AIPS HELP file for ICHANSEL in 31DEC18
As of Mon Sep 24 13:01:20 2018
Type: Adverb (REAL, 4 elements x 20 rows)
Use: Data selection adverb used to specify a list of start and stop
channel numbers plus an increment AND IF NUMBER to be used in
some way, such as to be averaged to form a pseudo-continuum
channel. Up to 20 sets of channel numbers/IFs can be specified.
The first two elements specify the start and stop channel
numbers, the third specifies the increment within that range,
i.e.if CHANSEL = 10,20,2 that means take every other channel in
the range 10 - 20, so that channels 10,12,14,16,18,20 would be
averaged together. The fourth element specifies the IF to which
the previous three apply.
Null Value: 0
A completely null value means use all channels in some tasks:
ICHANSEL(1,i) <= 0 => 1
ICHANSEL(2,1) <= 0 => Nchan
ICHANSEL(2,i) <= 0 => (i > 1) -> no more channel sets
ICHANSEL(3,i) <= 0 => 1
ICHANSEL(4,i) <= 0 => all IFs
BPASS, CPASS, AVSPC, REWAY and many other tasks use the center
75 percent of the channels for any IF for which no ICHANSEL was
specified. Other tasks have different defaults including being
unwilling to set defaults.
ICHANSEL = 9,56 includes all channels 9-56 in all IFs
ICHANSEL = 12,53,1,1, 62,116,1,1, 12,116,1,2
includes all channels from 12-53 and
62-116 in IF 1, and all channels from
12-116 in IF 2. If there are more
IFs, default actions are taken.
ICHANSEL = 17,112,1,0, 23,45,1,1, 87,112,1,1
includes all channels from 17-112 in
all IFs except IF 1 which includes
channels 23-45 and 87-112. NOTE
WELL: the all IF instruction must
precede any instruction that
partially overrides it.