diff --git a/crpptbx/TCV/gdat_tcv.m b/crpptbx/TCV/gdat_tcv.m
index b2574ee98ab100a26790d98e1bb2f8c865b298eb..aa1f576bcf1598c075e050fdf9d16f5b66dde3a8 100644
--- a/crpptbx/TCV/gdat_tcv.m
+++ b/crpptbx/TCV/gdat_tcv.m
@@ -994,6 +994,11 @@ elseif strcmp(mapping_for_tcv.method,'switchcase')
 
     %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    case {'mhd'}
+    if isfield(gdat_data.gdat_params,'nfft') && ~isempty(gdat_data.gdat_params.nfft)
+      % used in gdat_plot for spectrogram plot
+    else
+      gdat_data.gdat_params.nfft = 1024;
+    end      
     % load n=1, 2 and 3 Bdot from magnetic measurements
     if shot< 50926
       n1=tdi('abs(mhdmode("LFS",1,1))');
@@ -1060,6 +1065,9 @@ elseif strcmp(mapping_for_tcv.method,'switchcase')
       gdat_data.dim{2} = [1; 2; 3]; 
       gdat_data.dimunits{1} = n1.dimunits{1};
       gdat_data.dimunits{2} = 'n number';
+      if shot>= 50926
+        gdat_data.dimunits{2} = 'n number, at this stage n3=n1';
+      end
       gdat_data.units = 'T/s';
       gdat_data.request_description = 'delta_Bdot from magnetic probes to get n=1, 2 and 3';
       gdat_data.label = {'n=1','n=2','n=3'}; % can be used in legend(gdat_data.label)
diff --git a/crpptbx/TCV/tcv_help_parameters.m b/crpptbx/TCV/tcv_help_parameters.m
index a61d86bf35e3a02ccc2f0f617f1ab7accbfd740e..2278708d719a3c90cf42c2c3f6688f0adc35c489 100644
--- a/crpptbx/TCV/tcv_help_parameters.m
+++ b/crpptbx/TCV/tcv_help_parameters.m
@@ -48,6 +48,7 @@ help_struct_all.camera = ['sxr: for MPX: ''central'', ''top'' (default), ''botto
                     ' for XTOMO: ''central'' (a central chord only), defaults if empty, [1 3 5] if only camera 1, 3 and 5 are desired'];
 help_struct_all.freq = '''slow'', default, lower sampling; ''fast'' full samples for both mpx and xtomo';
 help_struct_all.max_adcs = 'rtc: source=''adcs'' maximum nb of adc channels loaded for each board in each active node';
+help_struct_all.nfft = '512 (default) changes time resolution in spectrogram in gdat_plot for ''mhd'' request';
 
 %help_struct_all. = '';
 
diff --git a/crpptbx/gdat_plot.m b/crpptbx/gdat_plot.m
index 0e13888272da6ef8656fb1f48643efdee1558d42..7493a8a585913826faa2320bd096cb6e67c8d097 100644
--- a/crpptbx/gdat_plot.m
+++ b/crpptbx/gdat_plot.m
@@ -104,7 +104,7 @@ if all(isfield(gdat_data,{'data','t'})) && ~isempty(gdat_data.data) && ~isempty(
     if isfield(gdat_data.gdat_params,'nfft') && ~isempty(gdat_data.gdat_params.nfft)
       nfft = gdat_data.gdat_params.nfft;
     else
-      nfft=1024;
+      nfft=512;
     end
     tmhdm=mean(reshape(gdat_data.t(1:nfft*fix(length(gdat_data.t)/nfft)),nfft,fix(length(gdat_data.t)/nfft)));
     for i=1:size(gdat_data.data,2)