Before I forget:
It looks like the power is the problem, but just to add more evidence on the pile : I always get astonishingly poor reception from one of those smartphone-FM music player devices.
This site notes the trouble but no details...?:
924/944/968 Stereo FAQ
"When installing an aftermarket radio on a car with an active antenna system, it seems to be a common problem to forget to apply power to the preamplifier. The following are the most common symptoms:
Poor reception on FM - only a few strong stations will appear.
Virtually no reception on AM.
Note that the preamp must be connected to a switched source to avoid running the battery down. Again, this is the 'power antenna' lead in the radio's wiring harness."