Tuesday, July 27, 2021

"New" P-25 TDMA Control Channel In Use

This is not federal or military specific, but interesting none the less. 

A recent discovery of a new type of P-25 trunking control channel has sparked some developments in the various monitoring and analysis software solutions. 

It seems that a couple of new Harris P-25, phase 2 trunked radio systems for energy companies have started using the same TDMA modulation for the control channel data as is used for the voice frequencies. Traditionally, the control channels in P-25 phase 2 trunked systems have used FDMA modulation for the control channel data. This is potentially a big change for all P-25 trunked system monitoring, although it appears to be an option for newer systems that are being built out now and is not likely to start showing up on existing public safety radio systems.

Here is the Radio Reference forum thread with more specific information on what was found:


The Bluetail Technologies forum also seems to indicate they have added TDMA control channel support for their SDR receivers:


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