Modify a simple 49 MHz baby monitor to transmit on a non-standard frequency to prevent accidental detection.

49 MHz baby monitors commonly operate on these following frequencies:

Channel A      49.83 MHz
Channel B      49.845 MHz
Channel C      49.86 MHz
Channel D      49.875 MHz
Channel E      49.89 MHz

The baby monitor's transmitter typically uses a crystal in the 16 MHz range followed by a multiplication-by-3 buffer/amplifier circuit.  Example, a 16.61 MHz crystal is used to transmit at 49.83 MHz.  By replacing this crystal, with a non-standard frequency of say 16.0 MHz, the baby monitor will then transmit on a frequency (48 MHz) which can not be received on any other baby monitor receiver.  This will prevent accidental detection by anyone without a clue.  Use a regular commercial FM communications receiver to receive your new signal.

Pictures

• 49.83/49.86 MHz Baby Monitor Transmitter - Pic 1  Outside case and antenna view.
• 49.83/49.86 MHz Baby Monitor Transmitter - Pic 2  Close-up picture of the new 16 MHz crystal.