Digital Voices

Digital Voices – The Formats Presently Being Used in Public Safety and Amateur Radio

APCO P25 Phase I is the present version that is in used across the country for Digital Public Safety, the P25 “open” standard has been reworked by some manufacturers limiting some of the standardization that the P25 was hoped to present..

P25 Phase I has the ability to function as a analog system or digital system.

P25 Presently operates via FDMA (Frequency Division Multiple Access) with the plan for P25 Phase II to use TDMA (Time Division Multiple Access), P25 Phase II will also have the capability to “roll-back” to FDMA for “conventional emergency operations.”

D-STAR is a Amateur Radio system which offers digital voice and data communication. It connects repeater sites over microwave links and the Internet and forms a wide area Amateur Radio network.

The D-STAR system provides a new capability and functionality to the Amateur Radio world and increases the efficiency of emergency communications.

D-STAR provides digital voice at 4k8 baud and data is available via 1.2GHz at a rate up to 128kbps via GMSK modulation – Gaussian Mask Shift Keying,

On VHF and UHF digital voice plus 950bps data can coexist on the same channel.

At the present time only Icom is making transceivers with D-STAR capability. With experimentation one can modify other transceivers for D-STAR Connectivity.

Fixed Base (i.e. repeaters) do not have analog capabilities – Strictly Digital Only.

Mobile/Porable D-STAR enabled equipment have both analog and digital capabilities.

MotoTRBO(tm) MotoTRBO is a product of Motorola with the primary market being Industrial-Business Sector. MotoTRBO is designed to operate digital only on a single 12.5kHz channel by slicing the digital transmissions into time slots thus creating to available channels via TDMA (Time Division Multiple Access).

Data throughput is 2k0 per time slot.

MotoTRBO has analog capability (repeaters can be programmed to operate analog or digital, mobiles and portables can operate analog and digital).

NXDN was designed by Icom and Kenwood primarily for the Industrial-Business Sector.

NXDN is marketed by Icom as IDAS (Icom Digital Advanced System) and Kenwood as NEXEDGE. With channels at true 6.25kHz channel spacing using FDMA (Frequency Division Multiple Access).

NXDN provides 9k6 @ 8.3kHz bandwidth and 4k8 @ 4kHz bandwidth.

NXDN is compatible with analog systems thus making migration from analog to digital easier. Some of the companies participating in NXDN equipment development include: Daniel Electronics, Icom, Kenwood and Ritron among others.


Digital Intertie Communication Enhancement (DICE) is mobile communications package designed for interoperability between analog and digital networks as well as diverse communications systems. DICE will fit in with the Communications Transportable System (CoTS) concept for Rapid Deployment Operations (RaDeO).

Forward-thinking Digital Imagining

1) HSMM capabilities at least in the 70cm band and even in 1.25m band.

2 ) Long range HSMM networks with data/video/voice capabilities. (With products like the Ubiquiti Networks Bullet[] should be able to get some decent range)

3) Low-cost Digital Interface that can plug into any radio with a data port (most new radios have a data port present, plus by regulation {at least for Part 90 equipment} they have to be able to handle at least 4k8 baud data – definitely not high speed, but it lets messaging take place).

4) Compact Rapid Deployment Links (RaDL) based on Asterisk that can be quickly delivered to any location thus providing phone and radio connectivity. ** Come up with a way to do it with the Gumstix Overo boards everything could fit in a radio. Add a Ethernet pigtail on the back of the radio one would have access to local SIP/IAX2 phone capabilities plus the radio could provide long-haul capabilities for at least one call to the outside world. Instant dispatch capabilities with the package too, along with intertie to other radio systems.**

The radio itself would work as a link/remote base anyone in the local network could connect through the LAN/wLAN to the RF side to transmit/receive via the radio itself. Plus they would still have local network capabilities. Since the original gumstix/Asterisk package was able to handle 10 to 15 calls, the new package should be able to increase that by at least (to 15 to 20 calls). Attach another wLAN to the RaDL would create another sub-network as well as capability for a second RF Gateway channel.



Digital Analog Radio Network

Send In Most Potentially Linkable Exchange

With the diversity of both digital and analog systems available today a way to connect them together is needed.  Through the development of Digital Analog Radio Network (DARN) methods will be presented that complete the interconnectivity and interoperability necessities.

May DARN be found as a way “to mend by weaving thread across a gap” in technology.