GSM interference in speakers - Page 1
Forum section: electronics / projects

author: hlavac
author_rank: Frequent Contributor
timestamp: June 15, 2012, 11:20:01 am
content: I have a really old but excellent set of active speakers.They have only one problem - they pick up a lot of interference from my mobile phone.What can be done about it? Should I put some small capactor across the input to short out the 800/900MHz RF signal or something?

author: Psi
author_rank: Super Contributor
timestamp: June 15, 2012, 11:31:40 am
content: You could also try lining inside the speaker box with metal foil and connecting it to ground.Just be sure that the foil cant short anything out

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: June 15, 2012, 11:43:04 am
content: Or maybe move here:http://en.wikipedia.org/wiki/United_States_National_Radio_Quiet_Zone

author: hlavac
author_rank: Frequent Contributor
timestamp: June 15, 2012, 11:50:27 am
content: Yea or thow away the phone thats good too

author: G7PSK
author_rank: Super Contributor
timestamp: June 15, 2012, 09:47:28 pm
content: My phone does the same with my computers speakers, i can tell that I have an incoming call before the phone rings due to the chatter on the speakers caused by the phone that comes in a second or so before the ring starts, not much that I can practically do about it in reality.

author: T4P
author_rank: Super Contributor
timestamp: June 16, 2012, 05:17:02 am
content: Oh wait, i now know why i am not getting any interference i forgot i am using a 3G phone

author: IanB
author_rank: Super Contributor
timestamp: June 16, 2012, 06:07:49 am
content: Quote from: hlavac on June 15, 2012, 11:20:01 amGSM phones are very effective system disrupters--they inject that annoying chirping noise into absolutely all audio devices, and non-audio devices too. That's why the authorities don't like phones near medical equipment in hospitals. Your speakers are not at fault, since your phone will do the same thing to any speakers or anything else within range.Two solutions are either to move the phone further away from the speakers, or to use a 3G phone since 3G doesn't generate the same interference that GSM does.

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 16, 2012, 07:32:54 pm
content: Try a new phone. The newer ones are designed to avoid that problem to the extent that it's difficult to reproduce the problem on purpose.

author: IanB
author_rank: Super Contributor
timestamp: June 16, 2012, 08:12:09 pm
content: Possible solution here:http://www.maclife.com/article/iphone_buzz_kill

author: Unknown
author_rank: Unknown
timestamp: June 17, 2012, 12:44:15 am
content: Quote from: NiHaoMike on June 16, 2012, 07:32:54 pmMay or may not work. While 3G and 4G phones will interfere a lot less than GSM they will all fall back to GSM reception in many locations unless specifically told not to. Placing phone away from speakers is the cheapest and most proven fix. Works a treat with early Fluke 87V meters too.

author: teholabs
author_rank: Contributor
timestamp: June 17, 2012, 03:54:08 pm
content: Quote from: hlavac on June 15, 2012, 11:20:01 amIt isn't a 800 MHz you can't hear that high... Regular old GSM is time division multiplexed which means the transceiver turns on and off on a ms time scale putting its data in windows. This makes harmonics in the KHz range, which is what you hear. Typically in these systems you hear it because of a single ended amplifier stage. If you can hear it without your speakers plugged into anything then it is likely coupling magnetically to the voice coil. Remember the LSB for a 1 volt 16 bit system is only 15 uV, consumer audio tends to be less than a volt meaning it is even more easy to pick up some noise. If it is a single ended system amplifying the switching harmonic then you could put it in a metal box well grounded and lined with iron or some other magnetic material. That's as good as you are going to do without using superconductors.