; REFREQ
;---------------------------------------------------------------
;! Specifies the frequency to be uased as the reference
;# ADVERB SPECTRAL ANALYSIS
;-----------------------------------------------------------------------
;;  Copyright (C) 2020
;;  Associated Universities, Inc. Washington DC, USA.
;;
;;  This program is free software; you can redistribute it and/or
;;  modify it under the terms of the GNU General Public License as
;;  published by the Free Software Foundation; either version 2 of
;;  the License, or (at your option) any later version.
;;
;;  This program is distributed in the hope that it will be useful,
;;  but WITHOUT ANY WARRANTY; without even the implied warranty of
;;  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;;  GNU General Public License for more details.
;;
;;  You should have received a copy of the GNU General Public
;;  License along with this program; if not, write to the Free
;;  Software Foundation, Inc., 675 Massachusetts Ave, Cambridge,
;;  MA 02139, USA.
;;
;;  Correspondence concerning AIPS should be addressed as follows:
;;         Internet email: aipsmail@nrao.edu.
;;         Postal address: AIPS Project Office
;;                         National Radio Astronomy Observatory
;;                         520 Edgemont Road
;;                         Charlottesville, VA 22903-2475 USA
;-----------------------------------------------------------------------
REFREQ    LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC
----------------------------------------------------------------
REFREQ
Type:  Adverb  (Scalar)
Use:   Specifies the frequency to be used for the reference
Null value:  0 -> found from the data
Tasks:
   HOLOG....Read & process holography visibility data to telescope
            images.   REFREQ is the reference in GHz.
   SOUSP....Fits source spectral index from SU table or adverbs.
            REFREQ specifies the reference in GHz, 0 -> 1 GHz,
            < 0 -> data header frequency
   SPIXR....Fits spectral indexes to each row of an image incl
            curvature.  REFREQ specifies the reference in GHz,
            0 -> 1 GHz, < 0 -> data header frequency
----------------------------------------------------------------