the signal strength on my pca tuner is usually very accurate. Full strength on the bars corresponds with a strong signal, no aerial or not tuning to anything leaves me with no bars on the display.

As for the bass/treble attenuation, that's a function of the player, it attenuates the bass and treble according to signal strength, I think you can disable it with a config.ini setting something like fm_bassboost or something like that (anyone?)