I got to thinking about the frequency in discussion.  Then I subtracted
21.4 Mhz from it, and came up with a frequency in the aircraft band...
Which makes me suspect that what happened is that the actual
transmission was in the aircraft band, and the 150 Mhz band signal was
in fact an image frequency signal instead.  Check the IF frequency of
your radio in the manufacturer's specs, and listen 2X the IF both above
and below the desired frequency.  If you are listening to a
particularly strong signal, you should hear an image both above and
below the real frequency.  Believe me, it works!  The image signal above
the real frequency is stronger by far than the image signal below the
real frequency.  
--- Platinum Xpress/Win/Wildcat5! v2.0
---------------