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Schottingham posted:Speaking of transmitters, does anyone know anything about this transmitter from hobbyking? Given the channels in the "tx spec" section, I'm worried some channels might be outside the 2.4G band, and I don't want any black trucks pulling up at my field... With 1000 mW (a whole freaking watt!) of radiated power from that puppy you probably need a license anyway. Unlicensed ISM band use is limited to 100 mW EIRP in most countries (but just 10 mW in the UK, for example). Check your country's regulations before operating such hardware.
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May 8, 2011 03:33
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Schottingham posted:1 watt is a lot of RF power? I'm in the US, and most of the information I can find about the 2.4 GHz band pertains to wireless networking (obviously). I came across these tables in a few different places, but I'm not sure I understand the difference between "point to multipoint" and "point to point". Either way, it looks like I'm okay up to 4 watts radiated isotropically; help me out if I'm misunderstanding that. Of course radio amateurs everywhere have totally different rules, so if I went ahead and got a ham licence, it would open up plenty of options. Schottingham posted:Also, is it really that as bad as I'm hearing to operate both your control and FPV systems in the same frequency band? It seems like as long as they're in different channels it should be fine--they work simultaneously for me at close range, but I guess I could see the out-of-channel noise being a problem if your control signal is already weak at some distance. Yeah, I've heard the same. I haven't tested it in practice, but if you could be absolutely sure your FPV Tx stays clear of the R/C channels it would work. In practice though, when you look at the the spectrum it isn't as clean as in theory, and even a little out-of-channel leakage from your video Tx system right next to the R/C Rx antenna would drown out your (relatively puny) signal from the R/C Tx in the distance. And especially if your FPV or R/C equipment, or both, do frequency hopping all over the 2.4 GHz band, it just might guarantee you get interference some of the time. I'm still going to go ahead and test if I could luck out and find some stuff that works together. For example I can try and set the 802.15.4 2.4GHz Zigbee radio for telemetry to use channels 15, 20, 25, and 26 that my RC perhaps isn't using. (Or at least try and not use the most crowded 802.11 channels, like 1, 6, and 11.) Helldesk fucked around with this message at 23:01 on May 9, 2011 |
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May 9, 2011 22:58
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Precise maneuvering requires precise positioning information and that isn't easy, or cheap. A dead reckoning inertial measurement unit is only simple in theory; in a real life flying platform there are all kinds of noise sources like vibrations that throw gyroscopes and accelerometers off over time. But, as processing power increases, the cost and size of electronics come down and become more and more affordable, you can cram all kinds of poo poo in an electronic brain. Even today hobbyists can easily field equipment that would shame a military piece of kit from the cold war. Still, all those precise maneuvers require either a good pilot or external sensors and processing in a lab. And lots and lots of retakes. But still, Skynet lurks: http://robots.net/article/3229.html
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Sep 11, 2011 04:17
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CrazyLittle posted:So here's a quadcopter I built, with an onboard camera. DT-750 motors and 1245 EPP props, right? How is your total weight? I have got 1045 props on mine and they work fine otherwise but they do not seem to produce enough lift to tax the DT-750 more than half their available power. I have been thinking about trying 1245's on mine but the cheapo ones perhaps cannot last being used so far outside their intended RPM or with the loads I would make them lift... and spontaneously snapping props on a quad are a Bad Thing.
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Oct 2, 2011 23:54
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Yeah, Dragon Link uses 435 MHz apparently, which is in the HAM range. ChainLink seems to say it's 431-435 MHz. OpenLRS seems to be 433 MHz. I wish there were more ISM bands with usable duty cycles and power allowed...
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Oct 14, 2011 16:46
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Oh sure, not hard especially if you have a hobby that deals with electronics. I was just lamenting that you probably can't use your HAM licence and thus the LRS radios for anything other than amateur, and thus hobby, purposes. Having a reliable (to a degree) radio control that isn't on 2.4 GHz would free that frequency for the video link. I'm going to go with the allowed 25 mW maximum on 5.8 GHz. I'm in Europe and I know that one guy on another forum went through a lengthy application process to have a permit to use 200 mW on 5.8 GHz for his video link - in a very specified area.  Looking at the frequency allocation tables, the lowest ISM band that might possibly be usable for anything is 869.650 - 869.700 MHz - if the duty cycle is < 10% and power is 25 mW maximum.
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Oct 14, 2011 21:18
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Vitamin J posted:There are 25mw 2.4ghz systems which you would have better luck with as long as there wasn't Wifi interference. 5.8ghz is awesome but you've gotta have at least 100mw. What I would like to find is an affordable low latency digital system that can use the maximum allowed 100 mW at 2.4 GHz. High-end professional stuff is out of the picture. A Raspberry Pi might be an interesting hacking platform... Meanwhile, I made these little friends to help with getting the most out of 25 mW:  Those are circularly polarized omnidirectional 5.8 GHz antennas that reject multipathing very well. I couldn't get the signal to degrade when testing indoors (very preliminary, just checking if the modules worked). A highly directive Rx antenna should also help, but there's no reason to get ahead of myself. These should be plenty to get usable video from within line of sight, which is all that is allowed anyway for RC vehicles. Even a kilometer should be doable with omni antennas, weather permitting - if I could just find equipment to tune them with for frequencies as high as these! As they are, they're probably ok enough to get started though. Helldesk fucked around with this message at 00:47 on Oct 15, 2011 |
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Oct 15, 2011 00:43
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Trabisnikof posted:Fair enough, only T-mobile uses 900mhz GSM in the US though. It's also a HAM frequency so get your licence (and, most importantly, the related know-how) in order before using it.
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Dec 15, 2011 20:30
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Trabisnikof posted:That's not true, 902-928Mhz is ISM and used unlicensed in a number of ways. You are right, I just checked and saw how it is on Region 2. Over here on this side of the pond the limitations are incredibly strict though; 863 - 870 MHz is one of our ISM bands but with 25 mW ERP and 0.1% duty cycle limits (yes, one promille), or a suitable protocol. Wherever you live, dig up your local regulations and familiarize yourself with them. Then you know not to trust people on the Internet. 
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Dec 15, 2011 21:05
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hayden. posted:I've been doing some research on the possibility of making a UAV-type RC plane I recommend checking out DIY Drones or at the very least their FAQ. I do wonder what the rules actually mean for free-flying gliders like paper planes though. Are you a terrorist if you throw one out the window of a skyscraper or on the tarmac at an airport? Paint an ad on it to make it commercial too.  FPV is a bit of a grey area. You can do it in a way where nobody has any room for complaints (line of sight, buddy box system with the "student" doing the video flying and the "teacher" at the ready to take over in case of technical trouble), or you can go all out and fly beyond visual range with no hope of recovery if the technology lets you down for just a moment - or anything in between. So far there have been no incidents that would have attracted regulatory attention to smack down on civilians, but with its growing popularity, who knows. Edit: A "model" airplane can go a long long way... Maynard L. Hill built one that crossed the Atlantic in 2003. http://news.bbc.co.uk/2/hi/europe/3145577.stm Helldesk fucked around with this message at 00:20 on Dec 22, 2011 |
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Dec 22, 2011 00:14
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