Could to much gain , cut scanner sensitivity ?

[BITT211]

hello ! , I have a yagi antenna , paired up with a gre psr 400 , lmr 240 , 20 ft feed to scanner , yagi power spec's ,
freq. range - 430-450 mhz
gain [forward] 8.04 dbi
front to back - 24.12 db
I am hitting tower 12 miles away
only scanning uhf freq's
whats happening , sometime alert tones are heard / other times not , most of time voice transmissions clear ,
Question is { *** could this antenna be to strong for this radio ***] over powering scanner . yes tried ATT position.

 

[ka3aaa]

you are good with that antenna and only a pre amp or very close extremly powerful signal could overload the scanners front end.