|Subject:||Re: [Paparazzi-devel] New Telemetry Hardware - Digi 9XTend|
|Date:||Wed, 13 Nov 2013 10:22:36 +0200|
|User-agent:||Mozilla/5.0 (X11; Linux i686; rv:24.0) Gecko/20100101 Thunderbird/24.0|
I will try to be as specific as i can based on my experience.
If you go the analog way for video you could use this or something similar
http://www.readymaderc.com/store/index.php?main_page=product_info&cPath=11_30_38&products_id=919 and a nice 14-16 db yagi antenna but make sure you have a big aircraft due to rfi and video to modem-gps interference, If you have an aircraft with smaller than 1.7 - 2m wing span you can safely forget this option and stick with 2.4 ghz for video, 5.8 ghz is useless for over 20km.
The tx antenna must be located at the wing tip or right above or below the avionics, 0.5 to 1 wavelength higher or lower at least, for increased RFI protection.
if you get this from inside USA you will get the one channel version, you can find it on ebay also without restrictions, be carefull.
About long distance now.
It all depends on what you call long distance, if long <= 40km then use a 2.4 ghz @ 1W and a grid antenna but if long > 40km then you need to either use low frequency such is 1280 mhz with moderate power levels or an airborne tracking antenna at 2.4 ghz (have a look in the modules directory) sometimes in conjuction with increased rf power (normally i use 1W of rf power + 10dbd yagi).
The airborne tracking antenna + 2.4 ghz method is the best overall IMO as it has low RFI and low power requirements.
Other options are a high power (video tx +linear amplifier, have a look here: http://www.vfmstore.com/tr24.htm (i like the digital ofdm tx + a 2-5w bidirectional amplifier
from ebay) but this will significantly increase the overall weight of the aircraft due to increased power
It is "common" to see a 2.4 ghz 5w video tx on a 2m span+ aircraft which can have more than 70km of range.
I hope i made some sense.
On 11/13/2013 02:08 AM, GalapagosUAV wrote:
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