An Amateur Radio Survival Guide for Linux Users
Maintaining a Linux-only household is getting easier every day. The large number of people working to port or re-implement desktop and general-use software from other operating environments helps keep the progress going. Enjoying a hobby that is mostly dominated by Windows users is, unfortunately, not nearly as easy. The Amateur Radio culture is one of experimentation and going against the mainstream, but the relatively small number of people pushing innovation are doing so on their platform of choice or comfort, which usually means Windows. As a result, many applications are not available for Linux.
In this article, I cover some of the basic tasks that a Linux user venturing into the world of Amateur Radio might be interested in doing without undergoing a significant lifestyle change. First, here's a quick vocabulary lesson for those not familiar with some common radio terms.
The HF (High Frequency) bands are frequencies between about 1.8MHz and 30MHz, starting just above the US AM broadcast radio band. Signals on these frequencies are capable of traveling around the globe, thanks to the upper ionosphere. If you want to talk to another country, these are the bands for you.
The VHF (Very High Frequency) and UHF (Ultra High Frequency) bands are frequencies above 30MHz up to about 3GHz. Signals in this range propagate in an increasingly line-of-sight manner and, thus, are mostly useful for local area (VHF) and very short range (UHF) communication. However, these frequencies also provide an opportunity for increased bandwidths and data rates, which is why Wi-Fi sits at the upper range (2.4GHz).
One popular activity on HF is “contesting”, which involves making long-distance contacts to achieve some sort of goal. This usually involves making as many contacts to different places as possible in a certain period of time. Because it is a contest, some sort of log is needed to record the contacts you make for later submission. Because Amateur Radio operators use call signs to identify each other, most logging software helps identify people you've already “worked” to avoid duplication.
The Xlog program for Linux provides basic contest log functionality, including duplicate checking. It also can interface to your radio via a serial port to record other bits of information about a contact automatically, such as mode, signal strength and frequency. Each contest specifies a different piece (or pieces) of information that must be exchanged between operators, so Xlog has some configurable fields to help with that task (Figure 1).
Another very popular activity on the HF bands is operating the slow-speed digital modes. Some of these modes, such as RTTY (radioteletype), predate modern digital computers. Others, like PSK31 (phase shift keying, 31 baud), are fairly recent inventions that use advanced signal processing to their advantage. Although external hardware (digital and analog) previously was used to operate these modes, it now is very common to use a modern soundcard to encode and decode the signal, much like a modem does for a telephone line.
The most common application for doing this sort of work on Linux today is called Fldigi. With a soundcard, serial port and some interfacing to your radio, you can transmit and receive these digital signals without any significant expense. The Fldigi software supports a large number of operating modes, allowing you to communicate via keyboard-to-keyboard text with other amateur operators around the world.
In addition to conversing directly in real time with other amateurs, you also can use Fldigi to record and report the signals it hears in an autonomous fashion. By leaving your radio on the standard PSK31 calling frequency, Fldigi will listen for and report the call signs and locations it hears to a public database. This is very valuable information when comparing the stations other locals are hearing, given the differences between your locations, antennas and so on. It also gives you an idea of what time of day signals from a particular part of the globe are reaching you, in case you want to contact someone in a specific place. If you're interested in this sort of operation, check out the live map (see Resources) to find out who is hearing whom right now.
Although it may seem quaint and obsolete, if you've never had a half-duplex text conversation at 31 baud with someone on the other side of the world, you don't know what you're missing—double that if you've ever done it with nothing more than a battery, a radio and a piece of wire hung in a tree!
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