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Decoding WSPR

WSPR ("whisper") is a beacon mode for seeing where a band is open. Stations send their callsign, grid square and power, very slowly and very narrow, so they can be decoded far below the noise. The console's WSPR panel lists the beacons your radio hears. The RemoteMyShack agent decodes them at the shack, by the shack computer's clock, so it works on a slow connection and with your device's audio off.

WSPR is part of the Super Station plan (and the free trial) when you operate remotely. At the shack, on the shack computer's own network, it's always available. See Plans and pricing.

Open the panel

Put the radio in USB with DATA on (USB-D). A panel for digital modes opens under the mode buttons.
Click WSPR in the row of buttons above it.
Choose a band from Go to band…. It tunes to the band's WSPR frequency (14.0956 MHz on 20m) and switches to USB-D if the radio isn't in it.

Each WSPR transmission starts a second into an even minute and lasts nearly two minutes. The beacons heard in it appear just before the next even minute. The progress bar shows where the current two-minute slot is.

The agent decodes only while at least one console has the WSPR panel open. When you open it, it shows the last half hour it decoded, if anyone had it open.

Reading it

Newest first, one line per beacon:

UTC: when the slot started (hhmm).
dB: the signal-to-noise ratio in 2500 Hz, an estimate. On a busy band it reads a few dB lower than WSJT-X. WSPR decodes down to about -28 dB.
DT: how many seconds late the transmission started.
MHz: the beacon's frequency.
Drift: how many hertz the signal moved over the transmission.
Call, Grid and dBm: what the beacon sent. 37 dBm is 5 W, 30 dBm is 1 W, 23 dBm is 200 mW.
km: how far away it is, from the middle of your grid square to the middle of theirs. It needs your station's grid, which you set on the FT8 panel.

A beacon with a compound callsign (such as PJ4/K1ABC) is shown without a grid. One sending a six-character grid sends a code for its callsign instead of the call itself: the panel shows the call in angle brackets, such as <PJ4/K1ABC>, once it has heard that station's own beacon, and <...> until then.

Clear empties the list in this console.

Tips

Keep the radio's receive filter wide enough for 1400 to 1600 Hz of audio, where WSPR beacons are, and its noise reduction off.
The shack computer's clock must be right to within about a second, as for FT8.

How it decodes

The decoder is built from the published WSPR protocol. In tests it decodes signals down to about -29 dB, close to WSJT-X. On a busy band it finds about three quarters of what WSJT-X does: it misses some beacons right on top of a stronger one, and ones that start more than 2.5 seconds late.

Not built yet: sending what you hear to WSPRnet, and transmitting WSPR.