diff --git a/src/frontend/com_fft.c b/src/frontend/com_fft.c
index ced012d4e..3e001ba94 100644
--- a/src/frontend/com_fft.c
+++ b/src/frontend/com_fft.c
@@ -14,7 +14,6 @@ Author:   2008 Holger Vogt
 
 #include "com_fft.h"
 #include "variable.h"
-#include "missing_math.h"
 
 void
 com_fft(wordlist *wl)
@@ -27,106 +26,111 @@ com_fft(wordlist *wl)
     struct dvec  *f, *vlist, *lv = NULL, *vec;
     struct pnode *names, *first_name;
 
-    float *reald, *imagd;
-    int size, sign, isreal;
-    float scaling;
+    double *reald, *imagd;
+    int size, sign, order;
+    double scale, sigma;
 
     if (!plot_cur || !plot_cur->pl_scale) {
         fprintf(cp_err, "Error: no vectors loaded.\n");
         return;
     }
-    if (!isreal(plot_cur->pl_scale) || 
+    if (!isreal(plot_cur->pl_scale) ||
         ((plot_cur->pl_scale)->v_type != SV_TIME)) {
         fprintf(cp_err, "Error: fft needs real time scale\n");
         return;
     }
 
-		
     tlen = (plot_cur->pl_scale)->v_length;
     time = (plot_cur->pl_scale)->v_realdata;
     span = time[tlen-1] - time[0];
     delta_t = span/(tlen - 1);
-    
-    // size of input vector is power of two and larger than spice vector
+
+    /* size of input vector is power of two and larger than spice vector */
     size = 1;
     while (size < tlen)
         size *= 2;
 
-    // output vector has length of size/2
-    fpts = size/2;    
+    /* output vector has length of size/2 */
+    fpts = size/2;
 
-    // window function   
+    /* window functions - should have an average of one */
     win = (double *) tmalloc(tlen * sizeof (double));
     {
        char   window[BSIZE_SP];
        double maxt = time[tlen-1];
-       if (!cp_getvar("specwindow", VT_STRING, window)) 
+       if (!cp_getvar("specwindow", VT_STRING, window))
            strcpy(window,"blackman");
        if (eq(window, "none"))
           for(i=0; i<tlen; i++) {
-             win[i] = 1;
+             win[i] = 1.0;
           }
        else if (eq(window, "rectangular"))
-           for(i=0; i<tlen; i++) {
+          for(i=0; i<tlen; i++) {
              if (maxt-time[i] > span) {
-                win[i] = 0;
+                win[i] = 0.0;
              } else {
-                win[i] = 1;
+                win[i] = 1.0;
              }
           }
-       else if (eq(window, "hanning") || eq(window, "cosine"))
+       else if (eq(window, "triangle") || eq(window, "bartlet") || eq(window, "bartlett"))
           for(i=0; i<tlen; i++) {
              if (maxt-time[i] > span) {
-                win[i] = 0;
+                win[i] = 0.0;
              } else {
-                win[i] = 1 - cos(2*M_PI*(time[i]-maxt)/span);
+                win[i] = 2.0 - fabs(2+4*(time[i]-maxt)/span);
              }
           }
-       else if (eq(window, "hamming"))
+       else if (eq(window, "hann") || eq(window, "hanning") || eq(window, "cosine"))
           for(i=0; i<tlen; i++) {
              if (maxt-time[i] > span) {
-                win[i] = 0;
+                win[i] = 0.0;
              } else {
-                win[i] = 1 - 0.92/1.08*cos(2*M_PI*(time[i]-maxt)/span);
+                win[i] = 1.0 - cos(2*M_PI*(time[i]-maxt)/span);
              }
           }
-       else if (eq(window, "triangle") || eq(window, "bartlet"))
+       else if (eq(window, "hamming"))
           for(i=0; i<tlen; i++) {
              if (maxt-time[i] > span) {
-                win[i] = 0;
+                win[i] = 0.0;
              } else {
-                win[i] = 2 - fabs(2+4*(time[i]-maxt)/span);
+                win[i] = 1.0 - 0.46/0.54*cos(2*M_PI*(time[i]-maxt)/span);
              }
           }
-       else if (eq(window, "blackman")) {
-          int order;
-          if (!cp_getvar("specwindoworder", VT_NUM, &order)) order = 2;
-          if (order < 2) order = 2;  /* only order 2 supported here */
+       else if (eq(window, "blackman"))
           for(i=0; i<tlen; i++) {
              if (maxt-time[i] > span) {
                 win[i] = 0;
              } else {
-                win[i]  = 1;
+                win[i]  = 1.0;
                 win[i] -= 0.50/0.42*cos(2*M_PI*(time[i]-maxt)/span);
                 win[i] += 0.08/0.42*cos(4*M_PI*(time[i]-maxt)/span);
              }
           }
-       } else if (eq(window, "gaussian")) {
-          int order;
-          double scale;
-          extern double erfc();
+       else if (eq(window, "flattop"))
+          for(i=0; i<tlen; i++) {
+             if (maxt-time[i] > span) {
+                win[i] = 0;
+             } else {
+                win[i]  = 1.0;
+                win[i] -= 1.93*cos(2*M_PI*(time[i]-maxt)/span);
+                win[i] += 1.29*cos(4*M_PI*(time[i]-maxt)/span);
+                win[i] -= 0.388*cos(6*M_PI*(time[i]-maxt)/span);
+                win[i] += 0.032*cos(8*M_PI*(time[i]-maxt)/span);
+             }
+          }
+       else if (eq(window, "gaussian")) {
           if (!cp_getvar("specwindoworder", VT_NUM, &order)) order = 2;
           if (order < 2) order = 2;
-          scale = pow(2*M_PI/order,0.5)*(0.5-erfc(pow(order,0.5)));
+          sigma=1.0/order;
+          scale=0.83/sigma;
           for(i=0; i<tlen; i++) {
              if (maxt-time[i] > span) {
                 win[i] = 0;
              } else {
-                win[i] = exp(-0.5*order*(1-2*(maxt-time[i])/span)
-                                       *(1-2*(maxt-time[i])/span))/scale;
+                win[i] = scale*exp(-0.5*pow((time[i]-maxt/2)/(sigma*maxt/2),2));
              }
           }
-	   } else {
+       } else {
           fprintf(cp_err, "Warning: unknown window type %s\n", window);
           tfree(win);
           return;
@@ -148,7 +152,7 @@ com_fft(wordlist *wl)
                 continue;
             }
             if (!isreal(vec)) {
-                fprintf(cp_err, "Error: %s isn't real!\n", 
+                fprintf(cp_err, "Error: %s isn't real!\n",
                         vec->v_name);
                 vec = vec->v_link2;
                 continue;
@@ -166,12 +170,12 @@ com_fft(wordlist *wl)
             ngood++;
         }
     }
-    free_pnode_o(first_name); /* h_vogt 081206 */
+    free_pnode_o(first_name);
     if (!ngood) {
        tfree(win);
        return;
     }
- 
+
     plot_cur = plot_alloc("spectrum");
     plot_cur->pl_next = plot_list;
     plot_list = plot_cur;
@@ -189,7 +193,7 @@ com_fft(wordlist *wl)
     f->v_realdata = freq;
     vec_new(f);
 
-    for (i = 0; i<fpts; i++) freq[i] = i*1./span*tlen/size;
+    for (i = 0; i<fpts; i++) freq[i] = i*1.0/span*tlen/size;
 
 
     tdvec = (double  **) tmalloc(ngood * sizeof(double  *));
@@ -200,7 +204,7 @@ com_fft(wordlist *wl)
        f = alloc(struct dvec);
        ZERO(f, struct dvec);
        f->v_name = vec_basename(vec);
-       f->v_type = SV_NOTYPE; //vec->v_type;
+       f->v_type = SV_NOTYPE;
        f->v_flags = (VF_COMPLEX | VF_PERMANENT);
        f->v_length = fpts;
        f->v_compdata = fdvec[i];
@@ -208,63 +212,61 @@ com_fft(wordlist *wl)
        vec = vec->v_link2;
     }
 
-
     sign = 1;
-    isreal = 1;
-    
-    reald = (float*)tmalloc(size*sizeof(float));
-    imagd = (float*)tmalloc(size*sizeof(float));
-    
-    printf("CPU: Delta Freq %f Hz, input length %d, output length %d\n", 1./span*tlen/size, size, fpts);
-   
+
+    printf("FFT: Time span: %g s, input length: %d, zero padding: %d\n", span, size, size-tlen);
+    printf("FFT: Freq. resolution: %g Hz, output length: %d\n", 1.0/span*tlen/size, fpts);
+
+    reald = (double*)tmalloc(size*sizeof(double));
+    imagd = (double*)tmalloc(size*sizeof(double));
     for (i = 0; i<ngood; i++) {
         for (j = 0; j < tlen; j++){
-    	    reald[j] = tdvec[i][j]*win[j];
-            imagd[j] = 0;
-        }            
+            reald[j] = tdvec[i][j]*win[j];
+            imagd[j] = 0.0;
+        }
         for (j = tlen; j < size; j++){
-    	    reald[j] = 0;
-            imagd[j] = 0;
-        }  
-                 
-        fftext(reald, imagd, size, sign);
-        scaling = 0.3;
-            
+            reald[j] = 0.0;
+            imagd[j] = 0.0;
+        }
+
+        fftext(reald, imagd, size, tlen, sign);
+        scale = 0.66;
+
         for (j=0;j<fpts;j++){
-	    fdvec[i][j].cx_real = reald[j]/scaling;
-	    fdvec[i][j].cx_imag = imagd[j]/scaling;
-        }    		
+            fdvec[i][j].cx_real = reald[j]/scale;
+            fdvec[i][j].cx_imag = imagd[j]/scale;
+        }
     }
-        
     tfree(reald);
     tfree(imagd);
-    
+
     tfree(tdvec);
     tfree(fdvec);
-    tfree(win);    
+    tfree(win);
 }
 
 
-static void fftext(float* x, float* y, long int n, int dir)
+static void fftext(double* x, double* y, long int n, long int nn, int dir)
 {
 /*
    http://local.wasp.uwa.edu.au/~pbourke/other/dft/
    download 22.05.08
    Used with permission from the author Paul Bourke
-*/   
+*/
 
 /*
-   This computes an in-place complex-to-complex FFT 
+   This computes an in-place complex-to-complex FFT
    x and y are the real and imaginary arrays
    n is the number of points, has to be to the power of 2
+   nn is the number of points w/o zero padded values
    dir =  1 gives forward transform
-   dir = -1 gives reverse transform 
+   dir = -1 gives reverse transform
 */
 
    long i,i1,j,k,i2,l,l1,l2;
    double c1,c2,tx,ty,t1,t2,u1,u2,z;
    int m=0, mm=1;
-   
+
    /* get the exponent to the base of 2 from the number of points */
    while (mm < n) {
        mm *= 2;
@@ -292,20 +294,20 @@ static void fftext(float* x, float* y, long int n, int dir)
    }
 
    /* Compute the FFT */
-   c1 = -1.0; 
+   c1 = -1.0;
    c2 = 0.0;
    l2 = 1;
    for (l=0;l<m;l++) {
       l1 = l2;
       l2 <<= 1;
-      u1 = 1.0; 
+      u1 = 1.0;
       u2 = 0.0;
       for (j=0;j<l1;j++) {
          for (i=j;i<n;i+=l2) {
             i1 = i + l1;
             t1 = u1 * x[i1] - u2 * y[i1];
             t2 = u1 * y[i1] + u2 * x[i1];
-            x[i1] = x[i] - t1; 
+            x[i1] = x[i] - t1;
             y[i1] = y[i] - t2;
             x[i] += t1;
             y[i] += t2;
@@ -315,7 +317,7 @@ static void fftext(float* x, float* y, long int n, int dir)
          u1 = z;
       }
       c2 = sqrt((1.0 - c1) / 2.0);
-      if (dir == 1) 
+      if (dir == 1)
          c2 = -c2;
       c1 = sqrt((1.0 + c1) / 2.0);
    }
@@ -323,8 +325,8 @@ static void fftext(float* x, float* y, long int n, int dir)
    /* Scaling for forward transform */
    if (dir == 1) {
       for (i=0;i<n;i++) {
-         x[i] /= n;
-         y[i] /= n;
+         x[i] /= nn; /* don't consider zero padded values */
+         y[i] /= nn;
       }
    }
 }
diff --git a/src/frontend/com_fft.h b/src/frontend/com_fft.h
index 1a3a55656..0989953b8 100644
--- a/src/frontend/com_fft.h
+++ b/src/frontend/com_fft.h
@@ -10,6 +10,6 @@ extern void free_pnode_o(struct pnode *t);
 
 void com_fft(wordlist *wl);
 
-static void fftext(float*, float*, long int, int);
+static void fftext(double*, double*, long int, long int, int);
 
 #endif