Author Topic: Unmanned Aerial Systems (UAS) interference  (Read 1223 times)

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Offline DanTheMan

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Unmanned Aerial Systems (UAS) interference
« on: June 17, 2014, 13:45:20 PM »
Have a look at this video https://www.youtube.com/watch?v=JNtNhDf5Xuo
It shows interference to the video rf from a cell tower.

Here is quite a popular uas , the Phantom 2 Vision : http://wiki.dji.com/en/index.php/Phantom_2_Vision
This uas is controlled over a 5.728 GHz to 5.85 GHz link using between 5mw and: 125mw. I'm not 100% sure if 2.4Ghz is for control or just the video relay ?

This is a theoretical question about interference. Imagine that the uas flew OVER Three Rock or within a couple of hundred feet of the Mullaghanish transmitter which has a number of transmissions ranging from 20 to 200 KW ! Would the uas lose it's communication link? If not why not?

thanks in advance.
« Last Edit: June 18, 2014, 00:18:55 AM by DanTheMan »

Offline vanmie

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Re: Unmanned Aerial Systems (UAS) interference
« Reply #1 on: June 18, 2014, 08:45:17 AM »
In todays standards, all equipment must be capable of withstanding external EMI/RFI. EMI is regulated to allow today's sensitive equipment to function properly without suffering degradation in performance due to interference generated by other electronic devices.

For IT equipment, including WiFi equipment operating on 2.4 GHz or 5 GHz, this is described in EN55022

so, the receivers used in those UAS devices must be capable of operating even when in close proximity of those transmitters you mention. The devices must have band filters to prevent overloading the front end of those receivers. When commercial available equipment is used it must already comply with the EN55022 mentioned. If homebrew is used, then the builder/maker must ensure these standards are followed.

The mandatory compliance is described in "EMC Directive 89/336/EEC"
Source: http://eur-lex.europa.eu/legal-content/en/ALL/;ELX_SESSIONID=JW8FThBP1hH90nGj3hVXWsvsJysFjhNL4V7jZymQmqd12z2LQdht!-694022248?uri=CELEX:31989L0336


Which states in "ANNEX III":

"
Apparatus, and especially the apparatus referred to in (a) to (l), should be constructed in such a way that it has an adequate level of electromagnetic immunity in the usual electromagnetic compatibility environment where the apparatus is intended to work so as to allow its unhindered operation taking into account the levels of disturbance generated by apparatus complying with the standards laid down in Article 7.
"

Conclusion: a properly constructed UAS as you mention would simply continue to operate in proximity of other sources of EMI/RFI

HTH,
Edwin.


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Offline vanmie

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Re: Unmanned Aerial Systems (UAS) interference
« Reply #2 on: June 18, 2014, 08:58:27 AM »
To answer specifically what happened in the video with the cell-tower:

Mobile/Cell towers should be compliant with the same Directive.
However I believe (without proof) that they are "pushing the limits" on allowable interference at the transmitter outputs of such towers.

One of the tests is to move your mobile phone close to a receiver (a normal FM radio clock in your bedroom will do)
then call your mobile phone using a land line.

Just before the mobile phone rings, you will hear interference thru the speaker of the FM radio... the radio does not even have to be turned on !!!

This is due to the enormous burst of power the tower will use to initiate the "link" to your mobile phone.

I question if this "burst" is in line with the ECC/EMI Directives... and this is probably what the video is showing; interference due to high-power-bursts

(this is my opinion; so this is open for discussion)

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Offline 5566

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Re: Unmanned Aerial Systems (UAS) interference
« Reply #3 on: June 18, 2014, 09:12:19 AM »
Oh, any decent flying model nowadays is fitted with a GPS module what would safely bring the thing into the control. No rocket science involved in it.

Offline martins

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Re: Unmanned Aerial Systems (UAS) interference
« Reply #4 on: June 18, 2014, 17:04:11 PM »
how do we now that this loss of signal is caused by interference? usually when bumps make broken things suddenly work, it's a loose connection

Offline vanmie

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Re: Unmanned Aerial Systems (UAS) interference
« Reply #5 on: June 19, 2014, 09:22:52 AM »
how do we now that this loss of signal is caused by interference? usually when bumps make broken things suddenly work, it's a loose connection

we don't... hence I mentioned that my post was an opinion
 ;D

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