mrel - The only mod that I know of is to restore 800 Mhz coverage on models made before 1995.
This was done back a few years ago when cell phones still used the analog mode - useless now.
What was done was to simply take a pair of side-cutters and cut one leg of the diode labeled: D13.
The instructions were like this: Remove Batteries, Antenna and knobs. Remove the 4 body screws.
Unsolder BNC connector, unscrew 4" Hex/Nuts posts holding upper board. Unplug upper board.
Remove 3 sheilded screws and lift the shield. CLIP DIODE D13. Reassemble the radio and test
)
I wouldn't actaully do this- but you asked about mods to the RS Pro-37 - this is the only one I knew of.
You should start lQQking for a new scanner - do some research and enjoy a new/modern scanner !!!