diff --git a/chprintf.c b/chprintf.c
index 5b3d24e..9859eee 100644
--- a/chprintf.c
+++ b/chprintf.c
@@ -87,8 +87,8 @@ static char *
 ulong_freq(char *p, uint32_t freq, uint32_t precision)
 {
   uint8_t flag = FREQ_PSET;
-  if (precision == 0)
-    flag|=FREQ_PREFIX_SPACE;
+  flag|= precision == 0 ? FREQ_PREFIX_SPACE : FREQ_NO_SPACE;
+
   if (precision == 0 || precision > MAX_FREQ_PRESCISION)
     precision = MAX_FREQ_PRESCISION;
   char *q = p + MAX_FREQ_PRESCISION;
@@ -132,11 +132,6 @@ ulong_freq(char *p, uint32_t freq, uint32_t precision)
 
   // Get string size
   uint32_t i = (b - q);
-  // Limit string size, max size is - precision
-  if (precision && i > precision) {
-    i = precision;
-    flag |= FREQ_NO_SPACE;
-  }
   // copy string
   // Replace first ' ' by '.', remove ' ' if size too big
   do {
@@ -150,6 +145,8 @@ ulong_freq(char *p, uint32_t freq, uint32_t precision)
         c = *q++;
     }
     *p++ = c;
+    if (!(flag & FREQ_PSET) && precision-- == 0)
+      break;
   } while (--i);
   // Put pref (amd space before it if need)
   if (flag & FREQ_PREFIX_SPACE && s != ' ') 
diff --git a/plot.c b/plot.c
index 17fc7fb..4635149 100644
--- a/plot.c
+++ b/plot.c
@@ -480,7 +480,8 @@ value(const float v)
     return v + 90.0 + 20.0*LOG_10_SQRT_50;
     break;
   case U_VOLT:
-    return pow(10, (v-30.0)/20.0) * sqrt(50.0);
+//  return pow(10, (v-30.0)/20.0) * sqrt(50.0);
+    return pow(10, (v-30.0)/20.0)*SQRT_50;
 //    return pow(10, v/20.0) * POW_SQRT;      //TODO there is an error in this calculation as the outcome is different from the not optimized version
     break;
   case U_WATT:
@@ -498,13 +499,16 @@ to_dBm(const float v)
   switch(setting.unit)
   {
   case U_DBMV:
-    return v - 30.0 - 20.0*log10(sqrt(50));
+//  return v - 30.0 - 20.0*log10(sqrt(50));
+    return v - 30.0 - 20.0*LOG_10_SQRT_50;
     break;
   case U_DBUV:
-    return v - 90.0 - 20.0*log10(sqrt(50.0));
+//  return v - 90.0 - 20.0*log10(sqrt(50.0));     //TODO convert constants to single float number as GCC compiler does runtime calculation
+    return v - 90.0 - 20.0*LOG_10_SQRT_50;
     break;
   case U_VOLT:
-    return log10( v / (sqrt(50.0))) * 20.0 + 30.0 ;
+//  return log10( v / (sqrt(50.0))) * 20.0 + 30.0 ;
+    return log10( v / (SQRT_50)) * 20.0 + 30.0 ;
     break;
   case U_WATT:
     return log10(v*1000.0)*10.0;
@@ -849,7 +853,7 @@ static void trace_get_value_string(
   (void)freq;
   (void) point_count;
   float v;
-  char buf2[11];
+  char buf2[16];
   char buf3[8];
   buf2[0]=' ';
   uint32_t dfreq = 0;
@@ -895,7 +899,7 @@ static void trace_get_value_string(
     }
 #endif
   } else {
-#if 1
+#if 0
   uint32_t resolution = get_sweep_frequency(ST_SPAN);
   if (resolution  <= 2000*POINTS_COUNT)
     plot_printf(&buf2[1], sizeof(buf2) -1, "%3.3f" , (dfreq + 500) / 1000000.0);
@@ -905,7 +909,7 @@ static void trace_get_value_string(
     plot_printf(&buf2[1], sizeof(buf2) -1, "%3.1f" , (dfreq + 50000) / 1000000.0);
   }
 #else
-  plot_printf(&buf2[1], sizeof(buf2) -1, "%.8qHz" , dfreq);
+  plot_printf(&buf2[1], sizeof(buf2) -1, "% 8.3qHz" , dfreq);
   }
 #endif
     v = value(coeff[i]);