It is not noise so much as it is an actual reduction of transmit power when anything USB is plugged in. >> Check it out <<

Transmit power OEM is at about 114 on a scale from 0 to 120. When the charger or USB cable is plugged in it drops to as low as 88. Hence the noise that is always there becomes more prevalent (signal to noise ratio and what have you).

To Boost the transmit power to 118 (120 seems to degrade in quality after about an hours use) use the FM-Boost app that can now be found in extras >> HERE <<

That thread I first linked to above is where the FM-Boost applet was actually developed using input from various members from around the world.

(Shhhh! Don't tell anyone but this forum actually does get things done when the nay sayers, ne'er do wells, malcontents, and run of the mill anus weasels are kept at bay. )

Regard, even when FM-Boost and Media player are already activated plugging in a USB cable will still cause a drop in power. Simply reactivate FM-Boost after plugging in or changing the FM frequency and you will be rockin' once again @ full tilt boogie (118).

For more advanced users you can follow along as a more pervasive method is being developed by qwerty12 in >> THIS << thread.

But please leave any anus weasles at the door when you come in.

I get the same thing. If I try to use the FM while charging it pops up a yellow message in the middle of the screen that says

Unable to use FM transmitter while USB is connected.
Unplug USB to continue using the FM transmitter.

Are you using a Nokia OEM charger or a generic one?

So far only tried it with the USB cable connected to my computer, have not tested it yet with a wall charger.

I too get the same error with 1A car charger bought from ebay. Why is n900 thinking a usb is connected when it is infact the charger. any way to make it think that there is no usb connected?

i have the nokia dc10 charger and have no problems using fm transmitter while charging pr1.2. i did have the nokia dc6 charger on pr1.1 and again had to problems. both were oem.
mark.

when i connect the charger and then start fm it gives error that that usb is connected. however when i have fm trans running then plugin in the charger it does not give an error. may be something wrong is going on when charger is connected and then the fm trans is switched on.

can you confirm?

in case you experience the issue, confirm in this bug. https://bugs.maemo.org/show_bug.cgi?id=6792

Thanks guys for the replies. Just recently, it started working again. So now the FM transmitter works while charging using the wall and the car chargers. I have no idea how it happened, but it just started working like before. The PC usb cable still doesn't allow to use the FM transmitter though, but that's ok.

mehulrajput, as I said, for me the transmitter doesn't work just with the PC usb cable, and when I try to do what you said ( fm trans running then plugin in the charger), it gives me a message saying that I should unplug the usb to use the transmitter. So I don't experience your bug.

From a very vague memory I have, some chargers don't work (non-OEM) because there is a chance the poor build quality will result in the charger acting as an antenna to boost the power of the FM transmitter to levels that are considered illegal in some countries... (re: requiring a broadcast license)

For the record, FM-boost worked wonders for me, I highly recommend it for anyone experiencing quality issues with the FM transmitter.

I was able to use a third party car charger while playing FLACs with a level of clarity unexpected for an FM transmitter.

I'm all for boosting the power levels, illegal or not - I can assure you that my mp3 collection is better than almost all the crap they play over the radio anyway, as far as I'm concerned broadcasting it would be a public service! ;-)