copied from the Internet:
From: stoll@ocf.berkeley.edu (Cliff Stoll)
Newsgroups: rec.radio.amateur.misc
Subject: Wideband Modification for Icom IC W21AT Dual Band HT

The Icom IC W21AT handi-talkie normally receives two bands:
136 to 174 MHz and 440 to 450 MHz.

You can program it to receive
50 to 300 MHz and 300 to 999 MHz.

To do this, turn it off, then simultaneously hold down
the # and the B keys while turning it on.  Keep them pressed
for 2 seconds after turning the rig on.  

The LCD display will go through a self test, and you'll
then have a wideband receiver.  It's not very sensitive
far from the ham bands, but it's handy for listening to
6 Meters or as a portable scanner.

Note that this modification does not require any cutting of 
diodes or rewiring -- it's entirely front panel.

Cheers es 73's,
Cliff Stoll  K7TA
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Note: I haven't tried or verified this, proceed at your own risk. WA2ISE
"A thousand a week doesn't go far anymore" - George Jetson