There are two options to choose from.
No. 1. Whether you get used to it and don;t pay attention anymore, just increasing time compressing again or:
No.2. You'll use this , mod
http://www.subsim.com/radioroom/showthread.php?t=174225
and make sure you're enable this feature:
15. WarNews - by Stiebler and h.sie
TC doesn't drop down to 1 when a radio message is received.
OR
SH3 Commanders feature:
SH3 Options/ Time Compression/ When receive Radio Report - You can set MAX TC to whatever you like.