R7000.22
Part 2/2

                     Changes for BS-8 Module

     I haven't tried the BS-8 module, but encourage  you  to
     try  using it as is, without modification unless neces-
     sary.

     These steps are needed only if you cannot find settings
     of  the  side  mounted  aligment  controls that get the
     display to behave as specified in the owner's manual:

       1.  Remove C233, the 33 pf disc capacitor,  from  the
           printed circuit board.

       2.  Replace coil L204, the 4.7  microhenry  inductor,
           with a 6 or 7 microhenry inductor.


                            Alignment

     Follow the alignment procedure in  the  SM-220  owner's
     manual  to  adjust  the  panadaptor.   This consists of
     adjusting 2  potentiometers  and  1  trimmer  capacitor
     through  holes thoughtfully provided in the side of the
     cabinet.

     The alignment instructions  rely  on  the  use  of  the
     internal  Marker  Generator to generate a signal at the
     center of the passband.  If you haven't  converted  the
     Marker Generator circuit, you can tune your receiver to
     a frequency with a signal present at a known  frequency
     (like  162.550 MHz - the National Weather Service), and
     use that as a frequency standard.

     Most of the time spent in aligment will be in alternate
     adjustments  between the trimmer capacitor and the wide
     band sweep  potentiometer,  which  interact  with  each
     other.


                         Wider Bandwidth

     The SCAN WIDTH switch on the stock SM-220 can be set to
     display a 40 KHz or a 200 KHz wide picture.  I adjusted
     my modified SM-220 to display a 100 KHz or  a  500  KHz
     wide picture.  By adjusting the controls on the side of
     the SM-220, wider bandwidths are  possible,  but  wider
     bandwidths make it more difficult to resolve individual
     signals close to  each  other  in  frequency.   As  the
     bandwidth   gets  wider,  the  horizontal  sweep  loses
     linearity, causing the graticule calibration  lines  to
     be inaccurate.

CONTINUED IN R7000.23