A radio propagation beacon is a radio beacon, whose purpose is the investigation of the propagation of radio signals. Most radio propagation beacons use amateur radio frequencies. They can be found on HF, VHF, UHF, and microwave frequencies. Microwave beacons are also used as signal sources to test and calibrate antennas and receivers.[1][2]
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Most beacons operate in continuous wave (A1A) and transmit their identification (call sign and location). Some of them send long dashes to facilitate signal strength measurement. A small number of beacons transmit Morse code by frequency shift keying (F1A). A few beacons transmit signals in digital modulation modes, like radioteletype (F1B) and PSK31 (G1B).
The International Amateur Radio Union Region 2 (North and South America) bandplan for 160 meters reserves the range 1999 kHz to 2000 kHz for propagation beacons.
Most high frequency radio propagation beacons are found in the 10 meters (28 MHz) frequency band, where they are good indicators of Sporadic E ionospheric propagation. According to IARU bandplans, the following 28 MHz frequencies are allocated to radio propagation beacons:
| IARU Region | Beacon Sub-bands |
|---|---|
| R1 |
|
| R2[3] |
|
| R3 |
|
In the 6 meters (50 MHz) band, beacons operate in the lower part of the band, in the range 50000 kHz to 50080 kHz. In the United States, the Federal Communications Commission (FCC) only permits unattended 6 meter beacon stations to operate between 50060 and 50080 kHz.[4] Due to unpredictable and intermittent long distance propagation, usually achieved by a combination of ionospheric conditions, beacons are very important in providing early warning for 50 MHz openings.
Several countries in ITU Region 1 have access to frequencies in the 70 MHz region, called the 4 meters band. The band shares many propagation characteristics with 6 meters. The preferred location for beacons is 70,000 to 70,030 kHz; however, in countries where this segment is not allocated to Amateur Radio, beacons may operate elsewhere in the band.
Beacons on 144 MHz and higher frequencies are mainly used to identify tropospheric radio propagation openings. It is not uncommon for VHF and UHF beacons to use directional antennas. Frequencies set aside for beacons on VHF and UHF bands vary widely in different ITU regions and countries.
| Band | Beacon Sub-band (MHz) | ||
|---|---|---|---|
| ITU Region 1 | ITU Region 2 | ITU Region 3 | |
| 2 m | 144.400-144.490 | 144.275–144.300 | Unknown |
| 1.25 m | N/A | 222.050–222.060 | N/A |
| 70 cm | 432.800-432.990 | 432.300–432.400 | Unknown |
| 33 cm | N/A | Varies Locally | N/A |
| 23 cm | 1,296.800-1,296.990 | 1,296.070-1,296.080 | Unknown |
| 13 cm | 2,320.800-2,320.990 | 2,304.300-2,304.400 | Unknown |
The beacon sub-bands in the United Kingdom, also reflect IARU Region 1 recommendations.[5]
In addition to identifying propagation, microwave beacons are also used as signal sources to test and calibrate antennas and receivers. SHF beacons are not as common as beacons on the lower bands, and beacons above the 3 centimeters band (10 GHz) are unusual.
| Band | Beacon Sub-band (MHz) | ||
|---|---|---|---|
| ITU Region 1 | ITU Region 2 | ITU Region 3 | |
| 9 cm | 3,400.800-3,400.995 | 3,456.300-3,456.400 | Unknown |
| 5 cm | 5,760.800-5,760.995 | 5,760.300-5,760.400 | Unknown |
| 3 cm | 10,368.800-10,368.995 | 10,368.300-10,368.400 | Unknown |
| 1.2 cm | Beacons are rare | ||
Most radio propagation beacons are operated by individual radio amateurs or amateur radio societies and clubs. As a result, there are frequent additions and deletions to the lists of beacons. There are, however a few major projects coordinated by organizations like the International Telecommunications Union and the International Amateur Radio Union.
The International Beacon Project (IBP), which is coordinated by the Northern California DX Foundation and the International Amateur Radio Union, consists of 18 HF propagation beacons worldwide, which transmit in turns on 14100 kHz, 18110 kHz, 21150 kHz, 24930 kHz, and 28200 kHz.[6]
As part of an International Telecommunications Union-funded project, radio propagation beacons were installed by national authorities at Sveio, Norway (callsign LN2A, JO29po) and at Darwin, Australia (callsign VL8IPS, PH57pj). The beacons operated on frequencies 5471.5 kHz, 7871.5 kHz, 10408.5 kHz, 14396.5 kHz, and 20948.5 kHz.[7] Since 2002, there have been no reception reports for these beacons and the relevant ITU web pages have been removed.[8]
The Deutscher Amateur-Radio-Club sponsors two beacons which transmit from Scheggerott, near Kiel ( JO44vq).[9] These beacons are DRA5 on 5195 kHz and DK0WCY on 10144 kHz. In addition to identification and location, every 10 minutes these beacons transmit solar and geomagnetic bulletins. Transmissions are in Morse code for aural reception, RTTY and PSK31.[10] DK0WCY operates also a limited service beacon on 3579 kHz at 0720-0900 and 1600-1900 local time.
The Radio Society of Great Britain operates three radio propagation beacons on 5290 kHz, which transmit in sequence, for one minute each, every 15 minutes. The project includes GB3RAL near Didcot ( IO91in), GB3WES in Cumbria ( IO84qn) and GB3ORK in the Orkney Islands ( IO89ja). GB3RAL, which is located at the Rutherford-Appleton Laboratory, also transmits continuously on 28215 kHz and on a number of low VHF frequencies (40050, 50053, 60053 and 70053 kHz).[11]