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lbfb - control the lband filter bank

SYNTAX:
    lbfb {} {filter filter filter..}

ARGS: 
    noarg     list the filter numbers and their frequency ranges.
    filter    filter number 1-9 to include

DESCRIPTION:
    Select the filters to use in the lband filter bank (between the 
    dewar and the post amps). Enter 1 or more filter numbers to use.
    The same filter will be used for polarization A and polarization B.
    If more than one filter is requested, then the signals from 
    each filter will be or'ed together. 
    Entering lbfb without any arguments will list the filter numbers and
    their frequency ranges.

EXAMPLES:

lbfb   5        use filter 5 (1100-1800 mhz).
lbfb   2 3      use filter 2 (1120-1220) and filter 3 (1230-1470)
lbfb
filter   freq
  1    1370 hipass (ext Output unit. Use with filter 5)
  2    1120-1220
  3    1230-1470
  4    1550-1820 
  5    1120-1800 
  6    1360-1470
  7    1320 hipass 
  8    1180-1280
  9    1280 hipass (ext Input unit. Use with filter 5)
WARNING : Don't overlap in frequency any of the filters  2 thru 8.
       They are or'd together and will cause ripples in the
       bandpass.
       Filters 1 and 9 are external and will not cause overlap ripples.
       They need one of the filters 2 thru 8 installed (normally 5) so 
       the signal will pass thru the switch box.
NOTE:
    An 1120 to 1760 bandpass filter is normally in place in front of the
    filter bank (unless barbara's switch is used to switch it out).
SEE ALSO:if1
LASTMOD :lbfb           :12may14
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