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Thread: No luck with any vtx/rx products at all, please help

  1. #1
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    No luck with any vtx/rx products at all, please help

    Hi,
    I'm amazed to see so many people here getting usable video signals on here! I personally have been struggling to get even static most of the time. I've been flying an s800 and 3dr x8 for a while and from the get go there have been video transmission problems. I don't know how much more troubleshooting I can do before I get to the conclusion that I personally am the biggest source of RF interference on the planet and any radio frequency withing 5 miles of me will bend itself in knots to avoid reaching the receiver. I've used the stock DJI avl58 tx/rx with stock antennas and it doesn't matter if I'm in the city or 50 miles away from anything, the best signal I've ever gotten was in black and white and very noisy and disappeared after 50 ft (and in this particular instance the rx and tx were on completely different channels!) I've tried 3 or 4 different kinds of monitors. I've used whips, cp, and helical antennas and they are all equally bad. I've put the tx in as many different places on the craft as possible, or just hand held them to remove all interference. I've pointed my antennas every which way. I've tried running 5v fpv cameras that are supposed to work out of the box and got nowhere. I've used a mondo stinger/yellowjacket diversity combo, an immersion diversity receiver with 600mw 5.8tx spliced into the DJI osd via the avl58 cable, 3dr's tx/rx fpv system, and I've got a bighead fpv monitor with a built in diversity receiver. None of them will give me a picture I can use, and any signal I do get is gone after I leave my 50 ft maximum range. So at this point I have no idea what to try fixing because nothing I've tried has improved anything. All of my aircraft came with 5.8 setups and I'm not thrilled about the prospect of switching to another frequency but I'm seriously considering it. I've heard about people getting the range I need out of 5.8 but my experience has made me wonder whether you're all lying or just crazy. I'm not even trying to fly fpv, I'm doing professional AP work completely blind and getting lucky enough with my framing, but I need the other people on the ground to be able to see what I'm pointing at without having to playback from the camera when we land. I've been poring over every forum out there and pouring more money than I should be on gear to test out but it's not going anywhere. All of your advice...please.

  2. #2
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    Where are you located? We need pictures and more information to be able to help.

  3. #3
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    Quote Originally Posted by girthquake View Post
    I've used the stock DJI avl58 tx/rx
    That's a big problem, they don't work well.

    Wayne
    Everybody loves a bunny.

  4. #4
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    Quote Originally Posted by Beachflyer View Post
    Where are you located? We need pictures and more information to be able to help.
    Yeah I've been really frustrated with it for a while, which is what led me to try so many things to get a better result but nothing has worked any better for me so far.

  5. #5
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    Quote Originally Posted by Beachflyer View Post
    Where are you located? We need pictures and more information to be able to help.
    I can put up some pictures in the next couple of days. Usually I'm flying around thensan Francisco bay area, in the hills a couple of miles away from anything, in parks, but I've flown in some pretty undeveloped places without much in the way of any other signals around to speak with the same problem. When I don't have the opportunity to take my gear somewhere that remote and test it I'm working on it in a concrete warehouse building in San Francisco with plenty of interference around. It can't be so crowded that with two separate sets of transmitters and receivers don't get anything but static though, right?

  6. #6
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    Asked for location as there may be someone experienced near you that could help.
    With the limited information, my guess would be a cabling or equipment compatibility problem.

  7. #7
    Size matters c5galaxy engineer's Avatar
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    I think CaliDave on here would be your best bet. He is in your area and a pretty smart guy. PM him and if he cant help you then he will know someone who can. They have a pretty good group in your area.
    Brett Hays
    JosephOregon.com
    flitetest.com/articles/fpv-full-scale-cockpit-ground-station-w-42-tv

  8. #8
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    It sounds very much like you have either horrific crosstalk among the wires in your rig, something in your rig or on your person is spewing out interference in the 5.8ghz frequency band or you are having a channel mismatch problem. While the DJI 5.8 unit isn't the best, you should get more than 50 meters out of it. The fact that you have tried both the Yellow jacket and the Immersion Vtx combos tells me that it isn't the Vtx that is at issue. I think we need to back down and start from the beginning here:

    1. Try different channels on your Vtx and headset. Make sure that the receiver and the transmitter are both on the exact same frequency and not on "nearby" frequencies with the same numbered channels. The "nearby" problem can cause EXACTLY the issue you are having. Fair reception up close that rapidly dwindles in a very short distance. Refer to the channel charts for your gear. Airwave module based gear like the Immersion and Fatshark gear doesn't play nicely with Boscam module based gear that uses a slightly different frequency sets. See HERE for a chart.

    2. Make sure that you are not carrying anything on your person, in the immediate vicinity or on the craft that radiates on the 5.8 ghz frequency other than your Vtx. This includes cellphones, bluetooth earpieces, some car stereo systems and some models of GoPro camera. If any of those radios are even ON (doesn't matter if they aren't connected to anything) than that can hose your video signal on either 5.8ghz or 2.4ghz

    3. Ensure that the RF environment onboard your craft is as quiet as possible. You want to be sure that you have no "ground loops" in your system, and that all of the wires are twisted or braided. The Vtx/camera should also have an LC filter between it and anything else on the craft. If you have any long servo runs or REALLY want to quiet your system, consider picking up some CAT6 STP cable and soldering it in place of the servo wires. (Cut the heads off of the servo wires and solder them to the CAT6 wires, or get a servo wire building kit and directly attached new servo heads.)

    4. Having a good RF tester helps too when attempting to determine the source of RF interference, however I don't think any offer scanning in the 5.8 ghz frequency.

    5. Check out the area you will be flying with http://www.antennasearch.com/ to get an idea of what the RF environment will be and to see if there is anything around that spews on 5.8 (unlikely, but the link is still a good one to have handy)


    Honestly, I suspect that #1 or #2 are the most likely sources of your problem.

    Good Luck!
    [FONT=Palatino Linotype][SIZE=3][I][B]FPV - The World is My Airfield[/B][/I][/SIZE][/FONT]

  9. #9
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    Any chance you were running the VTx without antenna at one point? That usually kills them quickly.

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