-
OT: engineering fun – rf noise on fibre cable
Here’s an engineering quandry:
we have a DVI monitor that is popping green bars and losing sync briefly whenever a cell phone on AT&T EDGE network is nearby and receiving data (like a text). It also seems to be affected by the construction crew next door and whenever they start drilling.
I’ve swapped the monitor, problem remains. The only thing that may be culprit: we have a 50meter Avenview fiber optic DVI cable running to the machine room. It’s fiber, so RFI is not an issue, but at the end is a rather large metal hood that contains the optic->DVI converter. Could it be introducing that much RFI noise that the signal is getting garbled?
Any ideas how to shield or troubleshoot?
-
7 Replies
-
AT&T phones cause us constant pain in our audio room. They need to be turned off, not just silenced. In our case it’s getting in through the condenser mics. When this first started happening I thought the mics were starting to go south. The unfortunate part is proper grounding doesn’t seem to prevent this interference. We’re using star-point grounding and still have this problem.
John
MacPro 8-core 2.8GHz 8 GB RAM OS 10.5.5 QT7.5.5 Kona 3 Dual Cinema 23 ATI Radeon HD 3870
ATTO ExpressSAS R380 RAID Adapter, PDE Enclosure with 8-drive 6TB RAID 5
24″ TV-Logic Monitor
Final Cut Studio 2 (up to date)Pro Tools HD w SYNC IO, Yamaha DM1000, Millennia Media HV-3C, Neumann U87, Schoeps Mk41 mics, Genelec Monitors, PrimaLT ISDN
-
Same problem on my room. It gets into the audio amps at the desk.
Tom -
Same here with analog audio: pops and crackles and hisses when an EDGE phone is being used.
My quandary is this “digital” connection. Fiber Optic to DVI…. I just assumed it would be less sensitive to RFI.
-
Try disconnecting your input to the DVI>Optical converter and then to the Optical>DVI converter in turn to try to isolate where the interference is actually getting into your system. The monitor may just mute and show nothing but it’s worth a try. Not too many places it can get in. Do the monitors nave internal power supplies or “wall warts”?
Tom -
You guys must be imagining these things: the FCC sticker says those phones have been RIGOROUSLY tested and guaranteed not to interfere….right?
……right?
🙂
Have you tried making some kind of Faraday cage around the A/D converter? My guess is circuit board traces on the actual boards are acting as antennae.
-
Sure…
Tell that to everyone who uses wireless mics….
_______________________________
Wayne Carey
Schazam Productions
https://web.mac.com/schazamproductions
schazamproductions@mac.com -
Farraday cage. Sweet. That’s what I’ll give a go….
What’s puzzling me is that this should be a totally digital path DVI converts to fiber optic converts back to DVI. There REALLY must be some interference if it’s causing hiccups in the conversion.
Reply to this Discussion! Login or Sign Up