Very Strange Thing Happening...

[Apollo11capcom]

So a couple of days ago I took the Evo out for a little flying, nothing fancy, just around the neighborhood. When setting up my video transmission settings (20, smooth is what I've found to be the most stable, 10 smooth is almost as good) I noticed once I set it to 20 there was a very distinct set of spikes showing on the graph. It almost had the appearance of an EKG heartbeat, all of the peaks were the same height, the wavelength was uniform, etc. It was almost like there was a beacon somewhere blipping away. I thought nothing of it, switched over to 10 instead and had fun until my batteries were all drained.

Well, today I went out in the country looking for someplace interesting and open to do a little filming. I found a nice open green field... the first green I've seen this season. I couldn't say no to that, so I pulled over, hit my hazard lights, and set up to film. When I got to the video transmission page and set to 20 Mbps, guess what I saw! Yes, the same spikes on the graph. About 8 of them, just like the other day in my neighborhood. How is that possible!? The only things present that were present the other day were the drone itself, my Jeep (although it was turned off both times, this time only the hazard lights were on), and me. Other than that it was a completely different area, no traffic, no towers anywhere, nothing.

What on Earth would cause that type of signal? I'm guessing it has to be the drone, but why and how would it be emitting a signal like that? Why just on 20 Mbps? It couldn't be the hazard lights could it? They blink rhythmically like the spikes show on the graph, but they don't give off RF that I know of. Any ideas?

 

[xspwhite]

I dont know the settings that you are speaking of, but did you check to see if your over exposure warning is clicked on?

 

[thomasr]

As for what you are seeing -- I would be almost certain this is the link established with the Evo -- it is the video feed and telemetry you are seeing "broadcast" -- and this would show up on the graphs as "interference". Because it is -- especially depending on how far you are from it. Even when that population is only Evo +1... lol

You can not see this graph without the Evo on -- but if you had a spectrum analyzer capable of monitoring 2.4 GHz spectrum in general -- you should see little to no interference with the Evo off -- and then it "heats up" spikes once the Evo is on.

The 5 and 10 settings are "not normal" but are acceptable for "some" wireless link configurations. The thinking here is that you are more able to "pierce" through the crowded 2.4 GHz spectrum with "narrower" channel widths. In theory it works, in reality YMMV.

This is why when you switch to 5 or 10 you do not "notice" the spikes -- you are not taking up such a "wide" part of the channels as using the 20 setting. It reduces your data link rate by choosing 5 or 10. That is why there are other options to select Smooth Normal - to cope with a smaller "channel width/pipe".

The 20 setting aligns the channels more into the Wifi "specs", so this is why you "may" notice a little more interference (more than your Evo) when around the general population. It will all have to do with you distance to the stronger signals being emitted by channels in use in these areas.

None of what I just said takes "terrain" into consideration nor does it take any spurious 1/2 or 1/4 wave emissions into consideration -- but it is rare to see this a problem in 2.4 GHz "usually." This is why FPV users had/have problems with 433 MHz controls and 900 MHz video links operating at the same time. The control was almost 1/2 the wavelength of the video link and that sometimes just does not work out well when antennas and other modules (transmitters and such) are not spaced out far apart enough. The signals can clash.

I am only speaking in terms of radio links, rates and emissions.

Edit. 2.4 GHz channels are usually 5MHz. There are only 11 to use in the US. This is why you see the different outcomes with 5/10/20 settings. Problems in the 2.4 GHz band being so crowded make things even worse if you have anyone around you utilizing a 40 MHz channel. They are practically causing problems for everyone else in their broadcast range.

This is also why you will see more problems around more "population" and of course less problems around very little to no "population." In these situations of dense population -- the band is still all jammed as all of the routers will be randomly spread out on every channel available. It just depends on how strong their emissions are in relation to path between you and the Evo.

 

[Apollo11capcom]

As for what you are seeing -- I would be almost certain this is the link established with the Evo -- it is the video feed and telemetry you are seeing "broadcast" -- and this would show up on the graphs as "interference". Because it is -- especially depending on how far you are from it. Even when that population is only Evo +1... lol

You can not see this graph without the Evo on -- but if you had a spectrum analyzer capable of monitoring 2.4 GHz spectrum in general -- you should see little to no interference with the Evo off -- and then it "heats up" spikes once the Evo is on.

The 5 and 10 settings are "not normal" but are acceptable for "some" wireless link configurations. The thinking here is that you are more able to "pierce" through the crowded 2.4 GHz spectrum with "narrower" channel widths. In theory it works, in reality YMMV.

This is why when you switch to 5 or 10 you do not "notice" the spikes -- you are not taking up such a "wide" part of the channels as using the 20 setting. It reduces your data link rate by choosing 5 or 10. That is why there are other options to select Smooth Normal - to cope with a smaller "channel width/pipe".

The 20 setting aligns the channels more into the Wifi "specs", so this is why you "may" notice a little more interference (more than your Evo) when around the general population. It will all have to do with you distance to the stronger signals being emitted by channels in use in these areas.

None of what I just said takes "terrain" into consideration nor does it take any spurious 1/2 or 1/4 wave emissions into consideration -- but it is rare to see this a problem in 2.4 GHz "usually." This is why FPV users had/have problems with 433 MHz controls and 900 MHz video links operating at the same time. The control was almost 1/2 the wavelength of the video link and that sometimes just does not work out well when antennas and other modules (transmitters and such) are not spaced out far apart enough. The signals can clash.

I am only speaking in terms of radio links, rates and emissions.

Edit. 2.4 GHz channels are usually 5MHz. There are only 11 to use in the US. This is why you see the different outcomes with 5/10/20 settings. Problems in the 2.4 GHz band being so crowded make things even worse if you have anyone around you utilizing a 40 MHz channel. They are practically causing problems for everyone else in their broadcast range.

This is also why you will see more problems around more "population" and of course less problems around very little to no "population." In these situations of dense population -- the band is still all jammed as all of the routers will be randomly spread out on every channel available. It just depends on how strong their emissions are in relation to path between you and the Evo.

I think i follow what you're saying, but of all the times I've flown the drone, its only shown the spikes the last two times. Ive flown it here in my neighborhood more than anywhere else.

I have thought of two other things that are different... im using a new tablet and Lifthor tablet mount. I need to try putting the tablet in airplane mode (or at least turning off wifi) and see if it goes away.

 

[thomasr]

I think i follow what you're saying, but of all the times I've flown the drone, its only shown the spikes the last two times. Ive flown it here in my neighborhood more than anywhere else.

I have thought of two other things that are different... im using a new tablet and Lifthor tablet mount. I need to try putting the tablet in airplane mode (or at least turning off wifi) and see if it goes away.

I did an interesting test with the Evo and having my phone on 2.4 GHz and 5.8 GHz WIFI... and was connecting to my home wireless. @Ansia and I discussed using WIndows 10 and MirrorShare to get the image from your phone/tablet screen to a bigger display.

The 2.4 GHz graph looked horrible. I know this had some to do with close proximity with everything close together - even if the WIFI is only ON but not connected -- your phone or tablet is still scanning channels and putting out emissions...

This correlates better with spikes you may be seeing -- especially being out further away from potential interference.

 

[thomasr]

I think i follow what you're saying, but of all the times I've flown the drone, its only shown the spikes the last two times. Ive flown it here in my neighborhood more than anywhere else.

I have thought of two other things that are different... im using a new tablet and Lifthor tablet mount. I need to try putting the tablet in airplane mode (or at least turning off wifi) and see if it goes away.

Make sure your Bluetooth is off also -- or that you don't have any other BT devices on and around. Its not common to see much interference since BT is so low powered -- but it can happen since BT shares the same frequencies: 2400 to 2483.5 MHz including guard band 2 MHz wide at the bottom end and 3.5 MHz wide at the top.

Of course as you mention -- airplane mode -- will solve signals coming from both at the same time.

 

[Apollo11capcom]

I did an interesting test with the Evo and having my phone on 2.4 GHz and 5.8 GHz WIFI... and was connecting to my home wireless. @Ansia and I discussed using WIndows 10 and MirrorShare to get the image from your phone/tablet screen to a bigger display.

The 2.4 GHz graph looked horrible. I know this had some to do with close proximity with everything close together - even if the WIFI is only ON but not connected -- your phone or tablet is still scanning channels and putting out emissions...

This correlates better with spikes you may be seeing -- especially being out further away from potential interference.

Yes, this is a good point... much like when a PC sends out a dhcp discovery packet, I bet it does the same thing looking for available wifi. Strange that I haven't seen it from my phone when I'm away from home, but I'm betting that's what it is. I'l know for sure when i get enough time to test it out.