I've got an early "Modified by Frank Van Alstine" FM-5 (pre-Super Tuner, etc.). Appears to have original boards with components, esp. capacitors, added. Trouble with it and my previous Heathkit AJ-14 is annoying sizzling sound heard in the background when listening to the (now) only classical station in our market (the sound of microwave links?). This has been a problem for years.
About a year ago, I modified an FM-1 (with FM-3 multiplex board) using FM-3 Zone's parts. Nearly electrocuted myself in the process

, but surprise, no sizzle! I could listen to the thing for hours on end, when I had the hours.
Last summer I got the little Sony. No sizzle here either. Plus, I could listen to classical on HD2 instead of Garrison Keillor on Saturdays (sorry Keillor fans). Plus smooth jazz is available again in our market on HD2. I can hear increased high end when the unit switches from analog to digital. But can't pick up the Easy Listening station about 75 miles south of here, though it comes in on the car radio. Maybe a roof antenna would help.
What I want to know is, is my old FM-5 upgradeable as the Super Tuners are, and, if so, would I still be saddled with the sizzle?
