Thread: Wireless audio interference from Scarlet-W - problem and solution

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  1. #1 Wireless audio interference from Scarlet-W - problem and solution 
    Junior Member Michal Larsson's Avatar
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    Hi all,

    Thought I'd share some problems I've had and what seems to have caused it.
    Basically the issue was sweeping interference (sounds) that could be heard through audio monitoring when using wireless audio (EW100 series G3 - Sennheiser).
    This could happen at random and did not seem to be coherent in relation to areas with much or little possibility for radio interference from other devices or general radio communication.

    The equipment in question was a Scarlet-W with the base I/O, a Blueshape Granite v-lock battery, a Videodevices 7" monitor with PIX-LR audio unit, connected via SDI from base I/O to SDI1 on monitor. The monitor ran on its own battery from a Sony battery. Wireless was enabled in the camera.

    When the transceiver unit (a Sennheiser EW100 G3) was disabled we could clearly see significant RF level (which normally shouldn't show any indication). This suggested that something within the space was emitting significant RF that was picked up by the receivers. We also tested this with the stationary EW300 G3 units, all within incremental distances of 0,5, 1 and 2 meters from the camera. We tested with very different receiving frequencies. To verify we also brought out a AKG stationary receiver unit which also showed RF.

    I then moved on to see if there could be anything in the camera that could cause this, so I turned camera on and off. At the very same instant camera was turned off the RF disappeared and was visible again when turned on. We then turned off wifi, which was not affecting RF. I modified the fan settings, this didn't result in anything either. What about cables or any other connected signals. I turned off SDI signal from the base I/O and voila! Enabling/disabling SDI signal caused the spike in the RF and it only happened when a cable was connected. 75 ohm standard HD-SDI capable cable at 50cm length. We then swapped out this cable for another type and length and the RF was not there anymore. Swapped back to the 50cm cable and RF spikes on all units again.

    We are still checking what type of cable does effectively cause the SDI cable to become a pretty strong RF antenna that interferes with the wireless packs at a multitude of frequencies.

    I'm certain that someone else has had this experience, if so, please share your findings as we are trying to understand the problem better.

    Thanks!

    Michael Tebinka
    Director of Photography / Freelance Colourist


    Scarlet-W #2386
    Portfolio: ohsoweird.com
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  2. #2 Possible source: SDI cables 
    On many shoots, a badly soldered (or broken solder connection) to the shield on the BNC cables going from camera to accessories causes RF spray that spoils audio, both in camera and on the wireless receivers at the sound recorder. Try testing with all new BNC cables in your build.
    It is also possible for the BNC connectors on the monitor and the I/O module to have damage that will cause this RF spray.
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  3. #3  
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    Hi Michal,

    Could also be a dodgy 3.5mm jack to xlr cable, had the same issue on a shoot last week. Soon as I replaced it, it was fine.

    Could be a multitude of things though TBH.

    Test cables, try a different channel on the G3's / test as many things as you can to pin down the RF interference issue. I even had the wireless of a Small HD monitor cause issues before on a recent shoot create problems which as soon as I turned to flightsafe mode fix the issue.

    Test test test as much as you can to identify the issue.

    Skol!

    Craig Lees
    UK
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  4. #4  
    Junior Member Michal Larsson's Avatar
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    Hi Christopher,

    Yes it was indeed the SDI-cable that was faulty. We are yet to dissect it but trying out other cables removed the problem completely. Just ordered some high quality spares to avoid this problem in the future. You always learn something new :)

    Michael Tebinka
    Director of Photography / Freelance Colourist


    Scarlet-W #2386
    Portfolio: ohsoweird.com
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  5. #5  
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    Ouch! Well glad to know this as something else to mentally file away if I need to troubleshoot an issue in the future. Consider if the camera department's SDI cables are dodgy!
    http://IronFilm.co.nz/Sound/ (Sound Recordist based in Auckland, NZ. Happy to travel too)
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  6. #6  
    Junior Member Michal Larsson's Avatar
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    Quote Originally Posted by David Peterson View Post
    Ouch! Well glad to know this as something else to mentally file away if I need to troubleshoot an issue in the future. Consider if the camera department's SDI cables are dodgy!
    Indeed! You will notice the issue if you are getting RF signal but no transceiver emitting (transceiver/s OFF) + increased RF signal the closer you get to the camera/cable. :)

    Michael Tebinka
    Director of Photography / Freelance Colourist


    Scarlet-W #2386
    Portfolio: ohsoweird.com
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