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Re: [Paparazzi-devel] Xbee 868 uplink

From: Rui Costa
Subject: Re: [Paparazzi-devel] Xbee 868 uplink
Date: Mon, 25 May 2009 10:16:11 +0000

I have the Aerocomm AC4868 and when I read your e-mails talking about  the duty cycle. I'm sad.
ETSI requirements as specified in the ETSI EN 300 220-1 define the requirements for the 868-870MHz bands. For a
conducted output of 180mW and radiated outputs up to 500mW, the maximum allowed duty cycle is <10%. This
duty cycle is measured as the amount of TX time on, monitored over one hour and relative to a one hour period. Thus
for the AC4868-250, the maximum “on” time in an hour cannot exceed six minutes."
There is any solution better out there. With this duty cicle my project will not work. I'm designing an UAV for civilian use. I need a data-link solution for Europe. Any ideia? Or I have to gave up of all?
Best regards
Rui Costa
On Sun, May 17, 2009 at 7:56 PM, <address@hidden> wrote:

did you test the Pro868 in the meantime?

I can confirm Jeremy´s results.


The bandwidth of a 868MHz modem is much smaller than the one of a 2.4GHz. If you use the same telemetry file, the result can be an overloading of the downlink that will prevent the uplink to work very well. Removing some of the messages or at least increasing their sending period could solve your problem. I should be able to test this new modem next week I hope.


Jeremy MICHEL a écrit :

I am trying to use the new Xbee pro 868 MHz.
Downlink works well however I couldn't get the Uplink working reliably.
Sometimes I succeed in live changing aircraft's settings by multiple fast double-clicks... Not user friendly...

Datalink is configured in transparent mode which worked well with Aerocomm modems.

The code I used in "my_airframe".xml in order to configure the datalink:
<section name="DATALINK" prefix="DATALINK_">
<define name="DEVICE_TYPE" value="PPRZ"/>
<define name="DEVICE_ADDRESS" value="...."/>
ap.srcs += downlink.c $(SRC_ARCH)/uart_hw.c datalink.c pprz_transport.c

Any help is welcome,


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