Amateur Radio in Australia (VKFAQ)

Digital Modes used on the HF bands (3-30 MHz)

PK232MBX multi mode controller

Typical of the multimode controllers that became popular in the 80s and 90s, this box contained its own CPU and could receive and transmit a number of digital modes suitable for HF and VHF use. Fed with speaker level audio and producing microphone level output suitable for transmitting, it could convert your ordinary hf voice transceiver into a multimode system capable of Radio teletype (RTTY using baudot code), AMTOR (Amateur standard Teleprinting over Radio), FEC (forward error correcting mode baudot), ASCII, packet radio at several speeds, Morse. In receive mode it could also decode weather fax images and more. Much of this functionality can now be performed by software on personal computers, in conjunction with the computer's sound card.

HF digital modes

Have you ever chatted via keyboard to people over the Internet? If so, you have a fair idea of what it's like to operate via digital modes such as radio teletype, AMTOR and PSK-31. The main difference is that instead of using a phone line or a broadband connection, supported by millions of dollars worth of cabling, routers and undersea cables, multiple ISPs and a lot of support staff, you're using a radio link and connecting directly with the other station via probably several hundred dollars worth of your own radios.

Smart software and sound-card equipped PCs has made it possible for one to link computers to transceivers without needing a sophisticated modem box in between. The result of these developments has been a tremendous growth in modes such as PSK-31. Digital modes take up very little space on the radio bands, much less that what's required for voice communication. This makes it possible for amateurs with low power and restricted antennas to achieve communications not possible with voice modes. PSK-31 is so efficient that an American kit manufacturer has developed a two-watt transmitter that allows world-wide communication from almost anywhere when plugged into a laptop computer. Most PSK-31 activity is around 14.070 MHz, but the mode also has potential for weak signal VHF/UHF work. PSK-31 is most suited for one-on one keyboard communication.

Modes such as AMTOR and PACTOR are other digital modes popular on HF. These are also effective weak signal modes (much more so than packet radio). PACTOR bulletin board systems on HF linked to VHF bulletin boards using packet radio allow stations beyond the reach of VHF packet radio to send and receive messages. An example of such a system is the VK5BAR station operated by the Adelaide Hills Amateur Radio Society.

There is a lot of information available on the internet about these modes and rather than trying to summarise this wide field here, it's suggested you research these modes using your favourite search tools.

Next: VHF Digital modes

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