 #define ACK_TIME   20  // number of milliseconds to wait for an ack
 #define RETRY_LIMIT 9  // maximum number of times to retry
 #define RADIO_SYNC_MODE 2
+#define SCAN_WIDTH 50
 
 /// @details
 /// eeprom layout details

/// @dir RF12tune2
/// This sketch loads a configuration compatible with rf12.cpp and
/// then enters a frequency scanning mode to find the
/// centre of frequency offset from its partner ack'ing Jeenode.
/// 2013-10-04 <john<AT>o-hare<DOT>net> http://opensource.org/licenses/mit-license.php

#define GROUP 209              // Default value 212

    delay(100);
    downLow = 0xFFFF; 
    downHigh = 0;
  for (scan = (frequency_offset + SCAN_WIDTH); scan > (frequency_offset - SCAN_WIDTH); --scan)
  {
   rf12_control(0xA000 + scan); 
   byte good = probe();
