1KM Wireless Solution

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rafael_kl
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2012/02/27 07:36:48 (permalink)
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1KM Wireless Solution

Hi, I need to make a wireless communication between 2 PIC's, using USART preferably, with a range about 1KM (0,63 miles).

I've been searching some RF modules on ebay, but they're range are not enought, or the price is to high.

Could someone recommend me some way to make that communication? 

Thanks!!
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    WaltR
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    Re:1KM Wireless Solution 2012/02/27 10:15:41 (permalink)
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    Check the high power RF modules form Digi International.

    Is the 1 km distance "line of sight" or obstructed? This makes a big difference.
    #2
    DarioG
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    Re:1KM Wireless Solution 2012/02/28 03:47:18 (permalink)
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    Am I wrong, or the B or C versions of the MRF24J40 should do that?

    (I would like to try...)

    happy palestine!! :)

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    dlindbergh
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    Re:1KM Wireless Solution 2012/03/03 07:48:04 (permalink)
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    The MRF24J40MB gives me > 2000 meters of range; no problem at all.

    But it has to be line of sight (no obstructions).

    See here: http://nerdfever.com/?p=1457

    Here is a graph of LQI and RSSI against range (in feet) that I measured in practice:


    Both RSSI and LQI are scaled to the range (0...10000).  This is the very last graph from this blog post:  http://nerdfever.com/?p=1552 

    Note that the distance scale (the y-axis, in feet) is ONLY vertical; I was just measuring altitude, not distance.  The rocket (carrying the MRF24J40MB) landed ~ 1 km from the launch site (crashed, actually; see the post), so the actual distance is greater.  And there were no obstructions; just air.   Launch (T=0) was from a horizontal distance of about 30 meters.

    Also, note the two data dropouts around T=13 and T=25 seconds.  The range was pretty large then (over 2 km) and I did  not control the relative orientation of the antennas - one antenna was fixed (on the ground) the other was uncontrolled.  I think the gaps are when the antenna's radiation patterns were (by chance) in a particularly bad misalignment.  This shouldn't be a problem for you unless you can't control the antenna orientation.

    If you need more range between fixed points, you could also make a simple corner reflector to get a little more gain.

    Cheers,

    --Dave

    post edited by dlindbergh - 2012/03/03 08:04:21
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    DarioG
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    Re:1KM Wireless Solution 2012/03/04 08:10:14 (permalink)
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    Thank you Dave.

    happy palestine!! :)

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    WaltR
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    Re:1KM Wireless Solution 2012/03/04 12:36:10 (permalink)
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    Great real range data Dave.
    And the rocket stuff is really neat.
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