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Re: [Paparazzi-devel] 9Xtend and antenna options for 900mhz

From: address@hidden
Subject: Re: [Paparazzi-devel] 9Xtend and antenna options for 900mhz
Date: Thu, 6 Dec 2007 18:48:52 GMT

You make some really great motors Uttam!  You sent me some of your very first batch about 4 years ago and they were amazing!  Welcome to Paparazzi!  I'm sorry to hear about the gerber issue.  Over the years I have asked several people several times to post gerbers because I know how incredibly senseless and difficult it is to produce these from Eagle but so far no one has done so :(  Maybe you could post yours?  The wiki allows zip files to be uploaded.

The 9Xtend is sensitive to antenna quality and also the RFI issues are greatly dependent on the antenna quality.  A simple wire whip will not work at all (don't ask me how I know this) but you may be able to carefully design a proper dipole or such.  One solution is to take the black rubber whip antenna apart and solder the coax cable directly, but it's difficult to remove the RPSMA or MMCX connector from the modem.  If you attempt this, be careful removing the shielding as there are many 0402 passives inside that are very close to the shield.

The best solution I have found is to buy these PCB antennas with MMCX connectors and connect them directly to unmodified 9Xtend modules:

You should be able to get 3km range with the 9Xtend at 100mW power if you use a small patch antenna on the ground.  We have had success with the 9Xtend at 500mW power on a larger plane but the RFI issues are a great challenge at these high power levels.  Keep the antenna as far as possible from the sensors, servos, GPS, R/C, etc. and orient it so that it does not radiate toward any of these things.  Straight out the bottom or straight out the wing is best - do not put it on top where it will radiate onto the GPS.  You can use a higher power level on the ground (I use 500mW so that it can be powered by USB).


-- Uttam Chandrashekhar <address@hidden> wrote:

I seem to be full of questions! Sorry for that. Now that the GCS is setup and running, I have a query regarding the Radio modem. Our 4 layer PCB's are coming in tomorrow, so I hope to have the board ready, populated and ready to test by the weekend. We are using the 900mhz 9Xtend Maxstream modules, and the standard module comes with a massive dipole antenna. Since we require about 3kms range, can I replace this with just a whip antenna? (The radio modem at the RX will have the standard dipole antenna). If so, how do I go about adapting it to hook onto the Reverse SMA connector? The paparazzi site has some pictures of 900mhz antennas, but there's not much info there.


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