Use an old Motorola analog AMPS cellular phone and an external frequency transverter to transmit over someone's cellular phone conversation.
By using a standard Motorola cellular phone (in TESTMODE) as a low-power signal source (825-850 MHz), with the microphone enabled, and an easy to construct frequency transverter, you can talk over someone else's cellular phone.
A Motorola phone in TESTMODE has an option to enable carrier (transmit) on any of the cellular channels between 825 and 850 MHz, with the standard 30 kHz spacing. By using this as a signal source and mixing it with a simple 45 MHz crystal clock oscillator, you can then transmit on any of the cellular phone's RECEIVE frequencies between 870 and 895 MHz. The transmit audio option (microphone enable) will then allow you to modulate the new transmit frequency, usually with rude comments.
The unsuspecting target will hear your voice overriding their current cellular phone conversation. It won't, or shouldn't, cause the target's phone to hang-up).
A high power RF amplifier should be added for maximum effect. The normal RF power amplifier in an old cellular phone will work in a pinch, as will the antenna.
See this section for more information on programing Motorola phones in TESTMODE.
- Cellular Phone Talker-Over - Picture 1 Transverter connected to a Motorola TeleTAC 200. The TeleTAC's power amplifier module is disabled and the 825-850 MHz RF output is taken from the module's RF input.
- Cellular Phone Talker-Over - Picture 2 Transverter overview. 825-850 MHz RF input on the bottom left TNC connector, 870-895 MHz RF output on the top left BNC connector. RF output is only a few milliwatts.
- Cellular Phone Talker-Over - Picture 3 Closeup of the mixer and 45 MHz clock oscillator (LO). First IF amplifier and bandpass filter also shown.
- Cellular Phone Talker-Over - Picture 4 Closeup of RF amplifiers and 880 MHz bandpass filters. The filters are from the duplexer section of old Motorola handset cellular phones.