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What to listen to · Fax and digital signals

MSK144 on 144.360 MHz: meteor scatter pings on 2 metres

On 144.360 MHz European stations bounce short bursts off the ionised trails of meteors, waiting for a ping. ShackDeck decodes the pings and puts the stations on the map; best before dawn and in the big showers.

Frequency144.360 MHz
ModeMSK144

What you hear

Mostly nothing, and then something. The frequency is silent for most of the time, and then a ping arrives: a sudden burst of hiss, a tenth of a second to a second long, sometimes a longer burst of several seconds that rises and falls. That is the signal of a station hundreds of kilometres beyond the horizon, reflected off the trail of a meteor that burned up eighty to a hundred kilometres up. The trail lives for a moment and the signal lives with it. On the waterfall a ping is a wide, short flash across the whole passband, because the signal is 2400 Hz wide and the decoder needs the whole of it.

The transmitting station repeats one short message continuously for its whole 15-second period, in frames of 72 milliseconds, so that any ping long enough to contain one frame can be decoded. The messages are the ones FT8 uses: a CQ with a callsign and a grid, two callsigns and a report, R and the report, RR73, 73, with the shorthand of meteor scatter where everyone knows the custom. A contact can take ten minutes of patience and arrive in four pings.

Who transmits and why

VHF amateurs, who have worked over meteor trails since the 1950s, first with fast Morse played from tape, then with the computer modes of the WSJT project. MSK144 was released in 2016 and replaced its predecessors because it decodes a whole message from a single ping. The Earth collects meteors all day, every day, so sporadic pings happen at any hour, and the distances, from about 500 to 2300 kilometres, make a 2 metre contact possible between countries that never hear each other otherwise. 144.360 MHz is the agreed European calling frequency for the mode: stations call here and move to a working frequency once they have found each other.

When and where to listen

The best hours are before dawn and in the early morning, local time, when your side of the Earth faces the direction of its travel and sweeps up more meteors; the evening is the poorest. The great days are the showers: the Quadrantids at the start of January, the Perseids around 12 August, the Orionids on 21 and 22 October, the Leonids in mid-November and the Geminids on 13 and 14 December, when the frequency carries pings every few seconds and stations stay on for whole nights. The receiver has to have the 2 metre band, which rules out most public receivers; one with a horizontal antenna in the open hears more than a vertical in a city. The 15-second periods are timed by UTC, so the computer that decodes needs an accurate clock.

In ShackDeck

Station catalogue → Fax and digital signals → MSK144 144.360 (meteor scatter). The program picks a public receiver with 2 metres, tunes it to 144.360 MHz in USB and sets the MSK144 mode; no receiver, antenna or account of your own is needed. Each decoded ping appears in the decode list with its time, signal level and message, and the station lands on the map in its grid square with its flag, as FT8 stations do, with the bearing and distance from your own station. Long gaps between decodes are the normal state of this frequency, not a fault; leave it running through a morning, and during a shower leave it running all night.

More stations

SO-50: the FM repeater satellite on 436.795 MHz

436.795 MHz · FM

SaudiSat 1C, known as SO-50, carries an FM repeater that amateurs work with handheld radios: up on 145.850 MHz, down on 436.795 MHz. ShackDeck picks a receiver under the satellite's footprint.

APRS on 144.390 MHz: the North American frequency

144.390 MHz · APRS

The same packet network as on 144.800 MHz in Europe, on the frequency used across the United States and Canada. ShackDeck takes a receiver in the USA and puts the cars, weather stations and digipeaters on the map.

RS-44: the CW beacon on 435.605 MHz and the linear transponder beside it

435.605 MHz · CW

RS-44, also called DOSAAF-85, flies about 1200 km up with a Morse telemetry beacon on 435.605 MHz and an SSB transponder on 435.610 to 435.670 MHz. ShackDeck picks a receiver under the pass.

APRS on 144.800 MHz in Europe: cars, weather stations and digipeaters on the map

144.800 MHz · APRS

On 144.800 MHz European amateur stations send short packets with their position, weather and messages: cars on the move, home weather stations, digipeaters on hills. ShackDeck decodes them and puts everything on the map.

The Pip at night: the same marker on 3756 kHz

3756 kHz · USB

After sunset in Rostov the Pip leaves 5448 kHz and the same one-second pip goes out on 3756 kHz, where it reaches most of Europe. The night entry of the Russian channel marker.

CB channel 19, 27.185 MHz: truckers, AM and summer skip

27185 kHz · AM

Citizens band is radio without a licence, and channel 19 at 27.185 MHz is its road channel: drivers in AM a few kilometres apart on an ordinary day, and in summer, when the skip is in, voices from 2000 km away.