"If you want to use a scanner at bases etc you need one that covers civilian and military airband which is something like 108-137mhz (civil) and 200-400mhz (military).
Now I'm no expert, and am guestimating the above frequency ranges, but they are something like.
The scanner you have GRE PSR-255 doesnt cover these frequencies I'm afriad. Although it says it covers 26-512mhz there are 'gaps' in its coverage, in fact it only covers:
"Frequency Range - 26-54Mhz 66-88Mhz,137-174Mhz, 380-512Mhz"
As you can see it doesnt cover between 88Mhz - 137Mhz which is where the broadcast FM range (radio stations) and civil airband sit. There is then a gap between 175Mhz and 380Mhz which is where the military airband sits.
Sorry for the bad news! Like I said I'm no expert at scanning by a long chalk but it looks like you fell into a similar trap I did when loking at scanners - they will often say in big letters on the box 26-512Mhz but its not till you look at the actual specs that you see the gaps in coverage which are more often than not right where you want to be listening!!
The other unfortunate is that in order to get a handheld scanner that covers both civil and military airband you tend to have to pay a premium for a reciever that doesnt have any gaps in its coverage - even though (if you're like me!) you're not likely to use it to listen to anything else!!
Kind Regards
Neil
