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Thread: Burst transmission

  1. #1

    Default Burst transmission

    Hi,

    I am considering the purchase of a 900x module with Chanalyzer Lab bundled.

    I need this for monitoring an 868 MHz network of wireless modules using a 'wireless MBUS' protocol (its a European standard).

    This protocol relies on short burst transmissions using specific channel allocations.

    What I need to know is can the Chanalyzer/900x handle short transmission bursts - of the order of a few milliseconds, and do anything sensible with them. I appear to be 'losing' packets and need to better understand why....

    Obviously I wouldn't expect it to sweep a range of channels with that resolution !!, just monitor a single 868 MHz channel and capture the transmission bursts as and when they occur ???.

    I have asked one of your UK dealers - but they cannot answer this yet....so I guess its a question for the designers ;-)).

    If it can handle this - I'll be ordering one today ;-)).

    Many Thanks

    Best Regards

    Graham

  2. Default

    Hi Graham,

    I really doubt the Wi-Spy will be able to capture the burst efficiently enough for your application. The way the Wi-Spy works is it takes very small steps across the band, and at each step it reports the amplitude for that frequency step.

    The 900x comes with Chanalyzer Lab which will allow you to adjust the number of steps taken across the frequency range (smaller steps = longer sweep). You can also adjust the frequency range down to 5 MHz. Theoretically you could choose a very small frequency range, with larger steps and a higher resolution bandwidth, and you might get the burst easier.

    How often does the burst occur? Do you need to capture all of them? Or would catching 1 every 4 or 5 be sufficient?

    -Trent

  3. #3

    Default

    Well it might work, hard to say.. Depends on how long the burst transmission lasts for. You definitely wouldn't see all of them, but might be able to capture it every couple.

    I've had it down to:
    Range=0.8 MHz
    Step Rate=23.434 kHz
    Res BW=53.571 kHz

    See image...
    Click image for larger version. 

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    I'm not positive what the sweep rate would be per-step in this case, but I can count 32 steps (at least) that the Wi-Spy 900x is getting which correlates to about 25 kHz per step, or the set rate of 23.434. One problem is that Chanalyzer Lab doesn't label the steps when you get down that small. It should read down to 0.1 MHz at least, but only shows it in 1.0 MHz increments (See picture). So while I would bet you could probably capture the data you are looking for, analyzing it is a little tricky.

    As a side not, you can try using the free chanalyzer v3.4 instead of lab to use with the 900x, but I think the 900x comes with Chanalyzer Lab anyways, but v3.4 will allow you to see down in -dBm further than Lab.

    Oxygen

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