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

What you hear

On 435.605 MHz a steady Morse signal that never stops: the beacon sends the satellite's name and then its telemetry, numbers for voltages, currents and temperatures, over and over, at a comfortable speed. The pitch tells you the pass is real: with the Doppler shift on 70 centimetres the tone glides slowly downwards across the whole pass, about 10 kHz from rise to set, so a receiver left on one frequency hears the beacon walk through its passband and out the other side. On the waterfall it is a bright line sloping gently from upper left to lower right, the signature of every satellite beacon.

Just above it, from 435.610 to 435.670 MHz, is the transponder passband, and this is where the people are: SSB voices and Morse from stations all over the footprint, half of Europe at once on a good pass, each signal drifting with the same Doppler. The contacts are unhurried, callsign, report, grid square, town, a few words about the antenna, because a pass lasts long enough for conversation. The transponder is inverting: stations transmit in lower sideband on 145.935 to 145.995 MHz, and the satellite turns it into upper sideband on the way down.

Who transmits and why

RS-44 was built in Russia and named DOSAAF-85 for the 85th anniversary of the volunteer defence society that trained generations of Soviet radio amateurs. It was launched on 26 December 2019 with a group of communication satellites, and it stayed attached to the Breeze-KM upper stage that carried it, which is why orbit catalogues list the pair as one object. The payload is a classic linear transponder 60 kHz wide, which lets many stations share the satellite at once, each on its own frequency, plus the CW beacon that says the satellite is alive. Among the amateur satellites flying today it is one of the best for SSB, strong and nearly always on.

When and where to listen

The orbit is the reason to seek it out. At about 1200 kilometres RS-44 flies three times higher than the ISS, so its passes last twenty to thirty minutes and its footprint is nearly 4000 kilometres across: a receiver anywhere in Europe hears it while it is over Europe, and five to eight passes a day are usual. The signal is strong enough for a vertical antenna; what matters is a receiver with 70 centimetres inside the footprint. The Doppler drift is slower than on a low satellite, so the SSB transponder is easier to follow by hand, but you still retune every few seconds; the beacon is the easiest thing to find first, around 435.600 to 435.615 MHz.

In ShackDeck

Station catalogue → Fax and digital signals → RS-44: the satellite beacon. When you click, the program asks where the satellite is at that moment, looks for a public receiver with 70 centimetres inside its footprint, takes the nearest one, tunes it to 435.605 MHz in CW and tells you which receiver the satellite is over; no receiver, antenna or account of your own is needed. If the satellite is out of reach of every receiver, the program says where it is and when the next pass over your own location begins, from the locator in the settings. Once the beacon is in the passband, turn the knob up into 435.610 to 435.670 MHz and switch to USB to hear the transponder. The Satellites tab shows the satellite's track and footprint on the map, the passes of the next 24 hours, a sky plot, and the transmitters with the Doppler-corrected downlink next to a Listen link, with a bell that reminds you ten minutes before a pass.