P25 Radio Phase 1 C4FM Theory

In this video I go over the process involved in transmitting and receiving a P25 digital voice signal. This version of P25 uses an analog radio to send digitized voice audio over the air using 4 different deviation levels to represent 4 different 2 bit pairs.

[@notsrynot]

This is a great video! Super helpful explanation and kinda hard to find content on this type of P25 modulation method

[@zouhirbelbaki1399]

thanks for this video

[@dc95811]

You're welcome.

[@marcaziz8936]

what is the reference you used for this information please

[@dc95811]

A Google search of "P25 packet structure" is how it starts. I created the drawings in the video and did the math examples. I have been aware of C4FM since Skytel paging in the 90's. The AMBE speech coding is created by a private company, and is a world to themselves. The P25 standards are established by an official group.