Receiver lockouts at FF15

RAM

Posted a thousand or more times
One thing you could do is put up a poll asking pilots what radio equipment they used and whether or not they experienced problems.
 

ZoomNBoom

Senior Member
One thing you could do is put up a poll asking pilots what radio equipment they used and whether or not they experienced problems.

Thats the wrong approach; maybe those DJI phantom pilots with 2000mW 2.4GHz FPV boosters didnt suffer problems themselves, but what you really want to know and avoid is which pilots are very likely to cause problems for others.

Of course, they probably dont know, but there is a reason the ETSI directive was updated recently and that reason was precisely to dramatically reduce the chance for compliant hardware to cause such problems in crowded RF environments. Why not use that as a guideline?
 

jhitesma

Some guy in the desert
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Maybe to find a downed FPV plane? StoneBlue Airlines had a video about how to use an SA to find a down craft by searching for the video transmission.

He might have been. I just happened to hear "What the heck is that" and then a familiar voice saying "It's a spectrum analyzer" then glancing over to confirm it was the voice I thought it was :D I was knee deep in soybeans looking for plane bits myself at the time. I wanted to go checkout his setup later on but never found time.

But I wouldn't be surprised if he was doing some spectrum surveys as well. I know if I had the gear and was there I would have been just out of curiosity :D Though as busy as those guys were I can see him not having time to even if he wanted to.
 

Craftydan

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That seems to be why a lot of people are now using LHCP antennas. Less chance of interference from someone on same frequency in the area. LHCP seems to be not as popular right now..but I do see a lot more people on youtube with the LH antennas. Only a matter of time befor LH antennas are as popular as RH.

I hate to say it, they're far more common than you think. If you're using the cheap antennas it's likely LHCP -- Most of the cheap Chinese antennas are LH by default.

And yes, the Spec An that Alex was wandering the field with was to find a live video signal from a downed airframe. It's a tool of his trade, so no surprise he has one.
 

razor02097

Rogue Drone Pilot
I hate to say it, they're far more common than you think. If you're using the cheap antennas it's likely LHCP -- Most of the cheap Chinese antennas are LH by default.

And yes, the Spec An that Alex was wandering the field with was to find a live video signal from a downed airframe. It's a tool of his trade, so no surprise he has one.

well that sucks :( I was thinking about trying some ibcrazy airblades for that reason but maybe will do some more research.

I use immersion/fatshark RHCP antennas currently.
 
I did not experience any receiver lockouts.

I was using the following equipment:
Transmitter - Spektrum DX8
Receiver1 on helicopter - DSM2 (Spektrum SPMAR6100EB)
Receiver2 on airplane - DSMX (Spektrum SPMAR6210) satellite antenna not installed.

My brother experienced some erratic behavior; not sure it was attributed to receiver lockout. He was using the following equipment:
Transmitter - Spektrum DX6i (DSM2)
Receiver - whatever is included inside the E-Flite Blade 350QX.

Both of us were flying on the far end of field in the multirotor section.
 

Balu

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I can confirm Alex used a spectrum analyzer to find FPV aircrafts - at least once. Because I helped him find his tri this way :).
 

pressalltheknobs

Posted a thousand or more times
Thats the wrong approach; maybe those DJI phantom pilots with 2000mW 2.4GHz FPV boosters didnt suffer problems themselves, but what you really want to know and avoid is which pilots are very likely to cause problems for others.

Of course, they probably dont know, but there is a reason the ETSI directive was updated recently and that reason was precisely to dramatically reduce the chance for compliant hardware to cause such problems in crowded RF environments. Why not use that as a guideline?


"Wrong approach." is too strong. This would still be useful and better that just anecdotal reports. It would just be incomplete for the reasons you state. However it may show for example that most of those that had failures were using older less resilient protocols or perhaps specific protocols. This would be expected based on our existing bias and people can at least be warned as to what works and what tends to fail with some data to back that up. Or it could show that was not significant. If it was not then we can infer outside interference as a possible cause or that the newer protocols are not as good as we think. That would imply a more in depth study is worth pursuing - spectrum analyzers and the like.

One other point. I wonder how many people using Spectrum DSMX transmitters with DSM2 receivers believe they are running DSMX. Unless you have DSMX on both ends you are still using DSM2. As far as I can tell only the OrangeRx R615X claims to be true DSMX. The rest are DSM2/DSMX compatible but since they don't claim to be true DSMX are actually DSM2. Lemon makes quite a few rx's that claim to be true DSMX but they still sell a line of DSM2 receivers. This may account for the anecdotes that claim Orange and Lemon are "not as good as true Spektrum" because most of the Orange and many of the Lemon RXs are DSM2 and therefore more prone to failure.

The problem with DSM2 as I understand it, is that it chooses two channels for redundancy and sticks with them. This is ok if the two channels it picks are far apart but it seems (unless they fixed it) that it sometimes picks two channels that are close together. This makes it more likely that it will lose both channels at the same time given the same interference
 

thenated0g

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didnt read thru the entire thread, but i was wondering if having 1000 cell phones with wifi (2.4) on had any impact.
 

Craftydan

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Cell phones, probably not. They don't use anything on the 2.4GHz band in the US.

Wifi . . . well that's another story . . . but I think the *MANY* Aircraft transmitters would have a more significant impact than a potentially overpowered wifi router that may or may not have existed at our benevolent host's residence.
 

thenated0g

Drinker of coffee, Maker of things
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strange i know my phone has 2.4 and 5hz on it as do many new phones. Most non techy users that i know dont ever turn off wifi on their phones. Reason i was asking was i remember on my DJI f450 it was pretty adamant in the instructions about making sure your wifi was turned off on your phone before doing anything.
 

Craftydan

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Ah. Right. Many smartphones do have Wifi radios on them, but if they're not connected, they're generally not transmitting and adding to the overall noise. There are Cellphones networks that run their primary link back to the tower across 2.4, but not in the US.
 

thenated0g

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Not trying to be argumentative here. We have a club meeting coming up this Friday. For the national Model aviation day we had a lot of people on site and this topic came up and i would like to talk about it for future events. From what i can see the 2.4 range of frequencies is exactly the same for both wifi on your phones and RC models. Now maybe the technology doesn't allow interference, but it seems plausible to me that having over 1000 cell phones and several hundred 2.4 rc planes in the sky could very easily use up that very limited range. Again, i don't know much about this from a design standpoint. But i do setup 2.4 and 5 bridges for work and i know that if you get close enough to a powerfull transmitter it can totally blow out your signal even on different channels. I was just thinking that maybe at pilot meetings and when guest come, as a "just in case", tell everyone to turn off wifi on devices.

wifi frequencies: https://en.wikipedia.org/wiki/List_of_WLAN_channels
RC frequencies: http://www.modelaircraft.org/events/frequencies.aspx

both go from 2.4 to 2.485
 

thenated0g

Drinker of coffee, Maker of things
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actually i would argue that it may be worse with no connections. They are all looking for a AP to connect to and with all the noise from the other phones may be turning the power up to talk above the noise floor.
 

thenated0g

Drinker of coffee, Maker of things
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again not trying to argue at all. I am just getting excited about ffwest and reading about these lockouts is sad. be nice to avoid this in the future.
 

razor02097

Rogue Drone Pilot
Can I just add that my phone (and many others) have the hot spot feature in which the phone acts as a modem/wifi router. It's range is pretty limited... more than about 20 feet and the signal completely drops out. Also in general the wifi routers aren't going transmit a lot of data unless people are downloading huge files or streaming video...but the amount of data that eats would typically make that fairly prohibitive.
 

Craftydan

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I understand what you're saying -- this is about the right answer, not who's right ;)

. . . and I learn something new every day . . .

So from looking deeper into the protocol, the answer is yes and no.

Most devices do actively scan for a broadcasting client once per channel (I didn't know that), ironically, in the neighborhood of 25 to 50hz (a bit slower than most of our radio's update rate). While they can scan passively, that mode is about 4 times slower, so the devices will kick on their transmitter in active mode for short bursts when you ask to find hotspots in the area -- it's not quite evident if they stay "active" if you aren't seeking these connections, and the answer appears to depend on how the device is programmed.

So Yes, there will likely be more traffic with a room full of smartphones with Wifi turned on but disconnected than if the wifi is turned off. By how much would depend on how the devices are programmed.

. . . but . . .

Wifi in general practices CSMA/CA (carrier sense multiple access with collision avoidance) -- a big mouthful to represent "how I keep from stepping on other wifi radios I can't hear, but are in range of a router". Effectively, before any wifi radio transmits, it listens. If it can't hear anything, it then sends a brief burst . . . and stops. How brief is this burst? depends on the bitrate -- the probe request is 2 bytes long and at a 2Mbps rate (which is a typical slow rate) that's roughly 1 microsecond . . . every 20-40 milisecond, and only if it doesn't hear something first. That's a duty cycle of 0.005% to 0.0025%. Larger packets (like big chunks of juicy data) take much longer, but if you haven't connected and there's nothing out there to connect to, your packets don't get any bigger.



Long story VERY short . . . it would take MANY (thousands) cellphones packed within a small area to deny access to 2.4GHz to a non-cooperative RC transmitter/receiver pair. Now if there's a high capacity public wifi hotspot available within range . . . all bets are off.

How many control transmitters would it take? Regardless of the frequency hopping scheme, I doubt they can share the band between thousands of them . . . but you'd need to know the bitrates of each to be accurate.
 
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Balu

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Long story VERY short . . . it would take MANY (thousands) cellphones packed within a small area to deny access to 2.4GHz to a non-cooperative RC transmitter/receiver pair. Now if there's a high capacity public wifi hotspot available within range . . . all bets are off.

If you see me fiddling around with a microwave shortly before a combat next year, just ignore that...