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.