8- Advanced radio modes

8-Advanced radio modes

Digital Audio modes

Digital Modes were originally designed for professional use, where the radio was preset by admin staff so that the user could not change channels, talk groups, etc. For an amateur radio user, this both increases the flexibility, as they are the admin, and increases the complexity too! But it is well worth learning. A professional radio is not always a better choice. It’s a bit like driving a Formula 1 car on a normal road: it would stall, need a team of mechanics to start the engine, be very noisy, and way too fast, as they are hard to drive below 100 Mph!

Many radio systems can be made more robust and audio more readable by digitising the signal. This reduces interference and allows better audio within the same bandwidth.

DMR – A digital system developed by Motorola, the most popular mode.

Photo: an MSI 2500 SDR (not very good) and a Heltec V3 Meshtastic/Meshcore digital transceiver (license free)

It can also allow two simultaneous transmissions at the same time due to a thing called time interleaving. This alternates between signal A and signal B but compresses each signal in time and causes a slight delay in the received transmission, but it’s barely noticeable.

They can also split or isolate users into different Talk Groups (TG); these are often themed around geography or other themes.

There is Colour or Colour. Simply put, it is just an extra way of grouping users, and generally they go from 1 to 5. Is that confusing or what! Think of it like the plug-in coloured radio crystals for tuning model radio controllers.

Other modes include - D-Star, M17, NXDN, P25, System Fusion (C4FM)

The advantage of digital modes is that a repeater or digital node can provide access to many Talk Groups, Colour Codes and Time Slots all at the same time and still at a better quality (in theory anyway) than FM. That said it can sound robotic if not perfectly aligned.

Digital modes

By splitting the 2.5 kHz audio bandwidth into channels approximately 50 Hz wide (varies by mode) and sending short digital signals like SMS text messages generally 15 characters long (FT8), the recipient can decode these at a much lower signal-to-noise ratio to the extent that the signal can be 20 dB under the noise and still be decoded in FT8. There are many digital modes, and each has one or more strengths. Much of the decoding was developed for radio astronomy, where very weak signals need to be assessed accurately.

They are valuable resources in

Testing propagation over time and different bands, comparing antennas, competing to get all States, Countries or other parameters. They’re a great learning tool!

Overview of some modes

FST4 – for VLF and Satellite

FT2/FT4/FT8 general use

JT4 - satellite

JT9/JT65 - general

Q65/MSK144 -4m upwards, satellite

Satellite includes moonbounce (EME earth-moon-earth), meteor scatter

WSPR – whisper, the quietest mode. Ideal at very low power, i.e., milliwatts!

It’s a transmit-only mode, though your station can also report to wsprNet.info
https://www.wsprnet.org/drupal/WSPRnet/map?destination=WSPRnet/map

The idea is to transmit in sequence on various bands and repeat at different times of the day. This allows you to see the changes in propagation over hours, days, bands and is the most informative. Many stations operate a separate transmitter and computer just for this.

Digital Nodes (some analog ones exist now too)

With a Raspberry Pi Zero 2 W or better and a modem card* you can make a link from a digital radio to the internet and walk around the house and garden transmitting just 50 mW to your node and work with people all over the world. The modem card takes your radio signal and converts it from whatever mode your radio is in to an internet protocol. There are many options like PI-Star, WSPD, HubNet. There are plenty of videos on YouTube for these.

https://www.pistar.uk/

https://w0chp.radio/wpsd/?trk=public_post-text

https://www.hubnetwork.uk/index.php/more/build-your-own-node

Talkgroup TG 91 worldwide (though mostly USA) goes berserk around 3 pm every Sunday!

TG 235, 2350,1,2,3,4 are UK groups, but there are hundreds

SSTV/ATV – Slow Scan Television / Amateur Television

If you hear this signal, it sounds like an old FAX machine. It is used to send low-res colour images 320x240 or 640x480, usually a QSO card, often a novelty picture or cartoon with minimal text on. Then there the cherished ISS, International Space Station QSO cards run occasionally and are very collectable as they change each time.

Satellites

The ISS – International Space Station

Operates in a number of modes, mostly as a VHF/UHF repeater, sometimes as a radio station where you talk to the astronauts, and sometimes as an SSTV station.

The callsign denotes which crew is running the station: NA1SS for the United States, RS0ISS for Russia, and various European callsigns like DP0ISS and OR4ISS. These callsigns are used by crew members to contact ground control and for amateur radio communications

Amateur Radio Satellites – OSCAR (Orbiting Satellites Carrying Amateur Radio)

Contrary to popular belief, you do not need a lot of power or a massive antenna to contact the ISS or many other satellites. It can be done on FM mode with a 5-watt walkie-talkie and a lot of patience. Different antennas will help as will knowing when it is coming over. Many Apps like Heavens Above (Android) or https://www.amsat.org/track/ (web) help.

Ideally, use either two radios (one VHF and one UHF) or a true duplex radio so you can hear your own signal coming back. Some radios will automatically change frequency to combat the Doppler effect. (The UHF frequency changes a few kHz as it passes over; the VHF is less affected and can be ignored)

The Arrow antenna is one of the best, but it’s a great opportunity to build your own.

The primary callsign for the International Space Station (ISS) is NA1SS. Other callsigns used include RS0ISS for Russia and DP0ISS for Europe.

https://www.ariss.org/contact-the-iss.html

If you have an SDR and a computer/laptop, you can autotune using Gpredict or other tracking software and record your QSOs.

There is a lot more than I can cover here on getting contacts, but plenty of videos on YouTube for each satellite!

Weather FAX and Satellites

Not amateur radio, but a great pastime. Sadly, the NOAA analogue satellites are dead now, but Meteor digital weather satellites can be decoded using software like SatDump and an SDR. Most can be received on 137 Mhz and a SAWbird preamp and SAW filter are recommended.

Weather Fax, or WEFAX, exists on several frequencies, including HF. You can decode it with FLDigi or other software.

https://www.dxsoft.com/en/products/seatty/

https://weatherfax.com/stations/