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Corey

Is expensive equipment worth the money?

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After disappointing results using wireless equipment from several of the RC wireless websites I've been looking at getting some "higher end" equipment that is claimed to be of the quality required for military and law enforcement use. What I'm wondering is if anyone has gone this route and found that the relatively expensive equipment is really worth the money. Several of the companies I sent inquiries to have told me they have what I want and that those other companies I've bought from are using cheap Asian import stuff that isn't really what it's claimed to be, but I'm skeptical and somewhat new to this whole thing so any advice or experience of others is appreciated!

My inquiry to the various companies asked for an air to ground system that would result in noise and static free video for a distance of at least 1 mile, and not required to be LOS. The system I am most intrigued with is from dyplex.com and uses a 2W video tx on the 1800 mhz frequency with one of their standard receivers. The cost of the equipment with basic antennas and cables is about $7000 but they say it is worth the money and will do what I want it to do and more, most likely up to a distance of at least 3 miles.

Anyone know if this type of equipment is really that much better than other stuff you can find on the internet claiming to have the same specs at 1/10th the price? Maybe I'm just not using my antennas right on with all the stuff I've tried so far, which has already cost me several thousand dollars with no real success. I've got 900, 2.4, and 5.8 stuff up the ying yang with all sorts of fancy tripods, antennas, and diversity receivers and still every flight and/or video that I do has random static and drop outs from as little as 100 feet away...

Keep your responses simple because as I said, I'm still pretty new at this!

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My inquiry to the various companies asked for an air to ground system that would result in noise and static free video for a distance of at least 1 mile, and not required to be LOS.

Everyone's definition of "noise free" is different. So post a link to some of your typical flights so that we can see if your cheap Asian imports are working like they should.

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every flight and/or video that I do has random static and drop outs from as little as 100 feet away...

I don't think you'll find, even a system costing $7000 that will not have signal drop out under certain conditions, even the military suffers from drop outs, but if at 100', I would suspect antenna is not mounted correctly in the plane and is being shielded somehow.

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This video is typical of what I've experienced with most of my wireless exploits... This one uses a 500mw 900mhz tx with the stock whip antenna on the tx facing straight up from the EasyStar canopy. On the ground I am using an 8dBi HG908U-PRO Hyperlink fiberglass pole omni-directional antenna attached to a tripod stand that puts it about 12 feet off the ground. I don't think the aircraft is ever more than about 2000 feet from me in this video but it still has a lot of static and drop outs. Maybe I'm just expecting too much?

http://www.youtube.com/watch?v=Nv7jHHB7kxY

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On the ground I am using an 8dBi HG908U-PRO Hyperlink fiberglass pole omni-directional antenna attached to a tripod stand that puts it about 12 feet off the ground.

Most of your drops are caused by multipath interference from the signal being reflected off the buildings, your choice of rx aerial will invite this problem.

The only way to reduce this is to use an directional aerial such as a patch, this mean that you will have to point the patch at your plane or fly within its pick up area. You can improve thing further by using 2 or more patches with a diversity system, I use 4 to give me 360 deg coverage see here http://www.vimeo.com/1634177.

Try searching for Oracle, it will switch between 2 video feeds very fast to give a much better output. When used with simple whip aerials it will give far less drops and when used with patches will double your coverage, also can be used with a mix of both. You dont need to spend $7000 !

Terry

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As I can see both on that site, is the equipment they recommend you analog or digital? If it's analog I wouldn't expect much better results. The only parameters that would really affect performance are frequency stability of the TX and RX, and RX sensibility. Without figures for what they recommend you it's hard to judge, but the "cheap" gear we use usually isn't bad in this regard.

If it's digital then you start having error correction algorithms, the receivers can cope a lot better with issues like multipathing or even turn them into an advantage with diversity, and hide noise a lot more than analog. With analog you'd start having some static, then more and more as long as you go further - with digital you'd have a clean picture until a pretty distant point and then when it drops it does so very badly. That usually gives a better percieved quality, while not necessarily increasing range.

With regards to the setup in your video, firstly AFAIK the stock antenna of the 900MHz TX is known to be poor, there was a discussion about it on here lately. Do you have another one to try?

Secondly, a high gain omni on the RX side is usually a poor choice for 2 reasons: the first one is what Terry said - yes it will allow you to fly all around you, but that means it will also pick up multipathing and other interfecence coming from everywhere. The second one is that if you look at the diagram for that antenna, you'll see that its gain falls off at 10° from horizontal. That means the elevation of the plane above antenna level should not be more than this, or you could as well keep the stock $2 antenna and get the same results. But when flying, you're always above that. Now what links both issues - the antenna's highest gain is at 0° elevation (ground level) - exactly where all the interference sources (building walls, possibly other devices) are.

So what you do with that antenna is actually fly outside of its coverage, so attenuate what you actually want to receive, while amplifying all interference sources...

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Hi Corey - I feel your pain, especially as I have to FPV with a maximum power of 10mW here in the UK!

Just before you splash out $7K I'd strongly recommend you buy an Oracle diversity switcher, which you hook up to two receivers/aerials, and it will seamlessly flip between them, if one of them is briefly glitched by interference. Since multipath problems are very specific to aerial position, as long as the two aerials are spaced apart, it's highly unlikely that they'll both have multipath problems at the same time = clean video. I found this really improved things, although my video is still far from glitch-free thanks to Wifi etc.

Bear in mind too that the Oracle (google oracle diversity and you'll find several suppliers) is not only very cheap for what it does, but because it works downstream of the receivers, you can even try e.g. transmitting on two bands (e.g. 900 & 2.4).

You are flying surrounded by lots of houses (= wifi, other video senders, poorly-suppressed electric motors etc.); your example video looked pretty good to me for video from that sort of environment!

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Just a thought, if you require perfect video for making film or program then you could do what I do and record on board the plane and just use the live feed for aiming.

Terry

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I agree with the others. The big Omni on the Rx is wrong choice for your flying environment and the stock wire whip on the 900MHz TX is a low performer. I also heard (in a couple places) some repeating pop noises that are probably an RF source from the homes below.

Not all environments will give trouble-free results. The one you are flying in is packed with houses and other manmade structures. These cause multipathing. Plus there's humans in them that operate WiFi systems and other nasty RF-based things that cause grief. So, besides implementing the suggestions that have been offered, I'd add one more thing. Try changing flying locations.

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Man, you guys are smart! I've learned more on here in 24 hours than I did in 6 months of Google searches and shelling out cash to try what I mistakenly thought was going to fix the problem. I should split the $7K between you guys! I had no idea about the problems with the omni antenna but it certainly makes sense now that it's properly explained.

Terry, that video of yours is great! How do you set up 4 of the patch antennas to work like that? Are you using multiple diversity receivers in a sort of chain? Also what is the physical configuration of the antennas, and do you have them on the ground or up on a stand of some type? Is the 5.8 frequency part of the reason it looks so good or is it more in the antennas?

Lots of questions! Thanks everyone for the great ideas and information!

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Are you using multiple diversity receivers in a sort of chain? Also what is the physical configuration of the antennas, and do you have them on the ground or up on a stand of some type?

In effect I do use multiple diversity but it is of my own design but you could do it with off the shelf equipment. I mount them on on a tall tripod just over head hight.

Is the 5.8 frequency part of the reason it looks so good or is it more in the antennas?

Not sure if you mean the image quality or the lack of interference. I find 5.8Ghz a little sharper than 2.4Ghz but have never used 900Mhz. In fact that video was an early test and you can see the picture start to break up just before it switches to the next aerial, that problem is sorted now.

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post-16-1236801563_thumb.jpg

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In effect I do use multiple diversity but it is of my own design but you could do it with off the shelf equipment. I mount them on on a tall tripod just over head hight.

Those antennas are awesome! You should be selling them.

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