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XBee SX for ELEV-8 — Parallax Forums

XBee SX for ELEV-8

I recently completed a lengthy internship at Digi, and while there we completed the release of the XBee SX, which is basically a drop-in replacement for the XTend (and the 900HP in terms of specs). The regular model has similar range to the 900HP, but with much lower power ratings, and the Pro model is rated at 65 miles LOS. I plan on doing a ELEV-8 build soon. I know with FAA rules the 65 or even 9 mile range of either version is useless, so I'm thinking more along the lines of penetration. The Pro model can use up 900mw at full power. I know my around an XBee fairly well now, but I'm hoping to get the opinion of more experienced builders with drones, etc. Thanks!

1. Do you think the power (and money) of the Pro version is worth the extra punch?
2. Will the Pro at full power have noticeable hit to battery life?

Comments

  • xanaduxanadu Posts: 3,347
    edited 2016-11-08 01:20
    They didn't give you samples?

    65 miles LOS is with a high gain antennas which means it will be directional. Everything depends on the mission you want to fly.

    I've flow with 1 watt HD video transmitters using omni antennas. They use noticeable battery, but no where near what the four motors will use. It's a fraction of the flight time, for my setup it was around 2 minutes less than what my normal 400mw transmitter does.

    The inverse square law is a battery killer. 20mw with the right antennas will do the same 800mw with dipoles at the same range. The difference is 20mw uses less battery and your flight path becomes relative to the ground station antenna.

    900mhz is great for penetration, in the case of the Elev-8 the receiver would lose signal from the transmitter long before the standard version on the SX would lose signal with the other Xbee. Or it would go out of sight from you. Even if you were FPV I think it would be very hard to keep up with that signal.

    From what I can see the price difference is $65. Personally I'd go with the low power one if it will only be for the purpose of the quad. If you have other applications you might use it in, it's one hell of a radio in there...

  • They didn't give you samples?

    I didn't think about that until after posting, but yes, I can still buy any of their stuff at a significant discount. Since I already use 2.4 Spektrum radios, I'm only interested in the 900 MHz products, so figured the SX was the best choice since it's a more efficient 900hp.

    You make a good point with the control radio not being able to keep up with even the basic model. I'm still tempted to go with the pro since I get them for good price. Who knows, maybe I'll find something else to use them with as well.
  • Emiljt,
    Is there a lower power option through software? Being able to increase/decrease power on the fly might be useful.
    Jim
  • RS_Jim wrote: »
    Emiljt,
    Is there a lower power option through software? Being able to increase/decrease power on the fly might be useful.
    Jim

    +1

    I forgot all about that. That adds some flexibility to your setup.

  • These are the power levels for each (software collectible):

    Regular: 55 mA @ 13 dBm; 45 mA @ 10 dBm; 35 mA @ 0 dBm
    Pro: 900 mA @ 30 dBm; 640 mA @ 27 dBm; 330 mA @ 20 dBm

    If I did get the Pro, I would probably leave it in the lowest power level most of the time. Even at it's lowest though, the Pro still uses 6 times what the regular one does. But as @xanadu said earlier, that's not much when you're running four brushless motors the whole time. The Pro also has a lot of "growing room" for other projects (since I'm legally limited when it comes to UAVs) ;)
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