That's true. However, according to the driver documentation, the transmitter chip is capable of measuring received noise level. Couldn't that be used to find an appropriate frequency? Additionally, the transmitter seems to support RDS, so maybe an alternative frequency table could be used to automatically switch the frequency on both the N900 and the radio receiver.

You should start fmboost AFTER starting fm transmitter. If you plug or unplug cables, start or stop fm transmitter, the boost is undone.

shadowjk, fmboost is now integrated in Simple fmtx desktop widget, you must only configure the widget to use it.

I thought I'd dig this one out because I'm about to take a motorway/freeway trip tomorrow and have to take the car which doesn't have an aux input on the radio, so that means using the N900 FM transmitter. Being a long trip, this will invariably mean changing frequencies on both the N900 and radio from time to time to keep the frequency clear. This wouldn't be so bad if I could convince the wife to drive, but it'll be me driving as usual, so I won't be able to keep fiddling with the frequencies without pulling over every dozen miles or so.

The original poster was onto a good thing with this and it was working out, but the thread kind of fizzled out when discussing using fmboost.

There is still a good case for developing a program to scan for clear frequencies. This could either be used to build a map of clear frequencies on specific frequently travelled routes (motorway networks perhaps), or as was suggested, perhaps to use RDS to enable the FM transmitter to renegotiate the 'station frequency' on the fly. I presume that the N900 is not capable of transmitting and receiving simultaneously, anyone know this?

Changes of designated frequency could be triggered by GPS location if a community created 'clear frequency map' was developed from the pooled N900 users frequency scans. The resultant frequency map might be used as the basis for the development of similar applications on other platforms, a bit like those dynamic speed camera databases.

It's all too complicated for me to even contemplate, but it would be dead neat if it could be made to work.

Here is something everyone can do to get trouble free transmission from your N900 to car radio.

Either unscrew the whip or push down the antenna (depending on the type of radio antenna fitted) or try the following...
what is needed is a simple switch to disconnect the antenna wire from your radio, the centre wire in the coax of your antenna lead going to the actual antenna on your car, what this will in fact do is stop the antenna from working and will give you a quiet radio that will pick up the local transmission from your N900 as it will be in the car without any interference from an outside broadcast.

Worth a try.

rather sound idea! cut the coax somewhere accessible (under steering wheel most likely) and install male / female adaptors to the cut ends, the ones for old tv aerials would work just fine, 99p at B&Q, and if you really want to make sure run an alternate connection to beside your cubby-hole or wherever you keep your n900 while driving.

personally i get a fantastic signal all the time on 1 frequency, keeping my n900 in the cubby-hole directly below my stereo.

Yep good idea that as all you need to do is null the signal from the antenna stop it from getting to the radio.
Incidently you can buy an antenna switch, switch out the external antenna is all thats needed.

The fm transmitter chip actually has the capability to scan for least noisy channels and transmit there.. I don't think the kernel driver supports it though. I don't know if it can send and scan at same time.