You need a better filter such as ceramic, as FA filter does not effectively filter out frequencies so close to 1090 Mhz (such as 920 or 960 Mhz). It does however remove effectively the GSM850 (850 Mhz) Cell frequencies.
Please see this post which has graphs. The graphs “image 3 of 5” and “image 5 of 5” show this very clearly.
Also, scrolling up/down and reading other posts in this thread may be helpful.