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Re: [Paparazzi-devel] New Telemetry Hardware - Digi 9XTend

From: Chris
Subject: Re: [Paparazzi-devel] New Telemetry Hardware - Digi 9XTend
Date: Tue, 12 Nov 2013 00:08:23 +0200
User-agent: Mozilla/5.0 (X11; Linux i686; rv:24.0) Gecko/20100101 Thunderbird/24.0

I always use two 9Xtend OEM modems but the ground modem also has a usb to ttl serial (FTDI)
converter plus a 5v power supply (a normal BEC used for rc airplanes powered from 12v or a 2S lipo pack) capable of at least 1A.
The 9xtend modem needs 5v for the full rated power of 1w, if you only need 0.5W 3.3v will suffice.
Connect it to the Yappa as you would connect the Xbee modem but power it from a 5v power supply,
the Yappa's power 5v regulator should do just fine.
Since you use the transparent mode you only need to set up the baudrate correctly.
9xtend oem modems can only use 9600 or 115200 bps for over the air communication.
Set them using the digi setup program at 9600 bps over the air and 115200 over the cable (modem to autopilot or pc) and also i suggest to use the polling mode, set one as the master and the other as a slave by giving them different adresses (read the 9xtend oem manual and in particular the polling mode)
For the antennas use a minimum of 8db gain patch antenna for the ground station or even better a 12-14 db yagi which is much better.
Search for 900 MHZ GSM antennas and you will find plenty.
For the airborne use a dipole antenna or a ready made for 900 Mhz like this one (900 mhz wheel antenna):
Be carefull the wheel antenna has horizontal polarization which will give you the best range available
plus the lowest drag when correctly mounted on the airplane.
The ground station antenna can be setup with either polarization but the wheel antenna only works with horizontal polarization.
You can also buy your antennas from here, for the airborne antenna:
and for the ground station antenna:
I have used them and the small dipole antenna is a very good airborne antenna.
Finally buy some thin and long but shielded usb cable extension and use it for the 9xtend signals and power to the pc or to the autopilot, you will get much lower RFI with this kind of cable.
I hope i helped somewhat.

On 11/11/2013 11:27 PM, Jorge Pantoja wrote:
Dear all,
I am looking for a way to extend the communications range I currently have by getting the Digi 9XTend modems shown in the wiki. However, before getting them I would like to know some things:
2) I am using a YAPA2 autopilot board, how should I connect the 9XTend OEM modem to it? Can anyone help me describing a connections diagram?
3) How should I configure my airframe file to use the 9XTend modems? I am currently using Xbees and my configuration is the following:
<section name="MISC">
<define name="XBEE_INIT" value="&quot;ATPL2\rATRN5\rATTT80\r&quot;"/>
 <firmware name="fixedwing">
<subsystem name="telemetry" type="transparent">
<configure name="MODEM_BAUD" value="B57600"/> 
4) How can I achieve the range shown in the Paparazzi wiki (Up to 64km line-of-sight)? What combination of antennas should I use? I plan to use the 900 MHz band.
5) Is there any additional equipment you recommend me to purchase like antennas or cables to facilitate the integration process? or do you have any other suggestions? 
Best Regards,
Jorge Pantoja
Program Manager/Liaison
Phone: +593-989458127

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