Digital Voice Conversion Method

Digital Voice Conversion Method

Developed by: Joseph A Cardani

Objective

A method to recover digital voice on public safety APCO-25, ProVoice and Aegis digital radio systems.

Process

A communication receiver’s 10.7 MHz IF is mixed with a constant signal from an RF generator to produce an RF signal that is directly connected to the antenna input of an APCO P-25 or M/A-COM ProVoice/Aegis capable 2-way radio. This will allow digital voice decoding of any signal that is tuned on the communications receiver.

Benefits

• The method is not band dependent – any channel that can be tuned by the communications receiver can be decoded. Other methods, such as a dedicated 2-way radio, can only operate on 800 MHz, UHF, etc.
• The 2-way digital radio provides excellent specifications and vocoding versus a consumer grade scanner.
• Trunk tracking is not performed by the 2-way radio; it is done by 3rd party software. This bypasses any legal issues with the equipment vendor. In addition, the 2-way radio is programmed conventionally with transmit disabled so there is no risk of accidentally transmitting on the frequency.

Components

Communications Receivers:

• ICOM R-7000 or R-7100 or R-8500 or R-9000 (all have 10.7 IF output)

NovaSource M2 RF Generator: http://www.nova-eng.com

• NS2-0800104 for 800 MHz operation
• NS2-0320104 for UHF operation

Minicircuits Coaxial Frequency Mixer: http://www.minicircuits.com

• ZAD-2 for 800 MHz operation (rated to 1 GHz)
• ZAD-1 for UHF operation (rated to 500 MHz)