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Old Feb 14, 2007, 06:38 PM
Registered User
Massachusetts
Joined Jan 2006
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VideoLynx 434 Micro ATV Transmitter

Anyone have experience with this 2 meter video transmitter? A 35 cm dipole fits nicely vertically on the tail. I think I should get pretty good range on 100mW with just a folded dipole on my portable TV. (Although a helical antenna might give me much more range if I can find a volunteer to point it.)

I'm using a DX7 2.4GHz r/c transmitter and a bit concerned about also transmitting video at 2.4GHz. The issue is overloading the rc receivers' front end.

Also has anyone tried those video overlays for GPS and data that go between the camera and transmitter?
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Old Feb 14, 2007, 07:24 PM
rcrick
Prentiss, Ms.
Joined Dec 2000
216 Posts
INewton, There is more of a issue of overloading your RC receiver if you transmit video at 435MHZ. I have operated on this band both at 1 watt and 100mw. At the lower power it is manageable without much trouble, but at the higher power transmitters you will have to pace your RC receiver in a shielded box and build a low pass filter.

Good luck

Ricky
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Old Feb 14, 2007, 08:39 PM
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Elmhurst, NY (Queens in NYC)
Joined Apr 2004
7,030 Posts
Quote:
Originally Posted by INewton

[snip]

Also has anyone tried those video overlays for GPS and data that go between the camera and transmitter?
There is an interesting thread with guys programming their own On Screen Displays using an OSD chip, Basic Stamps and GPS's and whatever. If I don't see anything worth buying at the WRAM show I will probably heat up my soldering iron. I can do hardware but for some odd reason I really enjoy programming though I haven't done it for a few years.

http://www.rcgroups.com/forums/showthread.php?t=620418

This thread has gotten pretty long so rather than reading the whole thing, maybe you should scan for pictures and get an idea for what they are doing that way.

Pete
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Old Feb 14, 2007, 08:44 PM
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Renton WA
Joined Oct 2001
824 Posts
lots of early ATV was done with transmitters in the tv band. At that time, nothing was available in the 2.4ghz band. The results were pretty bad. esp with moving targets. As soon as 2.4ghz came allong, most everyone switched to that. Smaller antennas better range. If you do decide to try 435 mhz, you might look at some of the diversity antenna systems built for TV's in cars. They are much cheaper than 2.4ghz diversity systems. I have no idea if they really work, but if you do a search, I'm sure you will find them.

A number of people using spectrum radios at 2.4ghz have also gone to 900mhz video, which is another band that has been largely passed over.
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Old Feb 14, 2007, 09:03 PM
rcrick
Prentiss, Ms.
Joined Dec 2000
216 Posts
lupy, I have been using 900mhz for many years. I purchased my equipment from SuperCiircuits. I just recently purchased a used 1 watt 2.4 gig system hopeing to get better video. I was under the impression that at 2.4 gig there was more bandwith and therefore a sharper picture. I haven't tried it yet but I have been doing some reading over at the RC Cam site that this is not the case and that the range at 900mhz is actually just as good or better that 2.4 gig. Take a look at my videos over on you tube. Search for rcrick. I think the reason that 2.4 has caught on so well is that the antennas are smaller and some really like the 5 volt equipment.

Ricky
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Old Feb 14, 2007, 09:32 PM
JettPilot's Avatar
Miami
Joined Apr 2005
10,324 Posts
I Newton,

You are correct in worrying about 2.4 GhZ video transmitters interfering with your specktrum, there have been LOTS of problems with that, you will overload the front end, and also have issues at the ground station

The 2.4 GHZ video stuff is small, and works well. Why dont you just use 72 or 50 MHZ for your RC control system. It would be much easier and you would have no issues.

JettPilot
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Old Feb 14, 2007, 10:11 PM
rcrick
Prentiss, Ms.
Joined Dec 2000
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My Bad, I didn't catch the part where he is using 2.4 for his RC
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Old Feb 15, 2007, 08:05 AM
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Montreal,Canada
Joined Feb 2002
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When I began in FPV, effectively 2.4GHZ tx/rx was not available, and I was using 434Mhz, or should I say I tried to use it, but never succeed. I always get a lot of interference with my r/c receiver, all the servos was vibrating. You need good electronic skill to build bypass filter, I never succeed.
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Old Feb 15, 2007, 10:11 AM
Registered User
Massachusetts
Joined Jan 2006
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Here's a .5W setup, good for a mile or two. The 33cm band looks interesting since a 16.5cm vertical dipole can be put in the tail (get rid of the 'rubber duck').

The transmitter may have to go in a aluminum box and the spectrum antennas can be horizontal to minimize coupling.

Thanks for the input.
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Old Feb 15, 2007, 02:09 PM
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Montreal,Canada
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Quote:
Originally Posted by VRflyer
When I began in FPV, effectively 2.4GHZ tx/rx was not available, and I was using 434Mhz, or should I say I tried to use it, but never succeed. I always get a lot of interference with my r/c receiver, all the servos was vibrating. You need good electronic skill to build bypass filter, I never succeed.
I forget to say I was using 72Mhz receiver
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Old Feb 15, 2007, 05:18 PM
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Switzerland
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Quote:
Originally Posted by lupy
The results were pretty bad. esp with moving targets.
My first try was a 224MHz TV band 100mW TX. Never went up in the air as even on the ground it would already start dropping as soon as one end was moving indeed. TV tuners also often have pretty poor sensitivity, the range with the 100mW was ~200m...
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