When T60 running, FM reception on nearby radio is noisy

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Muse · #1 Post by **Muse** » Thu Aug 30, 2007 1:34 pm

I have my T60 on the kitchen table, powered by AC adapter. When the laptop is on (not suspended), the mini-stereo system has noisy FM reception. Why would this be? It happens whether or not I have my 2.4 GHz USB connecgted Logitech mouse installed. The stereo's FM antenna is a dipole, mounted on a rabbit ears on the refrigerator. My Internet connection is by way of a Buffalo wireless router in an upstairs room. What is at play here? Thanks for any help.

Troels · #2 Post by **Troels** » Thu Aug 30, 2007 4:26 pm

It's an RFI problem, due to bad shielding. You will find this wide spectrum of noise with any laptop, regardless of brand - but indeed, the problem has escalated with faster bus, processors and more compact design.

When i put a portable radio ontop of my T60p while it's on, there's only white noise on the radio. As soon as i set the T60p to suspend the intererence stop.

I don't think it's possible to make a better shielding than now, even desktop ATX cases have some new requirements with steel drive bays and PCI brackets not to be removed when no device is installed.

Muse · #3 Post by **Muse** » Thu Aug 30, 2007 4:58 pm

Thanks. I wonder if a workaround is to hook a rooftop antenna into the mini-stereo.

Troels · #4 Post by **Troels** » Thu Aug 30, 2007 5:24 pm

Surely that would solve it, if you can if you have access to the roof and all. Remember to use the correct wave impedance cable going to the stereo (usually 75 Ohm).

The RFI from the notebook isn't that strong, so on there roof there will be no interference.

Muse · #5 Post by **Muse** » Thu Aug 30, 2007 6:42 pm

Thanks. That's what I'm going to do!

#6 Post by **GomJabbar** » Thu Aug 30, 2007 7:06 pm

If you have Cingular, or one of the other WWAN options, and if it is operating at the 850 Mhz frequency band, that can cause noise on audio systems. I have seen this happen on my own setup using a Sierra Wireless 860 Aircard. One set of powered external speakers I have make a disagreeable noise when my connection is operating at 850 Mhz. The other set of powered external speakers is unaffected. When my connection is operating at 1900 Mhz, I do not hear any noise from either set of speakers. I have read of others with similar experiences on the at&t/Cingular forum.

acasto · #7 Post by **acasto** » Thu Aug 30, 2007 7:39 pm

You can hear the extent of some of the interference with a cable tracing probe. I was using my Fluke a few weeks ago to listen to things around the house. The electrostatic air filter is the worst, it sounds something like a light saber. LCD screens seem to give a very high pitched tone. You can eveh hear the pulse in a remote control when you push the buttons.

#8 Post by **bill bolton** » Thu Aug 30, 2007 9:54 pm

Troels wrote:It's an RFI problem, due to bad shielding.

It's an RFI problem but almost certainly due to low primary signal strength. Rabbit ears on the refrigerator will not be providing a solid primary signal to the FM receiver, which is probably running with its AGC way up!

Cheers,

Bill B.

When T60 running, FM reception on nearby radio is noisy

When T60 running, FM reception on nearby radio is noisy

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