Is it really possible to use a scanner without being exposed? I heard
from few sources that scanners produce internal oscillator signals
that can be detected.

aqnd my question is, does this screw up Smartsignmedia and Mobiltrak to
detetrmine which radio station you're listening to?

They're using machines to read the local osciallator on your car radio and
looking 10.7 MHZ away to determine which radio station you're listening to.

But they're looking for which radio station between 88 and 108 mhz you're
listening to, so advertisers can target their advertising to you on freeway
signs.

But if you're listening to a scanner in your car instead of the car's radio,
and if their machines can handle it, they'l get a frequency readout such as
"144. 250 mhz" or "455.325 mhz", in which case they'll probably be scratching
their heads and going "huh?"

Since this would be an accurate readout of which station or frequency you're
listening to, it doesn't really screw them up. It just confuses the heck out of
them.

However, my own scanner uses a local oscillater of 240.1 mhz, which I imagine
probably would screw them up since their machines are looking for and reading
as 10.7 mhz away from the local osciallator frequency.

They would probably get a completely wrong readout of what station I'm
listening to.

Of course, this also has it's possible drawbacks