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Re: [Paparazzi-devel] Range testing for Xbee modems (2.4GHz)


From: Martin Mueller
Subject: Re: [Paparazzi-devel] Range testing for Xbee modems (2.4GHz)
Date: Mon, 23 Aug 2010 21:16:38 +0200
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.11) Gecko/20100713 Thunderbird/3.0.6

Hi Roman,

have not used the "Series 2" but could not find any hint that either of the XBee series would use frequency hopping, just spread spectrum. You can manually set the frequency with AT commands but it is not set to a non-occupied channel automatically or even changed in-flight.

Graupner wrote their own XBee firmware to have some simple frequency hopping before finally moving to the Weatronic system I think.

Martin

On 23.08.2010 21:03, Roman Krashanitsa wrote:
Hey Bao,
We did a pretty much same test about two years ago in the University of
Arizona, right in the middle of our campus. The ground station was
located on elevation about 10m from the ground (2nd floor of the student
union), and the othe modem was been slowly walked on a straight line
away from the ground station. We maintained a direct LOS all the time
and pretty much 100% of Freshnel zone due to elevation, at least up to
the point of signal loss. Again, some palm trees were around and of
course lots of wifi.
We had a video test, then data test, both on 2.4Ghz. The data test
showed lots of dropped packets starting at about 600m. Could not get
much longer than that. Video required amplifier and a filter - up to
about 1300m. As far as I remember, we used 3dbi patch antennas.
Hey Martin, long time no see! I think xbee also has something about
frequency hopping in its settings. We haven't used it, but I think it is
still there.
Sincerely,
Roman Krashanitsa

2010/8/22 Martin Mueller <address@hidden <mailto:address@hidden>>

    Hi Bao,

    the difference between XBee (at least XBee "Series 1") and a 2.4GHz
    RC is that some RC systems change its operating frequency if one is
    occupied or even jump with the frequency all the time whereas XBee
    stays at a fixed (user changeable) frequency. If that frequency is
    in use by Wifi, Bluetooth, analog video or even a microwave oven,
    the XBee will loose data or stop completely.

    The XBee range varies a lot with the noise level you have. It could
    be > 16km in a "calm" alpine scenario or just 100m in a noisy urban
    environment.

    Martin

    ----- original Nachricht --------

    Betreff: [Paparazzi-devel] Range testing for Xbee modems (2.4GHz)
    Gesendet: Mo, 23. Aug 2010
    Von: BX Guan

    Hey guys, this is a relatively simply question, but first a bit of
    background: My plane is controlled with a 2.4GHz system as well.
    Tried to do some simple range testing (as in, another group member
    walking around with it) yesterday on my uni ground so it is full of
    trees and probably lots wireless/bluetooth around as well. Now the
    question: of the several trials, my modems loses connection with
    each other at a very short range, somewhere within the range of
    ~100m to ~300m. I was testing the range of the RC system at the same
    time and it responds properly for about 1km, despite growing
    gradually slower and weaker towards the end. I was just wondering
    what exactly went wrong, as the modems themselves should have a
    range of at least the same if not more than the RC system. I had a
    9dB gain antenna plugged into my ground modem.  And if anyone's
    wondering, got the modems as part of the bundle from PPZUAV. Any
    feedback/ideas would be greatly appreciated. Thanks. Bao

    --- original Nachricht Ende ----

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