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How much interference is normal with FPV video?

Posted by Alex on June 3, 2012 at 11:34pm

Hi there,

Just recorded my first flight on a Quad with Camera + OSD on board. Seem to be getting a sh*t load of interference and trying to work out what I should expect before I start trying to improve it.

My gear is:

  • ImmersionRC 600mW 5.8Ghz TX
  • ImmersionRC 5.8Ghz UNO RX
  • standard out of box antenna
  • MiniOSD
  • APM2
  • EasyCapture USB dongle + Acer Aspire Netbook for video recording (Fatsharks are on backorder)

Have attached the following video. To me it seems to have a lot of interference... The RX was ~ 50m away on the dashboard of my car.

Thoughts? suggestions?

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Tags: interference, osd, video
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Replies

  • Eddie Furey August 6, 2012 at 5:20am

    As previously mentioned, make, or buy, a pair of circularly polarized antennas. They will reduce your multipathing down to almost nothing. Also get your receiver antenna up high, 1m high or more is ok, 2 is better.

    Have a quick read about the Fresnel zone. I'll attach a Freznel zone spreadsheet I made so you can quickly get an idea of it's size. make sure the zone is clear of objects, especially metal ones like your car. :)

    Freznel Zone Calculator.xlsx

  • Crasher June 7, 2012 at 3:21am

    I've had some pretty good (solid to about 3KM) results on 5.8Ghz, here's what I've found to work:

    1. Circularly polarised antennas. Forget all that sticky up stuff, you need something like these:

    http://www.firstpersonview.co.uk/antennas/5.8ghz

    You need them on the TX and RX side.

    2. Take your RX out of the Faraday cage which is your car. The roof will make a far better base, and you can run your wires through the sunroof if you want to.

    3. I've recently switched from BEVRC gear to ImmersionRC, and, although it shouldn't make any difference, I seem to be getting better results on my 200mw BEV gear than my 600Mw ImmersionRC gear. It's early days, and I know this shouldn't be the case so maybe it's just bad luck until now..

    4. Circularly Polrised patch antennas are also a good idea for anything long range, less likely with a copter, more for fixed wing. Once again, the patch needs to be CP too.

    Regardless of comments, you CAN get good results on 5.8Ghz. I have. Good luck

  • Alex June 7, 2012 at 3:11am

    Righto. Wasn't as much rain around... so got out again today and took the receiver with me this time.

    Seems much clearer until it gets about 50m or so up and then the interference starts again (at about 4.30 mins). Is it better to have the antenna facing downwards or sidewise for flying above?

    Probably should add that I'm in the middle of a city (Sydney)... so there is also likely a lot of other noise in the air also. Off to the country on the weekend, so looking forward to trying out the gear there.

  • Chris Huitema June 4, 2012 at 6:58pm

    Does it make any difference if the motors are running? could it be electrical noise from the esc's. try taking the camera and tx with a lipo for a walk down the street without the rest of the quad.

    maybe also try taking the reciever out of the car and into a clear area. cars normally have alot of metal to block the signal (mines mostly plastic so im fine!) 5.8ghz is really only good for line of sight even trees will effect the signal.

    I plan on doing a antenna tracker pan and tilt setup with a panel antenna, using the ardustaion. just waiting for my 5.8ghz panel to arrive. 900mhz panel for the xbee's is here and ready and the ardustaion is pretty much ready to go. just need to find a good way to actuate it all

  • Jake Stew June 4, 2012 at 8:35am

    Hard to be satisfied with that!  5G is prone to lots of problems though.  Like it was mentioned, 5G is pretty LOS and just about anything can cause problems.  Vehicles can also cause problems because of the big metal frame and electronics.  Standard antennas are pretty crappy.  I find it's really hard to get good antenna results with higher frequencies, even 2.4g, which you'd think would be totally nailed down by now.

    I'd try some various types of range testing to isolate the problem.  Be sure to let us know your results.

  • Kevin Vertucio June 4, 2012 at 5:19am

    Can you share some photos of your setup? Using the standard whip antennas with 5.8GHz is not going to give good results. 5.8GHz is very sensitive to obstructions and objects infracting on the fresnel zone. Any parts of your frame or lipo obstructing the antenna can cause this. Also any obstructions of the LOS path between the two antennas will cause problems. I would try making (or buying) some circularly polarized antenna ( cloverleaf/skew planar wheel ) to give you better results.

  • Chris Huitema June 4, 2012 at 12:34am

    I run a similar tx/rx to that one. and mines not that bad.

  • Alex June 3, 2012 at 11:35pm

    Mmm... youtube didn't seem to embed correctly... also... I think the 'ghosting' is from the cheapo USB recorder

    https://www.youtube.com/watch?v=ncACKNpp_Do

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