How to set up the radio so the decoder reads best
1. CW mode and a narrow filter
Listen in CW mode (not SSB) with a 250–500 Hz filter. The filter should hold one station — the one you want to read. Set the radio’s CW pitch to 500–700 Hz.
2. Why not SSB and a wide filter
In a wide filter (2–3 kHz) several stations are heard at once and the network does not know which to read. Our measurement on real recordings: when a second station of similar strength transmits nearby — even 250 Hz away — reading drops from 97% to 37% of words. A narrow filter in the radio or clicking the station on the waterfall (program filter) helps: then 88%.
3. AGC
Fast AGC on a strong station lowers the noise with every character — the noise “pumps” and upsets the rhythm of dots and dashes. Set AGC to medium or slow. With very strong signals it is better to switch on the attenuator or reduce RF GAIN than to overload the receiver.
4. Signal strength and audio level
Preamp only for weak signals. Set the sound card input level so the loudest station does not reach the maximum (no clipping) — the decoder copes with a quiet signal, not with a clipped one.
5. Two receivers
Radios with two receivers (MAIN / SUB) usually give two audio channels: left = MAIN, right = SUB. Choose the channel on the top bar (L / R) — then the decoder reads only one receiver.
6. Why one station at a time
The decoder reads the whole contact — hand keying, plain text and weak signals too. It works best when it hears one station: several stations in a wide filter mix into one text. In our test a second station of similar strength left 23–37% of the words, and after clicking the station — 88–90%. Hence a narrow CW filter in the radio or a click on the station in the waterfall.
7. Receive only
The program never transmits. It changes the frequency only when you click “Tune” (and enable it in the settings).
8. Several stations at once
The program reads up to 4 stations at the same time, each on its own channel (circles 1–4 on the waterfall) and in its own text pane. Left click — your station (1, main pane), right — the other party (2), Ctrl+click — 3 and 4 (Mac: ⌘); the program picks the rest. Example from a recording by SP4NKJ: next to a strong contest station PA3AAV, 5–8 dB weaker, DK2DR was in a QSO with IU3USO. One decoder for the whole passband showed only the contest; a separate channel — the whole QSO: “TNX FER FB QSO … ALL THE BEST FER U AND FAMILIE 73”.
Channel circles on the waterfall
- Left click — 1 (your station, main pane), right — 2 (the other party), Ctrl+left — 3, Ctrl+right — 4 (Mac: ⌘).
- Same number — filled circle (your choice) ↔ empty (the program picks); another number — swap.
- Drag the circle: sideways — another tone, onto another circle — swap, off the waterfall — remove (Esc — cancel).
- Right click — this station to channel 1 (main pane); the station from 1 moves here.
The same text is in the program: the “How to use the radio” button.