TH45AT.5
 Tune the radio DOWNWARDS in frequency until the PLL
unlocks.  Note that the radio will beep when this happens, and the
waveform on TP1 will change.  Tune the radio about 1 MHz higher so that
the PLL locks up again, and note the voltage on the testpoint, TP1.
Now, tune the radio to the LOWEST frequency that you want to be able to
receive.  Adjust TC1 until the voltage on the test point TP1 is the same
as what was noted earlier.  Button the radio back up, and you're
done.  You will not be able to tune the PLL to any range you want.
There are limits.  On my radio, I have been able to retune the radio so
that I can recieve from 439.2-468.6 MHz with a set of batteries fresh
out of the charger.  The tuning range will probably diminish as the
battery voltage decreases.  I have not retuned the PLL on my 2m HT, but
I'd imagine the same technique will prove fruitful.

I may have some more information on these radios someplace.  If I can
find it, I will add to this posting, and post it again with the updated
information.  Enjoy. Kenneth J. Hendrickson    N8DGN
Note: I haven't tried or verified these mods, proceed at your own risk!
WA2ISE