I've forgot to add AM is sadly out of the picture. There are no audio AM broadcasting left in France, we still receive BBC very well but not for long. So this is 100% an FM matter. Most use the AM amp signal as a way to wire a bluetooth receiver anyway.
I've added the schematics of the front-end. Once again I suck at reading schematics. It's built around a TDA1575T from Philips which is a front end chip housing the LO, Mixer and IF Amp. I think BF999 would be the RF amp? The alignment instructions say to tune L6 which would be the local oscillator I think, L2&L4 which would be bandpass filter?, and F1 which would be the IF filter before the amplifier, and after that the rest of the IF alignment.
Let me know if I got everything right or not, it's always a great exercise.
I'll do the antenna measurements mounted on cars yes. It's also useful as in averaging the antenna because of production variation, but also because being 30 years old I except some to have aged quite a lot compared to new in terms of characteristics. Regarding external signals, how can I avoid nearby stations from interfering with the VNA reading?
