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Dropouts with 200mw 2.4Ghz...

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Old 02-28-2004, 11:33 AM
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stevennh
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Default Dropouts with 200mw 2.4Ghz...

I got the Aerobird up with my new bwav200 system. I am powering the tx with an s-bec and it seems to work very well with no noise from the speed controller (powered off flight battery). I am using a patch antenna (8dbi circular). I put the antenna (rx) at the edge of my field pointing towards the middle of the field at about a 45 deg angle (using a camera tripod). The quality is good, but I am still getting more drop-outs than I would expect with this setup. I have tried two channels and get the same results. The tx is mounted below my wing and the tx antenna is over the wing (straight up). Even while flying close in, I am getting drop outs. Any thoughs? I am going to try another flight with the standard whip and see what I get from that. I will post videos later today.

Setup: 200mw tx (2.4GHz, whip antenna), rx (8dbi circular patch), camera cx161 (330 lines), power from 8.4v flight battery with 5v switched mode converter (s-bec). Camera and tx are mounted below the wing on opposite sides to balance the plane.

Update: Here is a sample (please excuse the flying!)

[link=http://www.s93421871.onlinehome.us/dropouts.wmv]Dropouts[/link]

Steve
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Old 02-28-2004, 04:14 PM
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Default RE: Dropouts with 200mw 2.4Ghz...

Yeah, definitely getting more than you should. The dropouts are consistant with the plane's location I noticed as in you get them in the same places each time.
If you are putting trees and other objects between the plane and the antenna's line of sight that can cause it.
You might try a different location for the antenna. I stuck mine pretty much at the end of the field I fly at and only got a couple of dropouts when I was flying at altitude about where the X is:

ORIGINAL: stevennh

I got the Aerobird up with my new bwav200 system. I am powering the tx with an s-bec and it seems to work very well with no noise from the speed controller (powered off flight battery). I am using a patch antenna (8dbi circular). I put the antenna (rx) at the edge of my field pointing towards the middle of the field at about a 45 deg angle (using a camera tripod). The quality is good, but I am still getting more drop-outs than I would expect with this setup. I have tried two channels and get the same results. The tx is mounted below my wing and the tx antenna is over the wing (straight up). Even while flying close in, I am getting drop outs. Any thoughs? I am going to try another flight with the standard whip and see what I get from that. I will post videos later today.

Setup: 200mw tx (2.4GHz, whip antenna), rx (8dbi circular patch), camera cx161 (330 lines), power from 8.4v flight battery with 5v switched mode converter (s-bec). Camera and tx are mounted below the wing on opposite sides to balance the plane.

Update: Here is a sample (please excuse the flying!)

[link=http://www.s93421871.onlinehome.us/dropouts.wmv]Dropouts[/link]

Steve
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Old 02-28-2004, 05:05 PM
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Default RE: Dropouts with 200mw 2.4Ghz...

Here's what I would do for a test. The polarization of the patch and a whip are very different. This in itself is not good to have one type of antenna communicating with another type of antenna. Sure it works, but not perfectly. Without really knowing the radiation patterns... I would setup the patch and tilt it forward as if it was mounted on a wall at about 6' high. Then, lay the whip down on the wing. As long as you fly some distance from the RX antenna and stay "in front" or in the direction the patch is facing... I bet it will work fine. If you still get drop-outs... I would investigate your feedlines to both antennas. Any "small" problem will massively decrease the RF range. Have you tried a range test? This is another idea. Try carrying your plane a distance away and see where the actual limit is. Then have some one work with you and change the polarization of the whip and see which way works best. This will help determine what is the best orientation for both. Another issue could be RF interference. Normally, interference is racing horizontal lines, but sometimes it can simply destroy the picture for a moment or two.

Isn't wireless fun??? I make my living screwing around with wireless... when it works great whooooohoooo and when it don't... they call me-grin


Rob
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Old 02-28-2004, 06:44 PM
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stevennh
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Default RE: Dropouts with 200mw 2.4Ghz...

I did a range test before I flew. I did see drop-outs while carying the plane to about mid field. I figured this was due to being too low. I had another thought. There are at least two or three wireless networks in my neiborhood. I would not be surpized if they are getting in there when the signal gets weak. I should try a flight away from town and see what the results are. I will play some more with antenna position and polarity next time out.

Wouldn't laying the whip down create a null when heading towards the antenna (and flying away from it)? I realize that having the whip vertical will create a null when flying right over the rx antenna. I will let you know what I find out with more experiments.

Thanks for the hints guys.

Steve
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Old 02-28-2004, 07:15 PM
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Default RE: Dropouts with 200mw 2.4Ghz...

Hey Steve, not bad for a first video!

I finally shot some pictures of my T-hawk setup and posted a page:

http://www.yb2normal.com/thawkcam.html

At the bottom you'll see my reference to "challenging urban environments"... there is a lot more detail about it here:

http://www.blackwidowav.com/questionofthemoment.html

Another thing to keep in mind is that 2.4ghz is a pretty short wavelength, so very minor changes in tx and rx position can yield dramatically different results. That's why my mounting method of choice is duct-tape


Regards,
Bill
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Old 02-29-2004, 12:36 AM
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Default RE: Dropouts with 200mw 2.4Ghz...

Drop outs? I saw alittle RFI but you never really every lost video - which is what I call a "drop out". You could have easily flow this from a POV standpoint. Another thing you should consider is that 2.4 gig IS a consumer appliance frequency. Most phones and other wireless consumer appliances are on this freq. which could be causing you some interference. If you lived out in the country and your nearest neighbor was a mile away, then I'd say you have a beef. However, in what appears to be an urban environment, you seem to be getting a pretty solid video feed. Quallity looks good and the flying was great! You landed it didn't you

CTF
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Old 02-29-2004, 08:59 AM
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Default RE: Dropouts with 200mw 2.4Ghz...

Great tips Bill. I tried putting the antenna on the ground near where I was standing. This time I got nearly zero problems, very clean feed. As you and others stated, 2.4GHz is busy around here. Thanks again. Now for some altitude... In part of the video (if you look very close) you can see my flying buddy (I am not sure what kind of bird he is, but he likes the aerobird). If I am out in the AM, he keeps an eye on me.

[link=http://www.s93421871.onlinehome.us/groundantenna.wmv]Antenna On Ground[/link]

Update: Hey, what else is there to do on a Sunday morning. One more higher flight (more wind this time...)

[link=http://www.s93421871.onlinehome.us/highflight.wmv]Higher Flight[/link]

Steve
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Old 02-29-2004, 09:00 AM
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Default RE: Dropouts with 200mw 2.4Ghz...

Looks like I got drop-outs (multipath) and RFI mixed up. You are correct, it would seem that RFI was my problem.

Thanks...

Steve
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Old 02-29-2004, 06:48 PM
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Default RE: Dropouts with 200mw 2.4Ghz...

Excellent video Steve!

That "High Flight" vid is pretty clear and had relatively few "blips" from anything. That 200 mw system seems to do a yeomans job!

CTF
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Old 02-29-2004, 08:07 PM
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Default RE: Dropouts with 200mw 2.4Ghz...

After following Bill's advice on just laying the patch antenna on the ground, I got a bunch of very solid video today. I am very happy with the system.

Steve
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Old 03-06-2004, 10:31 PM
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Default RE: Dropouts with 200mw 2.4Ghz...

Sounds like you're the guy to get me started! I just bought the "spycam", tiny, color camera with 9volt lead ($89.00). Cam and tx, built together. I tried it today and got lots of fuzz (drop outs?) It was clear for maybe 5 seconds at a time and then fuzz for 5 and repeat. About 30 minutes of video over several flights yielded many great 5 second bits but none longer. Any advice to a beginner wireless aerial video guy? Antenna changes? Tx. 6" whip, Rx. 6" stubby (coiled?) Thanks for any advice.
Lou
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Old 03-06-2004, 11:07 PM
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Default RE: Dropouts with 200mw 2.4Ghz...

Can you help me get started? I bought a cheap @89.00 "spycam" video cam described in Quantum Hobbies as a good lightweight aerial cam (Perhaps cheap is my problem?). I got lots of dropouts with a few 5 second clear signals that made me itching to try harder. Can you suggest antenna or camera systems that work well? I have ZTV ELECTRONS Cam/TX, 50mw (cam and TX. in same little square about 1 inch on a side. (Tiny for cam and TX.) TX. has a 9volt pigtail. antenna is a 6" whip (thin wire) exiting the same 1" square. Pointing straight up. RX. is a 12volt, with a 6" "coiled whip? (thick) Pointing straight up. RX. has a fine tuning knob. System is 1.2 GHZ. Any advice would be greatly appreciated. Thanks.

Lou
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Old 03-06-2004, 11:39 PM
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Default RE: Dropouts with 200mw 2.4Ghz...

Lou,

Unfortunately the best advice *I* can give is "show me your credit card number"

Seriously, my experience in wireless video is limited to the hacked xcam system which I cut my teeth on, and the stuff I now sell at Black Widow AV.

I'm sure other folks have experience with the equipment you are using and can chime in.

Good luck,
Bill
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Old 03-07-2004, 09:07 AM
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Default RE: Dropouts with 200mw 2.4Ghz...

With a 1.2GHz system like you describe I was able to reduce the drop-outs by building a "patch" antenna tuned to the frequency of the camera/tx (for the recieve side). If you do a search on patch antennas you can find instructions, it just takes a couple of chunks of sheet metal, a connector and some soldering. I have to agree with ybnormal that the best way to greatly improve quality is to go with a CCD based system with more legal power. I am now using a 2.4GHz 200mw system with a CCD camera and get no drop-outs and much higher quality video (CCD vs. CMOS camera). It costs a bit more, but for me it was worth it. Most of the ebay 1.2GHz units operate with less than 50mw of RF output (they quote input power rather than output power).

Good luck.

Steve
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Old 03-07-2004, 12:10 PM
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Default RE: Dropouts with 200mw 2.4Ghz...

Unfortunately, what you have there is the absolute low end system. I know because that is what I started with.
The only thing you can do to improve that system is to hang the rx up as high as you can get it to get that antenna up in the air. You do not want anything to get between the two antennas as 1.2ghz does not like traveling thru bodies, plants, trees, etc.
The best way to tune in the signal is to remove the rx antenna, tune the knob VERY slowly till you get the best signal then replace the rx antenna.
Oh yeah, you can build one of those patch antennas. They do work very well.
Your next best alternative is to upgrade to one of those "800mw" Ebay systems that use a separate tx and cam. These can be had for what you paid for what you have now, generally a lot less, believe it or not.
DISCLAIMER: 1.2ghz is illegal to use in the US, especially the freqs those hongkong units use.
Chances of getting in trouble is probably nil tho. We have used the 800mw systems with good success. Check my website for "Grass Wired 2" video. That uses one of those systems.
I also have a comparison video that compares the system you have, one of the 800mw systems, an 800mw system with a better camera and a 900mhz (ham license required) system.

Now, if you REALLY want to do wireless video, cut to the chase and visit BlackwidowAV.com (plug plug plug!).
I have one of his 200mw systems and it rocks.
Shot this video using that:
[link=http://fubar1.freeservers.com/rc/movies/usbw1.wmv]Wired Ultra Stick 60[/link]

Broadband HIGHLY recommended.
ORIGINAL: loumorales

Can you help me get started? I bought a cheap @89.00 "spycam" video cam described in Quantum Hobbies as a good lightweight aerial cam (Perhaps cheap is my problem?). I got lots of dropouts with a few 5 second clear signals that made me itching to try harder. Can you suggest antenna or camera systems that work well? I have ZTV ELECTRONS Cam/TX, 50mw (cam and TX. in same little square about 1 inch on a side. (Tiny for cam and TX.) TX. has a 9volt pigtail. antenna is a 6" whip (thin wire) exiting the same 1" square. Pointing straight up. RX. is a 12volt, with a 6" "coiled whip? (thick) Pointing straight up. RX. has a fine tuning knob. System is 1.2 GHZ. Any advice would be greatly appreciated. Thanks.

Lou
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Old 03-07-2004, 01:19 PM
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Default RE: Dropouts with 200mw 2.4Ghz...

Thanks! As I've continued doing research I have found several things. I learned 1.2 GHZ is illegal (and I wrote about it so openly in my ignorance)! I learned that making a patch antenna although I'm told easy, would be impossible for me as I had zero success trying to understand some of the technical papers on antenna design (I do not have an engineers' brain...), and lastly, the Black Widow plug and play system you mentioned kept coming up in my reading! If I had a 3 year olds' description of how to make a 1.2 GHZ patch antenna I would try to make one, and then also buy the Black Widow system. Thank you for all the info.

Lou
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Old 03-08-2004, 08:38 PM
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Default RE: Dropouts with 200mw 2.4Ghz...

Actually, building the 1.2ghz patch antenna isnt that hard (and believe me I have posted a LOT about using 1.2ghz, by the way). I think the instructions are on RC-Cam.com or some such for a 2.4ghz patch antenna called the GPP antenna. All you do is double ALL dimensions given in the 2.4ghz instructions to make one for 1.2ghz.
OK, digging around I found the link for making the patch antenna:
[link=http://www.rc-cam.com/gp_patch.htm]GPP patch antenna[/link]
As I said, just double all dimensions given (including the air gap) and you will be in business!
I was about to make one but I ended up getting the Blackwidow gear and the patch antenna he sells instead.

ORIGINAL: loumorales

Thanks! As I've continued doing research I have found several things. I learned 1.2 GHZ is illegal (and I wrote about it so openly in my ignorance)! I learned that making a patch antenna although I'm told easy, would be impossible for me as I had zero success trying to understand some of the technical papers on antenna design (I do not have an engineers' brain...), and lastly, the Black Widow plug and play system you mentioned kept coming up in my reading! If I had a 3 year olds' description of how to make a 1.2 GHZ patch antenna I would try to make one, and then also buy the Black Widow system. Thank you for all the info.

Lou
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