Lesson #1 – What is D-Star? D-Star University Lesson #1 – What is D-Star?

In the days before D-Star… When two or more people wanted to talk, they could turn on their radios, pick a frequency and chat via analog simplex.

Of course, that doesn’t always work… Sometimes the distances are too great, or there are obstacles in the way.

So we use repeaters! A repeater re-transmits the signal between users, allowing people to talk over greater distances and around obstacles.

Repeaters can be linked…. Two or more repeaters can be linked together, either over the air or through an internet connection. A group of repeaters linked together is known as a “reflector”.

Repeaters can be linked…. Reflectors can cover world-wide areas. You may have heard or spoken on local analog repeaters that are connected to reflectors via EchoLink or IRLP

questions? (up next – history of D-Star)

How did D-Star start? In 1998 the Japanese government funded an effort by the Japan Amateur Radio League (JARL) to develop a new digital communications mode specifically for amateur radio use. In 2001 the D-Star specification was published by JARL. Icom begins selling D-Star capable radios in April 2004.

How did D-Star start? In 2008, Robin Cutshaw (AA4RC) releases DPlus specification, creating the first D- Star reflectors. In 2006 there were 48 D-Star users, by 2009 there are over 10,000 users. Today there are over 50,000. In 2016 the first D-Star satellite was put into orbit (OUFTI-1) Dayton 2016 – Kenwood previews new D- Star capable HT

So how does D-Star work? Every D-Star radio contains an AMBE voice encoder/decoder (vocoder) chip. This chip takes analog speech and converts it into digital information. This chip can also take encoded digital speech and de- code back to analog sound. All D-Star audio is encoded and decoded in the radio. Instead of radio waves carrying analog sound information, they carry ones and zeros. Everything else is the same.

You can use D-Star for simplex…

You can use D-Star on repeaters…

You can even talk across the world on D-Star reflectors!

questions? (up next – digital vs analog signals)

Digital vs Analog Signals – The Waveform Analog signals are transmitted as continuous form waves, while digital signals are transmitted in discrete steps representing one or zero.

Digital vs Analog Signals – Sampling Rate Digital signals are created by ‘sampling’ an analog data source. The sampling rate determines how closely the digital signal matches the analog original. Signals with a high sampling rate will sound closer to the original, but will also consume more data.

Digital vs Analog Signals – Error Correction Analog signals degrade with no way to restore them to original quality. Digital signals can be verified for correctness via checksums and other tools. The signal can then be repaired before being passed on. As a result, digital signals do not ‘fade’, they simply drop out once they can no longer be repaired.

questions? (up next – D-Star vs other modes)

How does D-Star compare? How is voice transmitted? MODE ANALOG or DIGITAL Analog FM Analog IRLP Analog protocol, digital transport EchoLink D-Star Digital DMR Fusion

How does D-Star compare? Can I have my own personal access point, or do I need a repeater? MODE PERSONAL ACCESS POINT? Analog FM No IRLP Very limited EchoLink Yes D-Star DMR Yes* Fusion

How does D-Star compare? Can I create and share my own reflectors? MODE CREATE OWN REFLECTORS? Analog FM No IRLP EchoLink D-Star Yes DMR Yes* Fusion

How does D-Star compare? How wide is the signal? MODE BANDWIDTH Analog FM 12.5 KHz to 25 KHz IRLP EchoLink D-Star 6.25 KHz DMR 12.5 KHz with two timeslots Fusion 12.5 KHz

How does D-Star compare? How does the signal sound? MODE AUDIO QUALITY Analog FM Best IRLP EchoLink D-Star Good DMR Better Fusion

questions? (up next – personal access points)

Personal Access Points What’s that? A way to get onto a reflector without using a repeater. Connects your D-Star radio to the reflector you select using an internet connection. Cheap, easy to build and highly portable access points have driven the explosion of D-Star. Most D-Star QSOs don’t happen on repeaters!

Personal Access Points Do I need one? No. Why would I want one? Because you’re a ham, which means you love hacking stuff! Use D-Star reflectors in the car. Keep in touch over D-Star when travelling. You don’t have to share - connect to what you want, when you want. Can be the cheapest entry point into D-Star

Personal Access Points Two basic types: The Transceiver Type – This type of access point connects your D-Star capable radio to a reflector over the internet. It consists of the transceiver device, a computer to run the transceiver device and an internet connection. This type takes digital D-Star information coming out of your radio and sends it to the reflector.

Personal Access Points Two basic types: The Vocoder Type – This type of access point is used without a D-Star capable radio. The access point device contains the same AMBE vocoder chip as a D-Star radio. Analog audio is taken from a connected computer (via a headset) and digitized in the access point device. The encoded audio is sent to the reflector via an internet connection.

questions? (up next – lesson 2: getting on the air with D-Star)