I bought a belkin tunecast 3 a couple of months ago, and just recently I tried out stereo tool's fm transmitting function on it. After a couple of weeks of tweaking, I came up with this preset. For those who have a belkin tunecast 3, try it out!
And for those who don't and want to try it, you can find one for 10-20 euros on ebay... 
Few points of notice
For this preset, you should switch your broadcaster to mono mode, which you can do by holding the upper left button. Otherwise there will be no stereo, and rds reception will be bad.
The sound volume of your sound card could be different from mine. If it's higher, you could notice lots of distortion, if it's lower, maybe the stereo will be gone or there will be alot of noise on the background. You can fix this by clicking on "configure sound cards", and then tweaking the output volume.
This is a standalone preset, not sure if it will work the same with the vst / dsp plugins.
Anyway happy listening... For background information i refer to this topic.
Download preset