correct writing memory channels below 50MHz in radios with hacked firmware

uvk5.py

@@ -571,6 +571,11 @@ def _find_band(self, hz):
         B = BANDS_NOLIMITS
     else:
         B = BANDS
+
+    # currently the hacked firmware sets band=1 below 50MHz
+    if self.FIRMWARE_NOLIMITS and mhz < 50.0:
+        return 1
+
     for a in B:
         if mhz >= B[a][0] and mhz <= B[a][1]:
             return a