subroutine av_write(flag,output_file,fre,buf1,buf2,buf3,nf,
     #          sv,sn,se,nfft,f1,f0,f2,jmin,jmax,ierr)
c
c FLAG = 0
c main output : writes file with average H/V ratios
c
c FLAG = 1
c writes optional output file with average Fourier spectra
c output file name is "output_file"_sp
c
c originally written by Fortunat Kind (avhv_write.f)
c modified by a.tento 05/03 v.1.0
c a.tento 02/04 v.1.0 --> more 
c
        implicit none
        character*200 output_file
        real sv, sn, se, buf1, buf2, buf3, fre, f1, f0, f2
        integer ierr, jmin, jmax, nf, nfft, flag
        dimension  sv(nfft), sn(nfft), se(nfft), fre(nf),
     #             buf1(nf), buf2(nf), buf3(nf)
c
        include 'main.h'
        include 'parameters.h'
        include 'window.h'
c
        character fnout*200, row*200
        integer  j1, nunit ,l, jlen, nfa, iflu, iflc, i

c
        ierr = 0
        fnout = output_file 
        if ( flag  .ne.  0 ) then
        j1 = jlen(fnout)
        fnout(j1 + 1:j1 + 3) = '_sp' 
        endif
c
        call glun(nunit,ierr)
        if (ierr .eq. 1) then
        write (*,*) ' ERROR: AV_WRITE: can not find free unit number'
        ierr=1
        return
        endif
c
        open(unit=nunit,file=fnout,status='unknown')
c
        if ( flag  .eq.  0 ) then
        write(nunit,*) ' ### data used in the H/V ratio processing:'
        else
        write(nunit,*) ' ### data used in the FOURIER spectra',
     #  'processing:'
        endif
c
        do  1 l = 1, n_windows 
        row=data_file(l)
        j1 = jlen(row)

        write(nunit,10) row(1:j1),start_time(l), end_time(l),
     &  idV(l), idN(l), idE(l), idsta(l)

1       continue
 10     format(1x,'# ',a,' ',2f13.2,4(1x,a3))

*       copy the parameter definitions
        write(nunit,'(1x,a)') '#'
        write(nunit,*) '# parameters actually used in the processing:'
        write(nunit,'(1x,a)') '### section processing'
        write(nunit,21) freq_spacing
        write(nunit,22) offset_rem
        write(nunit,23) taper
        write(nunit,25) smooth
        write(nunit,26) merge_type
        write(nunit,29) single_win_out
        write(nunit,30) average_spectra_out
        write(nunit,'(1x,a)') '### end processing'
        nfa= jmax-jmin +1 
        if(nfa  .ne.  nf) write(nunit,300)
 
21      format(1x,'# freq_spacing:',a)
22      format(1x,'# offset_rem:',a)
23      format(1x,'# taper:',a)
24      format(1x,'# instrument_resp:',a)
25      format(1x,'# smooth:',a)
26      format(1x,'# merge_type:',a)
27      format(1x,'# single_component:',a)
28      format(1x,'# average_type:',a)
29      format(1x,'# single_win_out:',a)
30      format(1x,'# average_spectra_out:',a)
300     format(' # WARNING : output frequency limits have been changed',
     #         ' by the smoothing procedure')

c check on units and components labels
c
        iflu = 0
        iflc = 0
        do 17 i = 2, n_windows
        if ( kunits(i)  .ne. kunits(i-1) ) iflu = 1
        if ( kv(i)  .ne.  kv(i-1) ) iflc = 1
        if ( kn(i)  .ne.  kn(i-1) ) iflc = 1
        if ( ke(i)  .ne.  ke(i-1) ) iflc = 1
17      continue
        if ( iflu .ne. 0 ) then
        ierr = 2
        if (flag .eq. 0) write(*,*)' WARNING :',
     #                   ' UNITS label is not the same for all files'
        write(nunit,301)
301     format(' # WARNING : UNITS label is not the same for all files')
        endif 
        if ( iflc .ne. 0 ) then
        ierr = 2
        if (flag .eq. 0) write(*,*)' WARNING :',
     #  ' COMPONENT labels are not the same for all files'
        write(nunit,302)
302     format(' # WARNING : COMPONENT labels are not the',
     #                ' same for all files')
        endif 
c en of the check on units and components labels
c
        write(nunit,'(1x,''#'',30(''-''))') 
        write(nunit,'(1x,''# n_windows: '',i6)') n_windows
        write(nunit,'(1x,''# window_len: '',f10.3)')rmaxwl
        write(nunit,127)kunits(1),kv(1),kn(1),ke(1)
127     format(1x,'# labels: ', 4(1x,a12)) 
        if ( flag .eq. 0 ) then
        write(nunit,123) nfa, f0, f1,f2
123     format(1x,'# n_freq_samples: ',i6,'  Fo: ',f9.4,
     #  ' range +/- 1 s.d.: ', f9.4,' - ', f9.4,' [Hz]')
        write(nunit,350)
350     format(' #    freq           av_HV           ',
     #  'ns_HV           ew_HV       av_HV_logstd    ',
     #  'ns_HV_logstd    ew_HV_logstd')
        else
        write(nunit,124) nfa
124     format(1x,'# n_freq_samples: ',i6)
        write(nunit,360)
360     format(' #    freq          vert_sp           ',
     #  'ns_sp           ew_sp         vert_SD           ',
     #  'ns_SD           ew_SD')
        endif
c
        do 2 l = jmin, jmax
        write(nunit,40) fre(l), 
     #                  buf1(l), buf2(l), buf3(l),
     #                  sv(l), sn(l), se(l)
2       continue
40      format(7(1x,g15.7))

        close(nunit)
        return

      end