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Old Jun 05, 2012, 03:41 PM
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Kahuna717's Avatar
United States, TN, Greeneville
Joined Oct 2010
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Help!
Terrible problems with 1.28GHz video interfering with UHF Equiptment!

Hello all,

I have been experiencing a lot of problems with my Dragonlink UHF system receiving interference from my Lawmate 1.28GHz 1000mw vtx.

First let me tell you a little about my setup:

The Dragonlink RX antenna is mounted on one wingtip. The two wires are mounted at 180 degrees perpendicular to the ground. The RX antenna wire runs along the wing then goes into the fuselage of the easystar; where it connects to the Dragonlink receiver.

The vtx is mounted on the OPPOSITE wingtip of the Easystar. It uses the stock lawmate antenna. In addition TWO ferrite rings have been added to the wires going into the vtx. They have a total combined number of wraps of about 17 wraps through the ferrite rings.

The camera I use is the $17 hobbyking CCD camera mounted on a pan and tilt mount. The wires going to it have also been wrapped through ferrite.

I have the option of pluggin in my EzOSD whenever I want to my system. The RSSI from the Dragonlink Receiver is connected to the EzOSD.


Now let me tell you about the problems I'm experiencing:

With the DL (Dragonlink) TX turned OFF and the vtx ON I get anywhere from 0-35% rssi strength. Random numbers between those two show up constantly.

When I power on the DL TX with the DUMMY LOAD and vtx OFF I can go almost 70 feet before my plane goes into fail safe. However when I turn the vtx ON that distance is more than halved. I can only go about 20 feet before i fail safe.


My question is WHAT'S NEXT!?!? I have considered adding a low pass filter to the RX of the Dragonlink to see if it will filter out the 1.28GHz noise.

I have also considered just selling my 1.28GHz Equiptment and starting over with 2.4GHz lawmate stuff.

I have even thought about adding a booster to my DL system and pick up about a 2 watt boost. Hoping to overpower the interference.


This interference has already caused 2 failsafe crashes at less than 2 miles with my setup. I am now scared to death of flying my system, which is something that should not be happening!


I'm attending the "2nd Annual Southeastern FPV Meet" up in Georgia this weekend and I hope to ask for help there.

Any help you knowledgable folks could offer will really be appreciated!

Thanks!
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Old Jun 05, 2012, 03:48 PM
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Illinois, USA
Joined Aug 2009
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When your powering up the Video TX are you also powering your camera? What else? I never really had a problem with the VTX interfering with UHF. It may be an additional component causing the problem.
The best method to determine is power up the DL system then range check with dummy load then add back one component at a time. Sounds like your on the right track though.
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Old Jun 05, 2012, 03:52 PM
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Lakewood, Colorado
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Is it some ancient version of DL (very earliest versions had limited filtering), because a current DL
system is not affected by 1280Mhz video gear at all. I did a range test where I placed my
DL Tx on a tall hill on one side of town (greater Denver metro area) and drove all the way to the
other side with my FPV plane in my car, all gear powered up, including 600mW 1280Mhz video
Tx, while the RC Tx cycled all the servos and still had control out to 36 miles.
My DL Rx antenna and 1.3Ghz video Tx antenna are about a half wing span apart.

I think you need to focus elsewhere. Maybe other sources of UHF noise (like
the cheap camera for instance). Your baseline dummy load range test seems
a bit low, but not all terminators are equal.

ian
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Old Jun 05, 2012, 03:58 PM
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odds are, the 1000MW TX is just spewing RF all over the place, not just from the antenna.

I would try a high pass on the 1.28ghz TX. an SHP-1000+ should work:

http://www.minicircuits.com/products...oax_high.shtml

.4DB loss at 1280, 57DB loss at 400.

there is a possbility that the RF is coming from something else though. Perhaps even the camera. Maybe from the VTX CASE even. I think the filter is a good bet, anyway.
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Old Jun 05, 2012, 04:08 PM
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I can count the number of people I've ever heard complaining about 1.3Ghz video Tx interference
to their UHF Rx on one finger. Unless the VTX is damaged in some way, I doubt
very much that it is the source of the problem. The most likely culprit is the camera.

ian
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Old Jun 05, 2012, 04:10 PM
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United States, TN, Greeneville
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Quote:
Originally Posted by vertcnc View Post
When your powering up the Video TX are you also powering your camera? What else? I never really had a problem with the VTX interfering with UHF. It may be an additional component causing the problem.
The best method to determine is power up the DL system then range check with dummy load then add back one component at a time. Sounds like your on the right track though.

When I power my VTX the only thing I power besides it is the camera. The rest of the plane is on its own battery. I will try unplugging the camera and see if that helps any.



Quote:
Originally Posted by Daemon View Post
Is it some ancient version of DL (very earliest versions had limited filtering), because a current DL
system is not affected by 1280Mhz video gear at all. I did a range test where I placed my
DL Tx on a tall hill on one side of town (greater Denver metro area) and drove all the way to the
other side with my FPV plane in my car, all gear powered up, including 600mW 1280Mhz video
Tx, while the RC Tx cycled all the servos and still had control out to 36 miles.
My DL Rx antenna and 1.3Ghz video Tx antenna are about a half wing span apart.

I think you need to focus elsewhere. Maybe other sources of UHF noise (like
the cheap camera for instance). Your baseline dummy load range test seems
a bit low, but not all terminators are equal.

ian

It's one of the decently newer DL systems. I got mine like June of 2011. It's new enough to be black and have the slim receiver.




Quote:
Originally Posted by gundamnitpete View Post
odds are, the 1000MW TX is just spewing RF all over the place, not just from the antenna.

I would try a high pass on the 1.28ghz TX. an SHP-1000+ should work:

http://www.minicircuits.com/products...oax_high.shtml

.4DB loss at 1280, 57DB loss at 400.

there is a possbility that the RF is coming from something else though. Perhaps even the camera. Maybe from the VTX CASE even. I think the filter is a good bet, anyway.

Alright, I'll probably order one to try. I have also thought about reducing to a 500mw TX. Maybe 1000mw is just too much. Do you think a low pass filter on the DL receiver might help too? I got one of the guys bringing one to let me try at the meet I think.
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Old Jun 05, 2012, 04:11 PM
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Quote:
Originally Posted by Daemon View Post
I can count the number of people I've ever heard complaining about 1.3Ghz video Tx interference
to their UHF Rx on one finger. Unless the VTX is damaged in some way, I doubt
very much that it is the source of the problem. The most likely culprit is the camera.

ian
the more i think about it, the more i agree with you. Something it giving him 433 noise. I've never used the 1000MW 1.28's, but i have used the 500mw 900's and they are noisy.

I didn't have any problems with 200mw 1280 on my quad with DL.

However, i haven't heard much about that camera. He's talking about the HK one, correct?
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Old Jun 05, 2012, 04:12 PM
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Quote:
Originally Posted by Kahuna717 View Post
When I power my VTX the only thing I power besides it is the camera. The rest of the plane is on its own battery. I will try unplugging the camera and see if that helps any.

It's one of the decently newer DL systems. I got mine like June of 2011. It's new enough to be black and have the slim receiver.


Alright, I'll probably order one to try. I have also thought about reducing to a 500mw TX. Maybe 1000mw is just too much. Do you think a low pass filter on the DL receiver might help too? I got one of the guys bringing one to let me try at the meet I think.
a low pass on the DLRX would do similar, but i would elminate the source of the noise at the TX, instead of masking it at the RX.

That said, try figuring out exactly which component is causing you trouble. Could be the camera.
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Old Jun 05, 2012, 04:19 PM
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Quote:
Originally Posted by Kahuna717 View Post
When I power my VTX the only thing I power besides it is the camera. The rest of the plane is on its own battery. I will try unplugging the camera and see if that helps any.
I'll bet you'll find it's the camera.

Quote:
It's one of the decently newer DL systems. I got mine like June of 2011. It's new enough to be black and have the slim receiver.
There's a newer version than that, but the one you've got should not have any problems with
1.3Ghz video gear.

Quote:
Alright, I'll probably order one to try. I have also thought about reducing to a 500mw TX. Maybe 1000mw is just too much. Do you think a low pass filter on the DL receiver might help too? I got one of the guys bringing one to let me try at the meet I think.
Check the camera before any of this.


ian
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Old Jun 05, 2012, 05:12 PM
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Well guys, status update:

The camera is not the problem! I carefully watched the RSSI signal with the camera off and then plugged in the camera..RSSI didn't go up or down AT ALL!

Still looking for a solution I guess
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Old Jun 05, 2012, 05:15 PM
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can you give us some pictures? is there anything else on the plane? Gopro?

could be noise from the TX still IMHO.
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Old Jun 05, 2012, 05:21 PM
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I had a 500mw lawmate and found if using a circular polarized antenna it destroyed my UHF range. As short as 500m sometimes. I had a bandpass filter made up for it, all my RSSI returned, micro mode range tests were fine, took to the air and within 500m lockout
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Old Jun 05, 2012, 05:24 PM
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More testing results:

Once again the RSSI hasn't changed whether cam is turned on or not.

Also when the Dragonlink TX is turned off the RSSI is picking up about 30 RSSI but like a clock EVERY 7-8 seconds the RSSI drops to 8%. It never fails to drop every 7-8 seconds whether camera is turned on or not.

I'm working on finding a way to upload pics..I'm away from home (vacation) with my IPhone and i cant upload from Iphone. Brought the FPV gear with me of course.
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Old Jun 05, 2012, 05:33 PM
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download a photobucket or imgur uploader app from the app shot. Take on iphone, upload to imgur or photobucket with app, post here.
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Old Jun 05, 2012, 05:42 PM
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I am with Ian, Just power the VTX and not the camera or anything else and rerun the range test.
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