INTRODUCTION TO DIGITAL VOICE MODES

INTRODUCTION TO DIGITAL VOICE MODES
IN AMATEUR RADIO By Darrell Davis KT4WX ARRL Technical Specialist

If you like this program: Fall asleep with your head forward If you dislike this program: Fall asleep with your head backward. All the heads should be forward when I am finished :-) - Ed Hare W1RFI, 2001

PROGRAM OUTLINE I. HISTORY OF DIGITAL COMMUNICATIONS II. WHAT IS DIGITAL VOICE III. DIGITAL VOICE MODES OVERVIEW IV. DIGITAL VOICE USAGE IN THE WEST CENTRAL FLORIDA SECTION

I. HISTORY OF DIGITAL COMMUNICATIONS Digital Communications through Amateur Radio has been around since the 1950's. It is called Radio Teletype – RTTY. Originally done with surplus teletype machines. Today digital communications are facilitated with the personal computer.

I. HISTORY OF DIGITAL COMMUNICATIONS With the introduction of the personal computer in the late 1970's communications with personal computers via amateur radio took off.

I. HISTORY OF DIGITAL COMMUNICATIONS Packet Radio came out in 1982 with the first TNC-1 by Tucson Amateur Packet Radio. The TNC used 300 bits per second on HF and bits per second on FM and above 50 MHz. Other digital modes came into amateur radio in the 1980's as well.

I. HISTORY OF DIGITAL COMMUNICATIONS Amateur radio operators began to send still images by Slow Scan TV (SSTV). By 1990 the following digital communications modes were being used in amateur radio: RTTY, SSTV, ASCII, AMTOR, and Packet Radio.

I. HISTORY OF DIGITAL COMMUNICATIONS With the advent of the IBM PC Compatible computer and the sound card in the late 1990's many new digital modes came into existence. This no longer required an external modem between a computer and the radio.

I. WHAT IS DIGITAL VOICE? By the early 2000s the following new digital communications modes were in existence: PSK31 and MFSK16. Many more numerous digital communications modes have come into existence as new sound card modes are developed. New modes required only new software!!

I. HISTORY OF DIGITAL COMMUNICATIONS All these digital modes, with the exception of 50 MHz and above, were restricted by FCC rules to 300 bits per seconds and one bit per symbol or 300 baud. As a result the digital modes and the computers of the 1980's and early 1990's were suitable for keyboard communications, small text files, or small images, not voice transmission.

I. HISTORY OF DIGITAL COMMUNICATIONS THESE DIGITAL COMMUNICATIONS MODES WERE NOT SUITABLE FOR DIGITAL VOICE MODES!! The bandwidth, bit rate, and symbol rate were simply inadequate, due to the technology available and FCC rule limitations.

I. HISTORY OF DIGITAL COMMUNICATIONS In the 1960's Narrow Band Frequency Modulation (NBFM) became common place on 50 MHz and above and was proliferated in the 1970's with the introduction of NBFM voice repeaters.

I. HISTORY OF DIGITAL COMMUNICATIONS In the 1960's Narrow Band Frequency Modulation (NBFM) became common place on 50 MHz and above and was proliferated in the 1970's with the introduction of NBFM voice repeaters. When NBFM signals get weak the signal begins to have a fading or “picket fence” sound if mobile.

I. HISTORY OF DIGITAL COMMUNICATIONS In the mid to late 1990's with the introduction of Digital Signal Processors it became possible to create a data stream from an analog signal, human voice or sounds. It was determined that digital voice needed a minimum of bits per second in order to work properly.

I. HISTORY OF DIGITAL COMMUNICATIONS First amateur radio digital voice communications mode was D-STAR. Developed with government funding by the Japan Amateur Radio League in 1999 and openly published in 2001.

I. HISTORY OF DIGITAL COMMUNICATIONS In 2004, ICOM manufactured the first commercially available digital voice transceiver: ICOM 2200H (2 Meters only) with the optional UT-118 digital module.

I. HISTORY OF DIGITAL COMMUNICATIONS ICOM followed with the first monoband digital voice handhelds, then a dual band handheld, and finally a dual band mobile.

I. HISTORY OF DIGITAL COMMUNICATIONS Moe Wheatley, AE4JY wrote a paper for the Southeastern VHF Society annual conference describing a prototype homebrew D-Star radio. Project page: Paper:

II. WHAT IS DIGITAL VOICE? Digital Voice: Human voice or sounds are converted from analog to a digital data stream and then transmitted to a receiving station where the process is reversed.

II. WHAT IS DIGITAL VOICE? Analog to Digital Conversion Frequency Modulation of Data Stream Power Amplification Digital Voice Transmitter Simple Block Diagram Digital to Analog Conversion Frequency Demodulation of Data Stream Front End Filtering and Amplification Digital Voice Receiver Simple Block Diagram

II. WHAT IS DIGITAL VOICE? Advantages: No mobile flutter – full quieting. Allows simultaneous transmission of other data: text, GPS coordinates, etc. Disadvantages: Cliff effect – When signal to noise ratio is insufficient, decoding stops. Analog will go further and can be received better in some circumstances.

II. WHAT IS DIGITAL VOICE? Terms to Know: Bit Rate – how many bits per second in a transmission Symbol Rate – how many bits per symbol (pieces of information). Baud Rate – roughly how symbols per second. Modulation – method of modulation onto carrier.

II. WHAT IS DIGITAL VOICE? Terms to Know: FDMA – Frequency Division Multiple Access. TDMA – Time Division Multiple Access. Vocoder – encodes analog to digital and digital to analog.

III. DIGITAL VOICE MODES OVERVIEW Digital amateur radio modes of the past sent text only and did not require much bandwidth or fast data rate. Faster data rates would be required to make digital voice a reality. Multiple bits per symbol would be necessary.

III. DIGITAL VOICE MODES OVERVIEW There are five digital voice standards in use in amateur radio at the moment. They are: D-Star P25 NXDN DMR Yaesu System Fusion

III. DIGITAL VOICE MODES OVERVIEW Developed in 1999 and 2000 by Japan Amateur Radio League and published in 2001. There are two modes in D-Star standard: Digital Voice (DV) Digital Data (DD)

III. DIGITAL VOICE MODES OVERVIEW D-STAR Digital Voice – DV Bandwidth: Khz channel. Modulation: 2 Phase Gaussian Minimum Shift Keying (GMSK). Bit Rate: bits per second (3600 for voice data) Symbol Rate: 2 bits per symbol. Vocoder: AMBE (DVSI)

III. DIGITAL VOICE MODES OVERVIEW D-STAR Digital Data – DD (1296 MHz and up) Bandwidth: KHz. Modulation: 2 Phase Gaussian Minimum Shift Keying (GMSK). Bit Rate: kbps. Symbol Rate: 2 bits per symbol. Had the option of doing 10Mbps on 10GHz backbone link – advanced at the time.

III. DIGITAL VOICE MODES OVERVIEW D-STAR D-Star Sound: Equipment Availability: Commercially manufactured equipment available through only mostly Icom and one radio currently by Kenwood as of 2016.

III. DIGITAL VOICE MODES OVERVIEW P25 development was fostered by a committee of the Association of Pubic-Safety Communications Officers (APCO). Phase 1 standard released in 2005 and Phase 2 standard released in

III. DIGITAL VOICE MODES OVERVIEW APCO Project 25 (P25) Designed in order to facilitate sending extra data (GPS Coordinates, text, etc.) along with a voice data stream to improve public safety communications and standardize communications between pubic-safety entities. Standard is open and published. There are eight standards in the P25 specification.

III. DIGITAL VOICE MODES OVERVIEW APCO Project 25 (P25) Phase 1: 12.5 Khz channel FDMA Continuous 4 Level Frequency Modulation (C4FM), or Compatible Differential Offset Quadrature Phase Shift Keying (CQDPSK). 9600 bits per second 2 bit symbol rate. Vocoder – IMBE (DVSI) Non repeater – simplex only.

III. DIGITAL VOICE MODES OVERVIEW APCO Project 25 (P25) Phase 2: 12.5 Khz channel TDMA (Time Slices) Modulation: Compatible Offset Quadrature Phase Shift Keying (DCQPSK). 12000 bits per second 2 bit symbol rate. Vocoder – AMBE+ (DVSI)

III. DIGITAL VOICE MODES OVERVIEW FDMA verses TDMA

III. DIGITAL VOICE MODES OVERVIEW APCO Project 25 (P25) Phase 3 (Trunked): Still under development.

III. DIGITAL VOICE MODES OVERVIEW P25 P25 Sample Sounds: Equipment Availability: Available only currently as new or surplus equipment through commercial manufacturers (Motorola, Uniden, Kenwood, Icom, etc.) but very expensive. Surplus more affordable.

III. DIGITAL VOICE MODES OVERVIEW Digital Mobile Radio (DMR) Tier I and Tier II standards were first published in 2005 and the Tier III standards published in 2012. Standards were fostered by the European Telecommunications Standards Institute (ETSI) and consists of four standards.

III. DIGITAL VOICE MODES OVERVIEW DMR – Digital Mobile Radio Tier I: Designed for HTs and limited to ½ watt. Tier II (conventional radio): 12.5 Khz channel TDMA (2 Time Slot) 6.25 Khz per time slot equivalent. 9600 bits per second. Continuous 4 Level Frequency Modulation. 4 bits per symbol

III. DIGITAL VOICE MODES OVERVIEW DMR – Digital Mobile Radio TDMA Slot Timing Diagram

III. DIGITAL VOICE MODES OVERVIEW DMR – Digital Mobile Radio Tier III (trunked radio): Supports trunked radio system including some TCP/IP capability. Same specifications of modulation and bit rate as Tier II.

III. DIGITAL VOICE MODES OVERVIEW DMR – Digital Mobile Radio Like P25 Phase 2, DMR is TDMA not FDMA. TDMA allows two users to occupy one 12.5 KHz narrowband channel (now the new wideband). It complies with the narrowband 6.25 Khz (2.5 Khz deviation) FCC requirement for Part 90 users as of 1/01/13 by providing two time slices per transmission.

III. DIGITAL VOICE MODES OVERVIEW DMR – Digital Mobile Radio DMR Sample Sound: Equipment Availability: Equipment available through commercial manufacturers but there are inexpensive DMR Radio now available through the Chinese two way radio manufacturers (Hytera, Tytera, Tait, etc.)

III. DIGITAL VOICE MODES OVERVIEW DMR verses P25 Phase 2: DMR and P25 Phase 2 are not interchangeable. DMR uses four different frequency shifts in its implementation of C4FM. DMR uses different data frames than P25 does. However both standards are open and published.

III. DIGITAL VOICE MODES OVERVIEW DMR – Digital Mobile Radio DMR Sample Sound: Equipment Availability: Equipment available through commercial manufacturers but there are inexpensive DMR Radio now available through the Chinese two way radio manufacturers (Hytera, Tytera, Tait, etc.)

III. DIGITAL VOICE MODES OVERVIEW Standards developed by Yaesu in This standard is proprietary but the standard has been published.

III. DIGITAL VOICE MODES OVERVIEW Yaesu System Fusion 12.5 Khz channel Continuous 4 Level Frequency Modulation (C4FM). 9600 bits per second 4 bit symbol rate. Vocoder – AMBE+ (DVSI)

III. DIGITAL VOICE MODES OVERVIEW Yaesu System Fusion Has Four Modes of Operation: Analog FM Voice-Data simultaneous Mode Voice Full Rate Mode Data Full Rate Mode

III. DIGITAL VOICE MODES OVERVIEW Yaesu System Fusion Analog FM: Straight analog FM Mode

III. DIGITAL VOICE MODES OVERVIEW Yaesu System Fusion Voice/Data simultaneous mode: Runs voice and data concurrent. Each mode takes 6.25 Khz of the channel or ½ of channel.

III. DIGITAL VOICE MODES OVERVIEW Yaesu System Fusion Voice Full Rate Mode: Runs voice data on the whole 12.5 Khz channel. Higher quality voice transmission.

III. DIGITAL VOICE MODES OVERVIEW Yaesu System Fusion Data Full Rate Mode: Runs digital data on the whole 12.5 Khz channel. All digital data only.

III. DIGITAL VOICE MODES OVERVIEW Yaesu System Fusion AMS – Automatic Mode Selection. In this mode the radio listens and switches automatically to mode that was heard within 1-2 seconds

III. DIGITAL VOICE MODES OVERVIEW Yaesu System Fusion Yaesu System Fusion Sample Sound: Equipment Availability: Only Yaesu makes commercially available Yaesu System Fusion radios. Used gear does turn up at good prices.

III. DIGITAL VOICE MODES OVERVIEW SUMMARY OF DIGITAL VOICE MODES Source: “Untangling Digital Voice above 50 MHz” Bob DeMattia, K1IW – QST April 2015 Type Codec Modulation Sharing Access P25 Phase 1 NXDN D-STAR DMR P25 Phase 2 System Fusion IMBE AMBE+2 AMBE 4-FSK 2-GMSK FDMA TDMA 12-bit NAC 6-bit RAN Call Signs Color Codes

III. DIGITAL VOICE MODES OVERVIEW NXDN The standard was developedin a join venture by Icom and Kenwood between 2003 and The Kenwood brand is Nextedge and the Icom brand is IDAS. 12.5 Khz channel, FDMA access, and C4FM Modulation.

III. DIGITAL VOICE MODES OVERVIEW NXDN Has two 6.25 Khz narrowband channels in a Khz channel. Standard was publically made available in Equipment Available: Must purchase commercially made equipment through Icom or Kenwood and prices are still high.

III. DIGITAL VOICE MODES OVERVIEW Homebrew and 3rd Party Digital Voice Options Wirelss Holdings LLC: DV4Mini, DV4Home, and DVMobile – Low power USB transceiver stick, home based and mobile multimode digital voice modems.

III. DIGITAL VOICE MODES OVERVIEW Homebrew and 3rd Party Digital Voice Options MMDVM – Mulit Mode Digital Voice Modem: Takes two commercial radios and turns them into a mulit mode digital voice repeater. Software still in development.

IV. DIGITAL VOICE USAGE IN THE WEST CENTRAL FLORIDA SECTION D-Star: Used to be widespread. Now only one left in Pasco as of last information. DMR: Predominant in Charlotte and Sarasota Counties. Some in Polk County Yaesu System Fusion: Predominant in Desoto, Manatee, and Pasco Counties. One in Polk County. Coming in Hardee County. APCO Project 25: A few in Pasco, Pinellas, and Polk County. NXDN: NI4CE Repeater System.

Questions? Discussion? Thank you for your attention and participation!!

CONTACT INFORMATION Darrell Davis KT4WX 6350 Mills Road Fort Meade, FL (863) Website:

INTRODUCTION TO DIGITAL VOICE MODES

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