Question! 72mhz or 2.4 for fpv?

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Question! 72mhz or 2.4 for fpv?

Postby lithoushine » Tue Dec 28, 2010 12:19 pm

I have been trying to get this setup working. 1500mw 900mhz system for my fpv camera and it works great but i'm using a Dx6i/ar6100e for my rc link and i keep losing signal. theres no glitching just a random lock out. it seems to happen when i'm about .25miles out. i tried to separate them but the most i could get was about a foot apart. i know that this powerful system is going to swamp my 2.4 stuff and i really dont know what to do? i was thinking about getting a AR6200 with the satellite receiver but i was also considering swapping over to 72mhz but i dont know enough to do anything yet. any ideas or information would be great .Thanks
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Re: Question! 72mhz or 2.4 for fpv?

Postby RCModelReviews » Tue Dec 28, 2010 7:14 pm

The Spektrum receivers are still based on a fairly old chipset (from Cypress) that was never designed to cope with very strong out-of-band signals (such as a 1.5Watt transmitter on 900MHz sitting just a few inches away) so it sounds as if your video transmitter is desensitizing the RC receiver.

Desensitizing is kind of like when someone (your RC transmitter) is whispering in your left ear while someone else (the video transmitter) is shouting in your right ear. Because your brain effectively "winds down the volume" to compensate for the shouting in one ear, you can't hear the whispering in the other.

I've noticed that the Spektrum receivers are quite sensitive to out-of-band signals (ie: signals not on 2.4GHz) -- to the extent that they'll sometimes even pick up ignition noise from gas engines -- something I've not observed on any other 2.4GHz systems.

Going 72MHz would likely improve the situation -- but make sure you use a PCM system so you still have failsafe in case you go out of range.

5.8GHz would be your best video option but you'll likely be limited to 200mW and so will need a hi-gain receiver antenna, possibly with tracking.

Alternatively, you could look at some other RC system.

As part of the FPV articles I'm writing, I'll be evaluating the ability of various brands to cope with strong in-band and out-of-band signals from video transmitters. Some definitely do better than others.
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Re: Question! 72mhz or 2.4 for fpv?

Postby lithoushine » Tue Dec 28, 2010 7:30 pm

thank you very much! this really helped!
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Re: Question! 72mhz or 2.4 for fpv?

Postby Asad » Thu Jan 06, 2011 12:19 pm

Bruce, any ETA for the articles regarding FPV?
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Re: Question! 72mhz or 2.4 for fpv?

Postby RCModelReviews » Sat Jan 08, 2011 6:54 pm

I'm writing as fast as I can :-)

I've done a video-review of the HK EPP FPV model on the RCModelReviews YouTube Channel and there's much more to come in video form with the web-articles close behind.
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Re: Question! 72mhz or 2.4 for fpv?

Postby Asad » Sun Jan 09, 2011 9:12 pm

Please do keep the website articles updated too! From just looking at your website, one would think that no updates were forthcoming.

I already watched the HK FPV vids and left comments within 6 hours of the second video being posted. :)
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Re: Question! 72mhz or 2.4 for fpv?

Postby lithoushine » Fri Jan 28, 2011 7:03 pm

hey Bruce, would futaba's fasst system work better? or what would be the #1radio setup i could use if i wanted to keep the same fpv setup or maybe an fpv system that would get really good range and work with 2.4? thanks
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Re: Question! 72mhz or 2.4 for fpv?

Postby RCModelReviews » Fri Jan 28, 2011 8:28 pm

Futaba's receiver design is somewhat more sophisticated and a lot more resilient than Spektrum so I would expect you to get much better results with it.

Right now I'm waiting on a 200mW 900MHz video system to do some direct side-by-side comparisons with the 5.8GHz system I'm presently using.

And yes Asad... lots of website articles here waiting for a bit of proofing and some editing.
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Re: Question! 72mhz or 2.4 for fpv?

Postby Buzzkill » Sun Jan 30, 2011 4:22 am

I'm relatively poor so I can't donate at the moment but, I can offer some help if needed/wanted. I have a tiny bit of experience with the sort of thing your doing and know how much work goes into it.
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