Re: [Paparazzi-devel] Long Range Flying Wing

[Stephen Dwyer]

Hey Eduardo,

This is very similar to what we used to experience before a correct
configuration. It occurred on the 9Xtends because the packets from the
ground collided with the packets from the air almost every time.
Incorrect delay, retry and other settings were not resolving these
collisions correctly. To determine exactly what happened, a logic
analyzer was a huge help, if you have access to one. For further
information, see:
http://lists.gnu.org/archive/html/paparazzi-devel/2012-05/msg00081.html

It definitely helps to carefully read through the manual and undertand
about each setting.

Hope that helps.

Thanks,
-Stephen Dwyer

On Fri, Jul 6, 2012 at 3:15 PM, Eduardo lavratti <address@hidden> wrote:
> Well, i am using xbee 900mhz and configured the ppz to work on 9600kbps.
> with this config i receive all telemetry data but is very dificult to send
> command to airplane.
> Some time i need to clic more than 10 time airplane accept the command.
>
> even change waypoint position is very difficult.
>
>
>> Date: Fri, 6 Jul 2012 20:09:52 +0300
>> From: address@hidden
>
>> To: address@hidden
>> Subject: Re: [Paparazzi-devel] Long Range Flying Wing
>>
>> Well i have flown to a point where the ground station with its 8db patch
>> could not receive well
>> the planes data but i was still able to give a command to the plane and
>> return it home which indicates
>> good airborne reception.
>> I use as stated the polling mode with no confirmation and retries are
>> set to 0.
>> I have set the addresses somewhere in the top range, FFF0-FFF1 i think
>> and changed the channel
>> to 9 (different hopping frequencies).
>> One day i had a problem communicating with the plane (the downlink was
>> fine)
>> and it proved to be the video tx.
>> Since then i have fitted filters to the video tx (high pass) and the
>> modem (low pass)
>> and all problems were solved.
>> The antenna and the modem have to be in a straight line otherwise SWR
>> will rise,
>> RF will flow through the wires all over the airplane causing havoc and
>> the antenna
>> radiation pattern will be greatly distorted.
>> The same goes for the video tx.
>> Chris
>>
>> Hi Stephen
>>
>> We configured our 9XTends according to your recommendation
>> (Acknowledged Polling Mode):
>>
>> http://paparazzi.enac.fr/wiki/Modems#Configuration
>>
>> As we are sending lots of telemetry and not using datalink joystick
>> control we chose the air module as the base. It gets pretty warm in
>> operation. In the workshop everything works fine.
>>
>> On the field we experience a very asymmetrical link: The telemetry
>> data from the aircraft gets well to the ground station, also at range.
>> But the commands from the ground station only get to the aircraft at
>> very close range. At range we don't get any commands from the ground
>> station to the aircraft anymore.
>>
>> Can you explain this behaviour? How do you achieve a symmetrical data
>> link?
>>
>> We still have a 90 degree bend between the modem body and the antenna
>> on the airplane. On the ground station we have them in a straight
>> line. Could this explain the asymmetrical link?
>>
>> Regards, Reto
>>
>> 2
>>
>>
>>
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