copied from the Internet netnews:
Newsgroups: rec.radio.amateur.misc
From: dplumb@cix.compulink.co.uk (Dave Plumb)

the mod for the C528
it's: 
 
   VHF F+0 F+D UHF F+L F+0 F+B F+L F+3 A 
 
The "L" is the light, F+L means press function, and while pressing function, 
press the "Light" button.  The above sequence opens 
up the set for rx for all limits. 
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Note: I havent tried or verified this, proceed at your own risk.  WA2ISE