I have just been a test drive with active antennas which made a major improvement compared to originals, I placed the antennas front and rear window which was better than rear side windows. but still hiccups between houses and roads where is noise barriers on both sides of the road. ProgDVB shows the signal strength stays in 100% all the time, the signal quality varies between 40% and 100%. Of course, this can't be compared between different countries but this is here in Finland. I still want to try car DVB-T tuner if I may borrow one from somewhere, so I can see what is difference between usb tuner and car tuner.
For comparison, with original antennas signal was between 60% and 90%. Signal quality was between 0% and 100%.
TV signal is difficult to catch, so perfect reception is quite hard to get when moving.