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DARS: Distributed Amateur Radio Station

NOTE: This subject is in the early stages of development. Expect it to change substantially and often.


  • SDR Primer – the basics of Software Defined Radio for Amateurs
  • SDR in action – my experience with Software Defined Radio

The Idea

The Distributed Amateur Radio Station is a direct development from Software Defined Radio (SDR). The reasoning behind its conception is:

  1. In the not-too-distant future, all new amateur radio sets will be software-defined; analog design will go the way of vacuum tubes. (This trend has already begun.)
  2. By its nature, software can be loosely coupled. Whereas analog circuit components (stages) are tightly coupled by electrical currents of specific magnitude and frequency, software componants are coupled through digital data passed via a communications medium.
  3. Communications media can take many forms. One thing they all have in common is that they can work over variable distances, ranging from nanometers to kilometers.
  4. By using suitable communications media with the necessary speed and capacity, the components of a software defined radio can be located at a distance from each other. That is, components can be distributed across a communications network.
  5. Distribution means that, given appropriate protocols and interfaces, the components of a radio can be located wherever it's convenient to do so, and can be assembled via software into a working radio.
  6. The actual physical form a radio takes will be dictated mostly by the circumstances in which it is to be used – portable, base, etc. The “circuits-in-a-box” paradigm becomes optional.
  7. The concept can be extended to encompass an entire Amateur radio station.
  8. In this scenario, a station would be a networked computer system with analog peripherals, rather than a collection of hardware conneced by wires.

One way to think about this is that it is the architecture of a distributed computing system applied to an Amateur radio station. The system could be fully self-contained, open to the Internet, or some combination of the two.

Of course, a distributed station still must have hardware: RF components (transmitters, receivers, antennas), and user interfaces (keys, mics, computers, speakers). But its heart is composed of software running on computers.

Implications

The big idea here is that the pieces of a distributed station are connected together not electrically, but rather by data. The essential requirement of systems connected by data is that they both understand the form and format of the data being conveyed between them. That means some form of data standards that both systems can apply independently in order to communicate.

Think of cell phones. They are, at base, radio transceivers. The cellular network works because phones and towers are programmed to use standard protocols. That lets you buy a new phone, put in a sim card, and immediately start using the network. The Internet works the same way, with an unlimited number of unique systems bound together by standard protocols.

No such standards exist for Amateur Radio equipment – as anyone who has tried to connect a rig to a computer can testify. That means a system of standards would have to be developed. The object would be to enable station components to communicate with each other regardless of make and model.

To my mind, the possibilities of such a system seem boundless. Think of some of that already are being realized:

  • Flex and Apache Labs offer transceivers that have no built-in controls – user control is via software running somewhere else on a network.
  • RemoteRig makes a system that connects a radio's control head to its base units via a TCP/IP network, making it possible to locate them any distance apart.
  • USB SDR dongles (such as RTL-SDR) take RF from an antenna, digitize it, and place it on the USB bus of a computer for additional processsing – which may include forwarding to a TCP/IP port.
  • WebSDR is a Software-Defined Radio receiver connected to the Internet, allowing many listeners to listen and tune it simultaneously.
  • Some external speakers incorporate digital signal processing (DSP) in the form of audio-frequency filters that operate independently of the radio.

The first two, although partially distributed, suffer from being closed systems, using proprietary hardware and software.

The SDR dongles and online SDR receivers better inllustrate the potential of a distributed station, in that they can be combined with any external system that can handle the data they produce (a computer, in this case).

The loudspeakers with DSP are somewhat less clear-cut. Viewing the DSP section as three blocks – analog-to digital coverter, digital processor, digital-to-analog converter – reveals its distributed nature. Those blocks could be implemented independently and be physically separated, connected via data transfer over a network. Here is an example.

  • A receiver could convert analog audio to digital and output that data directly to the network. (An SDR receiver could output digital audio directly.)
  • A DSP unit could receive the data and process it, placing the resulting data on the network.
  • A loudspeaker with a digital interface could receive the processed data, convert it to analog, and send it to its drivers to produce sound waves.

How Would a Distributed Station Work?

Basic Concepts

The essential aspect of DARS is that it separates station operator functions from the hardware that makes up a station. That is, station hardware is controlled not by manipulating direct physical controls (knobs, buttons) that are part of the electrical circuit, but indirectly, through a computer. A second aspect is that some of the hardware can be entirely replaced by a computer – not just its controls.

The station operator has two primary functions:

  • Information transfer: what we send and receive over the air.
  • Station control: how it is sent and received.

[NOTE: Partial entry; still under development]

darsmaster.txt · Last modified: 2019/06/12 20:30 by headgod