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

From: Chris Wozny
Subject: Re: [Paparazzi-devel] XBee 868 MHz Issues with Paparazzi
Date: Tue, 10 Apr 2012 12:43:39 -0700


After spending a bit of time on the phone with some technical sales
reps at Digi, I've gotten a few answers:

1.) The XBee 868LP utilizes the G4 band which has an unrestricted duty
cycle, but only allows for 5 mW transmission. This is what I'll be
2.) Digi has got some new technology out called LBT + AFA (Listen
Before Talk and Adaptive Frequency Agility) which avoids the duty
cycle restriction by hopping frequencies every so often to keep in
line with EU regulations. I'm not sure if the XBee PRO-868 supports
this, but the XBee 868LP does.

I believe that solution 2 would require using the XBee API, but would
allow the 868 MHz range to be used as nicely as 900 MHz in the US
which is awesome. Just wanted to share all of this info with everyone.


On Tue, Apr 10, 2012 at 10:07 AM, Chris Wozny <address@hidden> wrote:
> After digging some more I found the sub band you were talking about.
> It's the 869.7-870.0 MHz G4 band. The only thing that worries me is
> that it can only transmit at 5 mW.
> - Chris
> On Tue, Apr 10, 2012 at 9:30 AM, Chris Wozny <address@hidden> wrote:
>> Christophe,
>> Do you know which sub bands can transmit 100% of the time? We really only
>> need a couple kilometers which is probably an overestimate. Also, are
>> modules that work on this band drop in replacements? The XBee 868LP can
>> handle 865-870 MHz which makes me think it should be able to get on this
>> less restrictive band via configuring the device.
>> Best,
>> Chris
>> On Apr 10, 2012, at 4:53 AM, Christophe De Wagter <address@hidden>
>> wrote:
>> 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:
>>> All,
>>> 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
>>> _______________________________________________
>>> Paparazzi-devel mailing list
>>> address@hidden
>> --
>> -Christophe

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