonic pulses from tags which are considerably lower in frequency than the funcubedongle is listening to, but with the current software, this is not reliable.

    How do I set up my SensorGnome to listen to my Beeper tags?

    1. Decide on what kind of monitoring you want.  Here are some examples:
      • single tag: use a deployment.txt file with a constant frequency, and use the web interface to change the listening frequency when desired
      • multiple tags within a 48 kHz total range (e.g. 150.050 to 150.098 MHz): set the constant listening frequency to the midpoint of the range (e.g. 150.074 MHz)
      • multiple tags spanning a large range (e.g. 150.0 to 151.0 MHz): set a periodic listening schedule, spending a fixed (or varying) amount of time at each of a number of frequencies chosen to cover the range of the tags.
    2. Change the deployment.txt file accordingly (see this page for details).
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