FPV video cutting out at 50-100m

[huioliver]

Hi,

I'v recently installed a 5.8Ghz 400mW FPV video set onto my Quad, with circular polarized antennas.
As I take off and start to fly, everything is working fine, picture is good and clear, until I get to about 50-100m the video goes fuzzy and cuts out rather suddenly.

Here is the setup:



TBS Frame
TBS 750kv motors
4S 3700mah battery
DJI Naza-M-V2 flight controller
FrSky 2.4Ghz diversity receiver
Mobius Action Camera on a pitch gimble mount
DJI iOSD mini
5.8Ghz 400mW Tx and Rx set from foxtech with Boscam circular polarized antennas from hobbyking.
Tx is being powered by a $7 "UBEC" from hobbyking that outputs around 12v

The "ground station" is quite simply a 2.4Ghz FrSky Taranis with an 8" screen from hobbyking mounted on top with the receiver mounted to the back of the screen, powered by a 3s battery that is charged to put out no more than 12v.

So anyway, at first I thought just maybe the Tx was getting interfered with from other components on the Quad, or getting pounded by vibrations from the frame and propellers, so I put a tin foil kinda shield around it and used anti-vibration foam to mount it, did nothing. I also thought it was most likely the receiver getting interfered with from the local area, so I moved further away from any houses/power supply systems, nothing changed. I also tried getting someone to hold the receiver up and away from the screen and transmitter, no better... I tried using the stock linear antennas and was still no better.

What do you reckon is going on? Bad products? I'm not fixing those suspected problems the properly?
You might need to know that I'v noticed the receiver gets very warm during use, warmer than the transmitter and even the motors, not normal?

Hope its nothing too complicated, but it always is... Thanks for reading.

[xxpitt]

Hi huioliver,

Sorry to hear your having some problems. You should be getting much further than 150m, atleast a km i would say. Have you tried switching channels? Receivers don't usual get warm so it could be faulty. Do you know anyone else who flies? You could tune into one of their flights see your signal fades out much earier than theirs. That would tell you it's probably your rx. Or you could use there goggles monitor to fly then if your still getting short distances it's your vtx side of things

[bigMouse]

couple of things!

The boscam rx's that I've seen does get warm especially if you run them on 3S (they have an internal v reg that causing the heat)

Are you absolutely sure tx and rx is on the same frequency? Did you buy them as a pair?  Some different bands have overlapping channels, which will produce video close up but soon drop out with a small distance.

Check the antenna plugs and sockets on the tx and rx, one side should have a central pin, no central pin and the antenna won't work!

Lastly be worth checking the output power of the vTx, no power meter then try your tx then rx by substitution with a friends gear, No friends then a power meter can be really handy!

http://www.hobbyking.co.uk/hobbyking/store/__62581__ImmersionRC_RF_Power_Meter_And_30dB_Attenuator_35Mhz_5_8Ghz_UK_Warehouse_.html?strSearch=power%20meter

[huioliver]

Aaaaah it was the channels! I did buy them as a pair and took one look at the channel switches and thought, ahh yeah they're all in the up position, should be fine. Turns out the Tx was actually all in the down position. So I adjusted them to the same channel, took it for a fly straight away and it flew heaps further without cutting out. Yay!

Thanks heaps you guys!

I can get to tidying up the rest of the Quad now that thats off my mind, am going to redo the camera mount with hardwood rather than cardboard, to help with vibrations, cause its quite bad at the moment. But yeah now I got another, only small, problem. It can only fly for 8 mins. I guess I can put up with that for now. But as soon as i'v got more money spare i'll upgrade the motors/arms/battery.
Also that RF power meter does look quite useful.

Thanks again. Maybe soon i'll be sharing some videos!

[xxpitt]

What size lipo do you have? I used to fly a 3s 4500mah lipo and get around 12 minutes on 10 inch props. Then I went 4s and dropped to 9 inch props because i wanted to do more stunt type flying and my times dropped to about 8mins, but that was always near full throttle. You have lower kv motors than I had so you should in theory get  longer flights try putting largest props that will fit on maybe 11 inch if they fit or even bigger. I wouldn't switch motors till you've tried other props. 750kv is an ideal kv for the tbs discovery that wants longer flight times. larger props would be my 1st suggestion it's also the cheapest option. I always had jello problems with my video on the disco too. I even got the tbs love seat and still got jello on my go pro. try putting some foam between camera and the frame to dampen vibrations

[huioliver]

I use a 4s 3700mah, weights about 410g. Didn't think of the propellers, makes sense tho, I will try larger props for sure then! I'm currently using 9 inch props, and are already very close to the rear antennas, so will have to move them or do something to fit bigger ones.
These ones seem alright? http://www.hobbyking.com/hobbyking/store/__25690__Carbon_Fiber_Propellers_11X5_LH_and_RH_Rotation_Pair.html

I have 2 layers of anti-vibration foam underneath the cam. I read somewhere that the more stiff you make the parts, the more effective the foam will be? The cam where it is now, seems quite wobbly and all. The cam's recording's not only look a tiny bit fuzzy and jelloy, but the audio has a very load buzzing sound when the motors get up to speed. I noticed this goes away when the cam is pitched down. Someone told me that it could be the propeller's air turbulence from the tips hitting the the cam and mic.

[xxpitt]

They'll be ok if they can fit. Maybe 10 inch is the largest that will fit. The dji arms are quite flexible so i think they can amplify the vibrations. That's why I didn't like the tbs discovery very much. For the price it should be a vibration free machine. Even my cheap chinese mini frames produce better video. have you balanced your props also? Does go a long way to better video

[bigMouse]

That's why I didn't like the tbs discovery very much. For the price it should be a vibration free machine.

For the price it should be solid platinum...


huioliver, Need some experimentation, 750kv should be fine for up to 10X5 props and should be ok for up to 4S. any bigger then you would probably need to change the motors for lower kv

[xxpitt]

i would increase your lipo size also, like i say i had 4500mah with 980kv and 9" props with 750kv and larger props youu would be able to lift a heavier load more efficiently, i would be tempted to go 5000mah if one fits in battery bay

[huioliver]

After measuring there is no way 11 inch will fit on that frame with the DJI arms anyway. The propellers would hit each other. I built this quad from money I saved up from a job I had for about a month, until the business went broke... So I don't have any job and quite seriously cannot afford much more than some 10 inch props and a prop balancer. So i'll think about a bigger battery another day.

[xxpitt]

ah fair do's, 10inch will be fine, balancing props should go along way towards getting rid of jello, but its no easy task on the tbs discovey, i had to balance props use a love tbs love seat with a memory foam inner sole between that and the frame, that was with a gopro shooting 60fps too. these issolation bobbins some of the minis use do a really good job though. if you could find a way to use them bet it would work a treat