One other comment, I had severe rf in my audio problems when I got my 590, 
that radio seems more suceptable than most.  I had to put in a couple of 
those line isolaters and that solved the problem, I can dig up the link if 
anyone wants it.  There were some other fixes with those microphones, 
running a wire down the center of the cord from base of microphone to 
ground on the radio as I recall.  That might have b een the 50, but those 
microphones have been known to have r f i problems as well.  As mentioned 
above, I went from a 2000 with no r f i at all to the 590 and had severe 
r f i which the coax isolators fixed.
73
Butch
WA0VJR
Node 3148
Wallace, ks.