Tag: Beacon

PI4 next generation VHF/UHF beacons?

Beacons have like other digital modes moved with the times, making use of the latest digital modulation techniques to improve detectability far beyond the human ear and CW.

The name PI4- PharusIgnis4 comes from the ancient words for a beacon, lighthouse and fire and is a digital modulation that is compliant with the IARU Region 1 VHF Committee accepted 1 minute mixed mode beacon sequence.

The sequence of events is illustrated below, and always starts on a full 1-minute cycle.0 to 24 seconds PI callsign


25 sends CW ident callsign and locator


carrier until 59.5 seconds


To decode the PI4 beacons you can download software PI-RX by Poul-Erik OZ1CKG or MSHV by Christo LZ2HV, they both report being compatible with Linux and Windows.

OZ7IGY beacons date back to 1957, and they are now QRV from 28 MHz to 24 GHz. You can review the dial frequencies and check the operational status online.

Frequency [MHz] USB dial* ERP [W] ASL [m] 99% accuracy [mHz] Year QRV
28,271 28.270.200 10 95 1 2009
40,071 40.070.200 10 97 1 2007
50,471 50.470.200 25 98 1 1990
70,021 70.020.200 25 100 1 2003
144,471 144.470.200 50 102 3 1957
432,471 432.470.200 75 103 9 1958
1 296,930 1.296.929.200 90 95 26 1978
2 320,930 2.320.929.200 30 98 46 1985
3 400,930 3.400.929.200 50 96 68 2006
5 760,930 5.760.929.200 50 98 115 1992
10 368,930 10.368.929.200 80 97 237 1999
24 048,930 24.048.929.200 20 97 481 2012

To support the PI4 beacon project, or to see a technical description of the modulation technique read more on their website.

Other becons to look out for.

PI4 + CW + carrier/Next Generation Beacons platforms
4O0BCG in JP92PK – 70,048 MHz
DB0HRF in JO40FF – 144,475 MHz
DB0IH in JN39HJ – 432,447 MHz
DB0JG in JO31HS – 432,412 MHz
DB0LTG in JO31TB – 1296,7435 MHz
DB0MMO in JN49RV – 144,455 MHz and 432,425 MHz
EI0SIX in IO63VE – 50,005 MHz, SBP 5/0
GB3CFG in IO74CR – 70,027 MHz and 1296,905 MHz
GB3MCB in IO70OJ – 50,443 MHz and 50,005 MHz SBP 5/1 and 3
GB3MHZ in JO02PB – 10 368,830 MHz
GB3UHF in JO01EH – 432,430 MHz
IW9GDC/B in JM78SD – 50,006 MHz (Later SBP 6/4)
KG4BYN in EM75RV – 28,2368 MHz
ON0EME in JO21JG – 10 368,875 MHz and 24 048,875 MHz
ON0SNW in JO21BE – 10 368,965 MHz
OX4M and OX6M in HQ90AL – 70,047 MHz and 50,047 MHz
OZ4BHM in JO75KB – 50,005 MHz, SBP 5/4, later also 50,466 MHz
OZ7IGY in JO55WM – 28 MHz to 24 GHz
PA0AG in JO32GH – 70,095 MHz (personal beacon, 07-21 UTC)
SK4MPI in JP70NJ – 144,412 MHz
TF1VHF in HP94AC – 50,457 MHz
UA1ZFG/B in KP69AK – 144,425 MHz
VA2NQ in FN35NL – 50,295 MHz, 144,491 MHz, 222,295 MHz and 432,302 MHz

Receiving Non Directional Beacons (NDB)

NDB are low power beacons in the 250 to 550 KHz range. The beacons are usually situated at a landing strip/airfield / oil platform to aid navigation. They are non-directional so use a vertical omnidirectional antenna, and reasonably low power. The ERP is very low, as the physical size of the antenna restricts the efficiency and the desired range is usually not more than a few tens of miles.

Photo credit Original uploader (and claimed/alleged photographer) was Mintaka10.

The beacons transmit in double sideband AM, so you can often see the carrier AM frequency and then on both the upper and lower side of the carrier the CW ident. The CW consists of one, two or three letters, and the morse ident is unique so can be used to geolocate the beacon.

Wikipedia contains further information on how these are used by pilots to navigate, although most shortwave listeners are simply interested in identifying the signals and working out their location. The frequencies used to lend itself to some considerable distances at night, although its often the noise floor of the local area in this bands that limits the receiver. I found my doublet antenna was poor to useless at these frequencies, and it was the Wellbrook Loop that provided a significant improvement on this and other LF, MW bands. George M1GEO has also provided some details of a homebrew version of the loop, and details can be found on his site.

If you don’t have a suitable HF receiver and aerial a good way to start is by utilising one of the online SDR receivers.  Some have a text above the receiver window showing the name/location of any beacons received. You can often click on this text and the receiver will set the correct frequency and mode.

Keep in mind that local conditions and time of day will as it does on other HF bands influence the stations that can be received at any time.

The expanded version shows just one NDB, located at Epsom and using the CW ident EPM. The AM carrier can be seen in the center, with the morse ident either side. Its helpful to be able to look up any decoded and confirm the location, the simple ident EPM does not provide you with much of a clue to its location. I found Sean G4UCJ website very helpful as it contained a list of his received beacons.

On occasions, the received signal is very weak, and local noise can often obscure the signal. In some circumstances, it can be helpful to use software to enhance the signal. The software is often used in QRSS very slow/low power CW, and works be building up a number of samples of the signal as we know the same information is repeated time and time again.

NDB finder is another excellent choice for finding the hard to detect signals, you can try that for free for 21 days.

If you like exploring the HF bands below 500 kHz the world of NDB can provide some interesting conditions. If you enjoy NDB or you want to share any further information please get in touch.