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RC interferance
116 5 2017-4-18 06:24:32
Ralphhuttonthom
Beginner
Canada
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I have a contract to do aerial photography in a stadium, just before the  game. Potentially 20K people in the stands all flashing their smart  phones around, all seeking a WIFI connection on 2.4 GHz (the RC control frequency of the Inspire). I have to get Transport Canada (TC) approval which should not  be too difficult because I have a good track record with TC.

My question, is it safe to fly the Inspire only a distance of 200 to 300 feet from the RC, full VLOS at all times in an environment with thousands of WIFI equiped cell phones all seeking the same 2.4 GHz frequency? My concern is that the smart phones will all be automatically  seeking 2.4ghz WIFI connections or maybe even have Hotspot turned on. I understand that the  RC/Inspire connection is encrypted so wouldn't this negate any possibility  of interference? I do leave the RC settings to allow automatic channel swopping, I prefer to leave that alone. I have noted the big difference and big variations in channel strength using the Go App as part of my standard checklist.

If radio interferance does cause the RC link to be broken, I assume the worst that can happen is that the Inspire triggers RTH?

Is there any chance someone could take over control of the Inspire thereby potentially causing a very dangerous and embarrassing situation.

2017-4-18 06:24:32
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Donnie *
First Officer
Flight distance : 862765
United States
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If I were you I would be doing some testing to see what the interference could be , bring you system to a crowded stadium and  fire up the system without  the props and see if you have any issues , vary the range etc.  I dont think anyone is going to take over your system but a RTH sounds like a possibility .   I would use a zoom lens to make it look like you are closer than you are to people .  I would avoid flying over people as much as possible if not entirely and use some perspective tricks to get the shots you need.

Also you should have a channel spectrum analyzer to check the frequencies being  used in that environment and also you may wish to have prop guards installed as well just in case , I think I would be more comfortable with flying say  a Phantom  4 it is much smaller and has  less impact damage if something fell from the sky , also the Mavic has prop guards that prevent any  fingers from people trying to grab it .  

This is a risky venture as there are so many variables , could you not get the same effect from say a RC blimp that is less apt to fall from the sky ??  I have NEVER had any problems with my system but I have seen it happen.

By the way , the Image transmission is the only thing you have any control over as far as the channles are concerned , I personally would  lock on to channel 20 as there is NO WI fi on that channel at all.    Likle I said I would do some test runs and  invest in a channle spe ctrum analyzer , and then compare to the frequncy chart .  Member Daroga had a good chart on that and I will try to find it .  

Just my 2 cents .

donnie
2017-4-18 11:33:00
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Donnie *
First Officer
Flight distance : 862765
United States
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Here is a good link to identify frequency , good luck .

https://docs.google.com/spreadsh ... li=1#gid=1477125990
donnie
2017-4-20 08:02:54
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Ralphhuttonthom
Beginner
Canada
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Thanks for your thoughts Donnie, agree with you but I am a super cautious person so will have to give it a lot of thought along with tests and dry runs before going ahead. But I am not a radio engineer so a couple of questions;
1. I assumed when I look in the Go App at that HD Image Transmission settings was analyzing the spectrum used by the controller and the image transmission (since they are both using 2.4 GHz). I read that it multiplexes somehow? I understood this is an effective spectrum analyzer and that spikes on -60 db or more mean problems.
2. wouldn't the automated channel hoping just settle on channel 20 if there was interference on the the other channels?
The spreadsheet looks interesting I will have to study it to see if I understand it fully.
Thanks again for your input.
2017-4-20 09:44:13
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Donnie *
First Officer
Flight distance : 862765
United States
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Ralphhuttonthom Posted at 2017-4-20 09:44
Thanks for your thoughts Donnie, agree with you but I am a super cautious person so will have to give it a lot of thought along with tests and dry runs before going ahead. But I am not a radio engineer so a couple of questions;
1. I assumed when I look in the Go App at that HD Image Transmission settings was analyzing the spectrum used by the controller and the image transmission (since they are both using 2.4 GHz). I read that it multiplexes somehow? I understood this is an effective spectrum analyzer and that spikes on -60 db or more mean problems.
2. wouldn't the automated channel hoping just settle on channel 20 if there was interference on the the other channels?

Regarding question 1 =The control of the AC is not Programmable ,( so it is always channel  Hopping  in smaller  value Mhz )  You cannot choose for example channel 17 for control of the AC .  Only the Image Transmission is programmable if you wish .  I dont know for  100% sure what value of  db gives issue with the system .

Q 2 _Sure it would if it thought that was the best channel , I just find from experience that this is the best channel for doing my long distance flights , etc.

The spreadsheet is interesting and I am still digesting it myself .
I have a lot to learn on this as well !

donnie

2017-4-20 10:33:28
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Ralphhuttonthom
Beginner
Canada
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Thanks Donnie
A fellow on the InspirePilots.com forum (Scotflier I think) suggested getting a RF Explorer and Handheld Spectrum Analyzer model WSUB1G 240 or similar and had said -60db would indicate quite bad interference. I've never had a disconnect but using Healthy Drones I did have some poor signal indications and when I looked at the detailed logs it showed dropped data. I did upgrade to the iPad Pro 9.7 (cellular) at the recommendation of Autoflight Autopilot team which made a big difference (having much better computing power). Not sure if the last point has anything to do with the RC/Inspire staying connected.
Thanks again.
2017-4-20 14:00:19
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