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Measurement of RFI

Discussion in 'General Discussion' started by PhantomRock, Jun 11, 2014.

  1. PhantomRock

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    I flew in a difficult environment today (gas line cut, difficult terrain and perpendicular to power line cut).
    I was wondering if anyone has done any in-flight RFI detection and measurement.

    This would be something similar to:
    http://www.winradio.com/home/erd.htm
    for wifi and control frequencies.

    Audio output would be picked up by the Go Pro camera, so you can get out of that location before you get into trouble.
     
  2. Dalite

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    Location:
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    The WinRadio sniffer would almost reach the GPS spectrum, and could not measure noise in the WiFi or 2.4 GHz controller range.

    Chances are that the GoPro will be generating more electrical noise than the environment you are flying through.

    If the GoPro was turned off, the sniffer may be able to detect RF interference, within it's frequency range, from the area you are flying in.
     
  3. PhantomRock

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    Thanks for the response.

    I guess I was not clear, yes i saw the frequency response of this unit.

    What I meant is that I am looking for a device "similar" to this one only in operation, meaning it should have the following features:


    1. work in 2.4 and 5.8GHz bands
    2. emit an audible escalating tone, or output that I can feed to a transmitter etc.

    I only used GoPro as an example to keep the post simple.
    I would feed this to a transmitter or strobe or other way of notifying me.


    I landed quickly when I ran into interference, some sluggishness and delay in control response.

    In the future, I will be having a $15-20k camera on a larger platform, and want a more reliable way.
    Upon reflection, I realized this must be ground based and cannot be in-flight, as there is no way of filtering out the Phantom's use of these frequencies.
     
  4. Dalite

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    I don't think I can be much good, other than recommending a call to Optoelectronics and see if they can tailor a solution for you. They specialize in portable near-field receivers with fairly wide range and various storage, audible and signaling options.

    A good Doppler direction finder setup with handheld beam or log periodic antenna could be used to sweep an area prior to flight, but then there is always the chance for interference arising after the flight begins.

    There are a number of cheap software defined receivers available, but they are gernerally not sensitive enough in the SHF bands to do much good and would require additional support hardware.

    Probably the best hope would be incorporating the most efficient shielding possible on all circuits that provide input lines to the flight controller. The solution is to try to make the signal carrying circuits as bulletproof as possible without adding more weight than the craft can lift and maneuver with. On the Phantoms, that could be as simple as twisting the compass lead going to the GPS board, twisting the GPS cable from the board to the NAZA - cost free attempts to improve data integrity on all input signals to the flight controller.

    From there, ferrite beads, shielded cables - effectively a design rebuild using more thoughtful RF design techniques. By the time you approach the type of data integrity that the camera expense warrants, you have pretty much developed a new platform.

    Probably not much help in anything here; just some thoughs.....
     
  5. PhantomRock

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    Thanks, this reminds me of the Ham Radio foxhunts I had as a kid, oh my is it really 40 years already?

    We used to use an AM receiver tuned to an unused station for rough sniffing of noise. I had a bloomberg radio (probably still have it) that I got for free at a show, it just had the Bloomberg station and an large adjusting pot, so it was easy to use it for finding all kinds of noise, but that was in the lower frequencies....

    Back to the topic, I later found a microwave dish at the gas substation below. Anyhow it was a really tough environment.
    The barometer must have gone crazy as you constantly had large drops. I intentionally took it there to test it, and just got a little more than I bargained for...

    Thanks again.