Low Frequency Lexicon

Note: Many terms and acronyms used in this activity come from amateur radio or electronics in general. The American Radio Relay League site has good indexes of those words, including 3-letter "Q" signals. If you would like to see any words added to our list, contact the LWCA Webmaster.

AFRICAM: This is a DOS-based program written by VE2IQ to generate and decode BPSK signals at a variety of bit rates. It is currently the only BPSK program that allows GPS synchronization. It is not compatible with all sound cards, and the computer must be booted in DOS mode, not running a DOS box under Windows. Bill has an A/D converter board available that can substitute for the sound card, and the supporting text for AFRICAM contains a wealth of information. Download AFRICAM at Bill de Carle's site, and look through his other programs.

ARGO: An easy to use spectral display program written by I2PHD, aimed at displaying slow speed CW and similar signals. Official download site for ARGO.

Beacon: A long-duration transmitted signal used for checking propagation conditions and receiving setups. Most U.S. "Lowfer" operation in the 160-190 kHz range is done with beacons. The transmitting operator is not generally looking for two-way communications, and is unlikely to be listening while transmitting.

BPSK: Binary Phase Shift Keying. In this mode, the carrier signal remains on, but the phase is shifted by 0 or 180 degrees with ASCII or other codes. A decoding program recognizes the phase shifts and prints letters or symbols on a computer screen. Moderate speed BPSK is used in "PSK31" in amateur radio applications at HF. Because LF propagation is so stable, much lower keying rates may be used, improving the weak signal detection. Data rates for BPSK are frequently quoted in the number of milliseconds for each bit. For example, "MS100" refers to BPSK with bit lengths of 100 milliseconds.

CW: Continous Wave. In common use, this means on/off keying of a carrier signal of constant frequency. The International Morse Code is normally used. This is the most basic communications mode for LF work, though the keying rates are generally much lower than you will encounter in Amateur Radio.

DDS: Direct Digital Synthesis. Refers to generating an RF signal by digital techniques, using a D/A converter at the output. Several manufacturers make chips specifically for this purpose. They may be used to generate very accurate oddball frequencies, as well as do frequency and phase shift keying. DDS chips are used in wireless phones and amateur radio gear.

DFCW: Dual Frequency Continuous Wave. Normal CW keying is on/off, using the International Morse Code, with dots three times longer than dashes. DFCW is an alternative where dot and dash characters are of the same length, but are sent on different frequencies. This permits the use of spectral display software like ARGO, but shortens the amount of time for text to be sent. The letter "X" would look like "- _ _ -" on the screen. DFCW is a form of FSK.

FSK: Frequency Shift Keying. Any form of modulation where the transmitted frequency is changed in steps to send information. RTTY, HELL and DFCW are common examples.

GBPSK: GPS-synced BPSK. This is an informal term referring to BPSK that is sent and received in step with the 1 pulse-per-second time ticks offered by GPS receivers.

GPS: Global Positioning System. While not strictly an LF idea, GPS is used for two principal tasks at LF. First, it may be used to discipline an oven controlled crystal oscillator into providing a very accurate and stable signal. The low data rates used in LF experimentation require knowledge of the transmitted and received frequency down to the milliHertz range, and GPS-controlled oscillators are useful at the very lowest data rates. Second, the 1 pulse-per-second timing outputs of GPS receivers can be used to synchronize the transmission and reception of BPSK signals. This relieves the decoding program of the need to synchronize to the incoming data, as it already knows when a bit is being sent.

Grabber: Short for "Screen Grabber." Some LF receiving enthusiasts run software that takes regular snapshots of what's on their computer screens, and posts them as web pages on the Internet. Armed with the URL, you can see what's being received at someone else's location. This is a very useful tool to keep track of who's on the air, and what the chances are that you can receive them. For transmitting operators, it gives instant signal reports. A list of some of the regular grabber sites is available here.

Grabulator: See "Grabber." Same thing...clever title.

HF: High Frequency. The HF range is from 3 to 30 MHz.

Hifer: This is a recent term referring to unlicensed activity in the 13.553 - 13.567 MHz region under Part 15 of the FCC rules, which permit up to 4 milliwatts into a half-wave dipole in that range. Lowfers who might otherwise spend the summer months listening to static at LF have had considerable success in long-range communication in this Hifer band, using QRSS and similar techniques developed at LF. Due to Doppler shifting and fast fading, the very slowest data rates are not effective. Interest in Hifer operation tends to peak in the spring and summer.

JASON An FSK mode for sending text in a narrow bandwidth at low data rates. Based on a concept developed by Steve Olney, VK6ATO, JASON was written by I2PHD specifically for LF use. Transmitting equipment must either be capable of translating audio frequency up to LF (an SSB exciter) or shifting frequency on command from the program. Official download site for JASON.

LF: Low Frequency. LF refers specifically to the range from 30 kHz to 300 kHz, but some liberties are taken in common use.

LORAN: LOng RAnge Navigation system. The remaining part of a radio navigation system that dates back to the 1940's, LORAN-C operates on 100 kHz. This is a worldwide system of high power stations that transmit fast rise-time groups of pulses. The repetition rate of the pulses is coded to chains of transmitters, so there are multiple sources of the same rates. The fast rise times produce sidebands that extend over 50 kHz either side of 100 kHz. The 135.7 - 137.8 kHz band allocated to amateur radio in some countries is literally full of weak sidebands from LORAN-C. The effect on a spectral display program like ARGO is to clutter the screen with horizontal lines, each representing the Nth harmonic of the LORAN repetition rate from a transmitter near enough to you. A list of the Loran lines appearing in that band within the U.S. is available on the LWCA site. The lines are created by the transmitting process, and are not a result of receiver or preamp overload.

Lowfer: A low frequency experimenter. The term originally applied to people doing transmitting and receiving work in the U.S. "Part 15" band from 160-190 kHz, but now includes licensed LF Amateur and experimental activity.

Medfer: A term applied to operators within the 510 to 1710 kHz range under Part 15 of the FCC rules. Most of the serious long-distance work has been done at the ends of the band, where broadcast station interference is the least. Like Lowfer work, this activity is best suited to the colder months.

MF: Medium Frequency. This covers the 300 kHz to 3 MHz range.

Part 5: Part 5 is the section of the FCC rules that deals with the Experimental service. Licensing under this service is available to individuals and companies that are doing research or designing products and need to radiate RF signals. Applications are submitted on line, and there is a filing fee. There is presently some activity in the U.S. in the 135.7 - 137.8 kHz and 160 - 190 kHz bands by Experimental licensees gathering data and experience to hopefully restart the process for an Amateur Radio LF allocation. FCC Part 5 Rules can be found on-line.

Part 15: FCC Part 15 rules deal with permissable signals that may be radiated intentionally or unintentionally across the whole radio spectrum. No licensing is involved to operate within the Part 15 limits. Within some frequency ranges, considerable signals can be produced. Other countries have similar regulations, but the details vary greatly. For much more information, see the LWCA Web site.

SPECLAB: Spectrum Laboratory is a very powerful audio analysis program written by DL4YHF. It will not only display slow-speed keyed signals like ARGO or SPECTRAN, but will do long-term logging, direction finding, PSK demodulation, and a variety of other things. While this program is not for the "newbie," it is an incredible tool for the experienced user. Official download site for Spectrum Lab.

SPECTRAN: A spectral analysis program written by I2PHD. This is the predecessor to ARGO, and offers a wider range of settings. The user may stick with the preset options, or may customize things according to taste. SPECTRAN is a very flexible program, but new users may want to start with ARGO, which has fewer options. Official download site for SPECTRAN.

Q-signals: "Q-signals" are three letter codes used in Amateur Radio, primarily in CW communication. A list of these codes and their meanings can be found at the ARRL site.

QRSS: This is a recent modification of the long-established "Q" signal "QRS" used in radio communication. QRS refers to the practice of sending CW signals more slowly, usually to allow reception through interference, or by a less experienced operator. "QRSS" came into use among LF experimenters to refer to very slow speed CW communication, where the speed is measured by the number of seconds to send a dot, rather than by the conventional number of words per minute. The fastest common QRSS speed is 3 seconds per dot, and is normally noted as QRSS3. Dot lengths of 10, 20, 30, 60, 90, 120 and 240 seconds are generally used at LF, and are indicated as QRSS10, QRSS20, and so forth. These slow speeds are not intended for copy by ear, but by spectral analysis programs like ARGO, which will show them as slowly formed dots and dashes on a screen. The slowest speeds offer the best weak-signal capability, but information is transferred very slowly, and fading may be an issue.

SVM: Selective Voltmeter. This is actually a receiver, usually tunable over a wide range from audio through radio frequencies. SVM's have traditionally been used by telephone companies to maintain carrier circuits where information was sent over wires at radio frequencies. Some SVM's have very accurate frequency and level readouts, and are used as a primary receiver by LF experimenters. If you see an SVM advertised for second-hand or auction sale, check with an experienced Lowfer to see if it is suitable for your application, as some of the tunable models aren't of much use for high-stability work.

TA: Trans-Atlantic.

TP: Trans-Pacific.

VLF: Very Low Frequency. The VLF range is technically from 3 kHz to 30 kHz, though casual use may cover a wider range.

WOLF: Weak-signal Operation at Low Frequency. This is a mode developed by KK7KA. It uses BPSK at an MS100 data rate to send a 15 character message in a highly error-corrected format. The decoding program can build up copy over a 27 minute period, allowing excellent weak-signal performance. The original program has a command-line interface, and works only from pre-recorded files. The best program for receiving and sending WOLF was written by Wolf Buscher, DL4YHF , and is a Windows "GUI" allowing real-time processing and a variety of data rates. A number of 2-way QSO's have been made with this version.