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Re: [Paparazzi-devel] XBee 868 MHz Issues with Paparazzi

From: Christophe De Wagter
Subject: Re: [Paparazzi-devel] XBee 868 MHz Issues with Paparazzi
Date: Tue, 10 Apr 2012 13:53:15 +0200

The XBee 868 with their theoretical 40km range are not unusable. You just need to consider the consequences of it being really a long range modem. 

There are some options to use them:

1) legal option: do not sent too much data, so others within the 40km radius can also use the frequency.
    1a) transmit less than 0.4 seconds every 4 seconds. 
    1b) fly less than 6 minutes when sending 100% of time
    1c) in between: e.g. fly less than 12 minutes when sending 50% of the time.

2) illegal option: reset your modem every 5min with a xbee-reset module and you can send 9600 kilobits non-stop both ways. 

Note 1: when the modem in your airplane stops sending because it sent too much already, then it still works and can receive commands for instance. It will just wait until the hour passes until sending again as the duty cycle rule applies to full hours. 
Note 2: also consider you can pick up data from others from quite far away. So make sure you program your unique ID's and safety codes for instance.
Note 3: for shorter range there are also different sub-bands on 868 that can send 100% of time.

On Tuesday, April 10, 2012, Chris Wozny wrote:

Due to EU regulations, we must use either 433 MHz, 868 MHz, 2.4 GHz
for IMAV2012. I was wondering if there have been any developments with
the 868 MHz band issues with Paparazzi or if it's still fairly
unusable. Also, does anyone know of any 433 MHz transmitters tailored
for AUTO2 outdoor flight? I'm curious as to why XBee doesn't make any
433 MHz modems...

- Chris

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