Nice logo
The 'fix' should, surely, be that messages are removed from the log after a reasonable time - allowing the log size to remain small enough not to affect the game as badly as it does in 'stock', without altering what you get by way of distance.
Having said that, this is a curious understanding of 'realism' - in reality your radio guy would bring you the messages addressed to your boat, and wouldn't copy a message that wasn't addressed to you. (Some listening in on messages of interest doubtless occurred) - he'd also only listen in on relevant frequencies - no radio op ever listened to every message on all nets, there'd be nets for sub ops and I'd be amazed to find they weren't further divided between commands - ie I'd be surprised to find Asiatic fleet boats listening out on the same radio freqs as the boats out of Pearl.
Cutting the range of contacts to retain only those relevant to you (by range) is therefore no more 'gamey' than any other work round... it's simpyl reducing the level of radio traffic to that which is relevant, which is what would have happened in reality. (Just in a different way).