Section 3.7: Digital and Video Modes #
Welcome to the digital age of amateur radio! If voice modes are like having a conversation, digital modes are like sending text messages or emails through the airwaves. And video? You might be surprised to know that it’s been possible to send pictures and even television via Amateur Radio for decades!
Packet Radio #
Imagine sending an email through radio waves. That’s essentially what packet radio does! It breaks your message into small “packets” of data, sends them over the air, and then reassembles them at the receiving end. Each packet includes:
- A checksum for error detection
- The call sign of the destination station
- An automatic repeat request if errors are detected
It’s like sending a puzzle through the air that reassembles itself perfectly on the other side! Packet radio was a big deal in the 1980s and 1990s before the internet became widespread. Today, it’s still used in some applications, especially in emergency communications. Think of it as the sturdy old pickup truck of digital modes—not the fastest, but reliable and it gets the job done.
APRS (Automatic Packet Reporting System) #
APRS is like the social media of ham radio. It lets you transmit all sorts of data: your position, weather info, short messages—you name it! Imagine a real-time map showing where hams are operating, complete with status updates. It’s super useful for public service events or emergencies, letting coordinators see where their operators are at a glance. With APRS, you can:
- Track your location as you move around
- Set up a home station as a digital signpost
- Share local weather data
- Send short text messages
- View a map showing the locations of other stations
It’s like Twitter meets Google Maps, but for radio!
PSK31 #
PSK31 is like the smooth jazz of digital modes. It’s designed for real-time, keyboard-to-keyboard conversations. PSK stands for “Phase Shift Keying,” and the “31” in its name comes from its bandwidth—just 31 Hz! That’s incredibly narrow, allowing it to get through in tough conditions.
RTTY (RadioTeletype) #
RTTY is the granddaddy of digital modes. It’s been around since the 1930s! Think of it as a radio-based typewriter. It’s still popular in contests and among some news agencies.
PACTOR #
PACTOR is like the Swiss Army knife of digital modes. It can automatically switch between speeds and encoding methods based on conditions. There are several versions, with PACTOR III offering robust performance for things like email over radio.
Digital Mobile Radio (DMR) #
Think of DMR as the multitasking wizard of the radio world. This digital mode uses a nifty trick called time-division multiple access (TDMA). What does that mean for you? Well, it splits a single 12.5 kHz channel into two separate time slots, allowing two conversations to happen at once on the same frequency. It’s like getting double the channels without needing more spectrum!
Here’s what makes DMR stand out:
- Color Codes: Instead of using PL tones or DCS codes like in analog systems, DMR repeaters use color codes. To get on a DMR repeater, you’ve got to match the right color code—think of it as a digital key to unlock access.
- Talkgroups: DMR organizes users into talkgroups, which are basically like radio chat rooms. Just program the right group ID, and you’re chatting with other hams in that group, whether they’re around the corner or around the world.
DMR radios are usually configured by installing a “code plug” into the radio. The code plug is actually just software configuration containing access information for repeaters and talk groups.
DMR is popular in both the amateur and commercial radio worlds, and with its efficient use of spectrum and robust features, it’s no wonder why.
D-STAR (Digital Smart Technologies for Amateur Radio) #
D-STAR, which stands for Digital Smart Technologies for Amateur Radio, is a digital voice and data protocol developed specifically for amateur radio by the Japan Amateur Radio League (JARL). It was one of the first digital modes designed for amateur use and remains popular among hams who appreciate its versatility and features.
D-STAR enables both voice and data communications, allowing operators to send text, images, and GPS data alongside their voice transmissions. One of the standout features of D-STAR is its ability to connect repeaters via the internet, enabling global communication without the need for HF bands.
D-STAR operates exclusively in the 2-meter, 70-centimeter, and 1.2 GHz amateur bands. Within these bands, you can take advantage of D-STAR’s unique functions, such as:
- Call Sign Routing: D-STAR allows users to direct their communications to specific call signs, making it easier to connect with other hams across the globe. Because of this, the first thing you must do before you can use a D-STAR digital transceiver is program in your call sign – that call sign will be sent with every transmission.
- Digital Data: Besides voice, D-STAR supports low-speed data transfer, which can be used for text messaging or even telemetry.
The primary radio manufacturer that supports and promotes D-STAR is Icom. Icom was the first company to produce D-STAR compatible radios and continues to be a leading advocate of the technology, offering a range of transceivers and equipment designed to make the most of D-STAR’s capabilities.
To use D-STAR, you’ll need a compatible transceiver and either a local D-STAR repeater or else a hot-spot (see below).
System Fusion (C4FM) #
System Fusion, also known as C4FM, is a digital communication mode developed by Yaesu. It was designed to provide the flexibility of both digital and analog FM communications in one system, making it easy for users to transition between modes depending on their needs.
System Fusion offers several key features:
- Automatic Mode Select (AMS): This feature allows System Fusion radios to automatically switch between digital and analog modes depending on the incoming signal. This makes it easier for operators to communicate without worrying about manually changing settings.
- Digital Group Monitor (GM): This feature lets you see who else is within range and operating on the same frequency. It’s particularly useful for group activities or emergencies.
- Data Capabilities: In addition to voice, System Fusion supports data transmission, such as text messaging, GPS information, and even images.
System Fusion repeaters can operate in both digital and analog modes, providing greater flexibility for local clubs and groups. System Fusion can connect to the internet via Wires-X, Yaesu’s network of linked repeaters and nodes.
Digital Mode Hot Spots #
A digital mode hot spot is like your personal gateway to the world of digital radio. Imagine having your own miniature repeater that connects your transceiver to digital networks via the internet. Whether you’re using DMR, D-STAR, or System Fusion, a hot spot extends your reach far beyond the local area, letting you chat with hams across the globe without leaving your shack.
Hot spots are perfect for those who don’t have a local repeater nearby or want the flexibility to operate from anywhere with an internet connection. Just connect your transceiver to the hot spot, and you’re ready to explore the world of digital modes without limits.
SSTV (Slow Scan Television) #
SSTV is like sending a postcard via radio. It transmits still images, taking anywhere from a few seconds to a couple of minutes to send a single picture. You can even receive pictures from the International Space Station!
FSTV (Fast Scan Television) #
FSTV is full-motion video over the air. Think of it as YouTube for ham radio! It requires a lot of bandwidth, so it’s typically used on UHF and higher frequencies. The NTSC (National Television System Committee) standard, which was used for analog TV in North America, is also used in amateur television. Just remember, as fun as it is, broadcasts intended for the general public are forbidden. Any transmissions you make, including Amateur Television, need to be for an allowed purpose in the Amateur Radio service.
Mesh Networks #
Mesh networks are like a web of interconnected radios. Each station in a mesh network can receive and relay data, creating a robust, decentralized network. It’s based on standard Wi-Fi equipment with custom firmware and relies on the same IEEE 802.11 modes as a traditional wireless network, just modified a bit. Imagine a whole neighborhood linked together, able to communicate even if the internet goes down!
New Digital Modes #
The world of digital modes is constantly evolving. Modes like FT8 and FT4, developed by Joe Taylor, K1JT, have revolutionized weak signal communication. These modes can pull readable signals out of noise levels that would make voice communication impossible.
Most of these digital modes interface with your computer using audio input and output (line in and speaker out, usually) from a sound card on your computer plus some way to control the PTT. Often, you also have a serial port to talk to the radio which handles the PTT and can also control the radio (set the frequency, etc) using a method called CAT (Computer-Aided Transceiver) control. Many options exist, so long as you have those three things at minimum: Audio in, audio out, and transmitter keying.
There are also interfaces that plug into your USB port and provide both the audio interface and the serial interface for an “all in one” interface experience!
WSJT-X is a software suite that includes digital modes like FT8, FT4, and JT65. These modes are digital weak signal modes, perfect for making contacts when conditions are poor. They support things like moonbounce (EME), meteor scatter, and other weak signal propagation methods. They have become popular in recent years because they are so easy to use to communicate long distances, though the amount of information conveyed mostly limits you to contesting. This is just one of the many software packages you can use for things like this – but it’s popular enough that it’s mentioned on the exam!
ARQ #
ARQ (Automatic Repeat reQuest) is a clever error correction method. If a receiving station detects an error, it automatically asks for a retransmission. It’s like having a built-in “Could you repeat that?” function.
Getting Started with Digital Modes #
As a Technician, you have access to many of these digital modes, especially on VHF and UHF bands. They open up a whole new world of possibilities:
- Experiment with packet radio for emergency communications.
- Try SSTV to exchange pictures with other hams.
- Dip your toes into HF digital modes on 10 meters when conditions allow.
- Set up a simple FSTV station on the UHF bands.
- Explore DMR for clear digital voice communications.
- Get involved with your local ham radio mesh network.
Remember, one of the exciting things about ham radio is that it’s always evolving. New modes are being developed all the time, pushing the boundaries of what’s possible with radio communication.
Whether you’re into casual chats, technical experiments, emergency preparedness, or even space communication, there’s a digital mode out there for you. It’s like having a massive toolbox—each mode is a different tool, suited for different jobs.
So don’t be afraid to experiment! Set up your computer, connect it to your radio, and dive into the digital world. You might just find yourself making contacts across the country (or the world) with nothing more than a simple wire antenna and some clever software.
Welcome to the cutting edge of amateur radio—where hobby meets high-tech!