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Old Feb 14, 2011, 01:01 PM
Just dog tired.
Wearyman's Avatar
USA, NY, Buffalo
Joined Dec 2010
459 Posts
I've been on the forums here for a while now, and need to ask what is probably a stupid question, but due to my own inexperience I just can't suss this one out myself. Hopefully IBCrazy will have mercy upon me and enlighten me with his technical wisdom.

There seems to be much discussion about RcTX and VTX and the proper way to balance these two. But with the advent of long-range multi-channel RX/TX systems (Such as Dragon Link and the like) Why are we not simply using a single RX/TX system and slicing out 2 or 3 channels to handle the video and audio downlink?

Perhaps I am missing something obvious, but if one has a 12 channel capable RX/TX system and is only using say, 8 channels, why not use the remaining 4 channels for your other onboard systems and save weight, battery, and complexity?

Has anyone ever tried this? Is it even POSSIBLE with a multichannel radio, or would you need to include some kind of chip-based compression/decompression system to get the video data stream down to a manageable size?

Thoughts? Suggestions? Rebukes for being ridiculous?
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Old Feb 14, 2011, 01:22 PM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
10,406 Posts
Lots of problems with this:

First, an RX does not transmit. You still need a transmitter on board the plane to communicate back to you.

Second, the bandwidth of a control system is a couple of kilohertz. The video feed is a couple of Megahertz. The video takes about 40X more bandwidth to transmit and recieve.

-Alex
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Old Feb 14, 2011, 01:39 PM
Just dog tired.
Wearyman's Avatar
USA, NY, Buffalo
Joined Dec 2010
459 Posts
Quote:
Originally Posted by IBCrazy View Post
Lots of problems with this:

First, an RX does not transmit. You still need a transmitter on board the plane to communicate back to you.

Second, the bandwidth of a control system is a couple of kilohertz. The video feed is a couple of Megahertz. The video takes about 40X more bandwidth to transmit and recieve.

-Alex

Now see, I SHOULD have known that first item. *forehead smack* Duh.

Of course, knowing the second items helps too. At least as far as the video is concerned, it's a bandwidth issue.

So really, what we need is a unified TX/RX - RX/TX unit that encapsulates both systems on both ends, along with a built-in video compression/decompression module that can handle both NTSC and PAL video streams from a variety of sources.

If only I had the technical knowhow...
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Old Feb 14, 2011, 03:50 PM
Never trust laughing dolphins
Joined Feb 2011
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Quote:
Originally Posted by kstmark View Post
horrible. I have 2 of them. I bought a much more better from www.securitycamera2000.com
I disagree. It's not bad for it's price and still cheaper than most random other cameras too, even if you decide to change the (often scratched) lens for a new one.

I'd say it's worth a try for sure, especially in the early times when crashes happen, but you should pay attention to resolutions too and not just the price these cheap cameras go for.

Obviously people shouldn't expect an excellent quality for those prices, but for an FPV beginner it's not smart to start out with a modded GoPro camera or the like for sure.

Just my 2cts.
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Old Feb 14, 2011, 09:49 PM
FPV nut
traderdmb's Avatar
Sorrento, FL
Joined Nov 2010
704 Posts
Thanks in advance to everyone for your help. I see that this is a very helpful forum. SO I guess Ill start with my FPV configuration. Here Goes:

Easy Star with stryker motor and ESC running with mostly 2100 3s lipos.
Spektrum DX6i tx with 6100 RX

FPV-

Readymade 480 camera
900mhz rx with 8dbi patch mounted on Tripod. frim readymade
900mhz tx 500 mw power mounted on wing about 6 inches off fuse. also readymade

Eagletree OSD expander with data logger and GPS

receiver (spektrum) mounted outside of fuse just below removable hatch.

My question is pretty simple. I just don't have the nerve to head outside of 1500 feet. I have actually lost radio contact a couple of times temporarily but recovered. I think this may have been due to the direction my spectrum antennae was pointed. How far are you guys able to fly with a setup like this? Is my video tx situated too close to my other stuff? How far apart do they need to be? I see all kind of setups with the tx right in front of the wing.1500 feet just doesnt seem very far to me and with the stryker motor on this thing I can cover 1500 feet FAST. It does have great vertical clime though.

Also, i am considering a draonlink or something similar. Any suggestions?


Again, thanks for looking and helping.
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Old Feb 14, 2011, 09:59 PM
FPV nut
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Sorrento, FL
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Old Feb 14, 2011, 10:32 PM
bucket of prop wash
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reddinng CA
Joined Nov 2007
942 Posts
you should put pictures up on RCG it makes it easier for RGC people to view them
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Old Feb 14, 2011, 10:44 PM
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Daemon's Avatar
Lakewood, Colorado
Joined Aug 2002
28,479 Posts
Spektrum AR6100 is a parkflyer receiver. It is not, I repeat *not* a full range receiver.
If you're going to stick with Spektrum (not the most proven 2.4Ghz system for FPV) at
least something decent on there like an AR7000. Going half assed with your RC control
gear will only result in a lost plane.

ian
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Old Feb 14, 2011, 10:47 PM
FPV nut
traderdmb's Avatar
Sorrento, FL
Joined Nov 2010
704 Posts
OK, I can do that. Like I said, Im a nuub. Thanks for the advice, I will pick one up tomorrow.

I certainly didn't skimp intentionally on the receiver. It's just that I have about 6 of them so I slapped it on there. I didn't know it was a short range deal. Thanks a lot for letting me know. I am just glad I didn't lose my plane. I came real close to messing it up pretty good.
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Old Feb 14, 2011, 10:48 PM
FPV nut
traderdmb's Avatar
Sorrento, FL
Joined Nov 2010
704 Posts
I will read up and see how to post pics on here. It asked for a link so I just threw them up how I knew too.
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Old Feb 15, 2011, 12:11 AM
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New Zealand
Joined Sep 2009
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Quote:
Originally Posted by traderdmb View Post
OK, I can do that. Like I said, Im a nuub. Thanks for the advice, I will pick one up tomorrow.

I certainly didn't skimp intentionally on the receiver. It's just that I have about 6 of them so I slapped it on there. I didn't know it was a short range deal. Thanks a lot for letting me know. I am just glad I didn't lose my plane. I came real close to messing it up pretty good.
The ar7000 is ok for up to 2 km flights if you are careful with the installation. Get an extension (600mm) for the satellite receiver and put it as far away from the receiver as you can, I used to put receiver at the front and satellite on the tail but it can go out on the wing too.
Range test without fpv gear powered up, then test with fpv gear on and make sure no or minimal reduction in range check, trust me it's worth spending time to get this right.

Mark
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Old Feb 15, 2011, 01:11 AM
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Joined Jan 2011
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what kind of camera is best for FPV ?
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Old Feb 15, 2011, 06:26 AM
Never trust laughing dolphins
Joined Feb 2011
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Quote:
Originally Posted by shinee View Post
what kind of camera is best for FPV ?
That's a tough question to answer and it somewhat depends on what you're looking for. Most cameras will have a decent resolution, sufficient color depth and light adaptation to be suited for FPV flying, but I'd say you should look into the 50$ range for the better FPV cameras without the risk of buying the overpriced 'crap' (not literally crap in the sense of quality, just not very cost effective for something that might break in a crash).

You might want to look at build quality or improve the durability yourself by making a custom camera casing. Well worth spending some time and effort for.
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Old Feb 15, 2011, 06:28 AM
Never trust laughing dolphins
Joined Feb 2011
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Quote:
Originally Posted by mark hitchman View Post
The ar7000 is ok for up to 2 km flights if you are careful with the installation. Get an extension (600mm) for the satellite receiver and put it as far away from the receiver as you can, I used to put receiver at the front and satellite on the tail but it can go out on the wing too.
Range test without fpv gear powered up, then test with fpv gear on and make sure no or minimal reduction in range check, trust me it's worth spending time to get this right.

Mark
For what it's worth, Spektrum receivers often can't handle a lot of potentially interfering radio noise from nearby video transmissions, so I'd generally not advice to use Spektrum. The range is not all that matters here, some transmitter systems simply work better in this 'radio shade' of a video transmitter than others.
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Old Feb 15, 2011, 06:47 AM
FPV nut
traderdmb's Avatar
Sorrento, FL
Joined Nov 2010
704 Posts
Quote:
Originally Posted by mark hitchman View Post
The ar7000 is ok for up to 2 km flights if you are careful with the installation. Get an extension (600mm) for the satellite receiver and put it as far away from the receiver as you can, I used to put receiver at the front and satellite on the tail but it can go out on the wing too.
Range test without fpv gear powered up, then test with fpv gear on and make sure no or minimal reduction in range check, trust me it's worth spending time to get this right.

Mark
Can you suggest a better rcvr compatible with the dx6i?
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