The signal chain,
end to end.
A desktop engineering suite for software-defined radio work — synthesize modulated waveforms, recover the bits blind, and dissect the resulting bitstream, with a console that shows its math at every step.
Synthesize the signal you need.
Pick a scheme, shape the pulse, chain the coding — Belle renders the constellation and spectrum before a single sample hits disk.
[gen] qpsk @ 250 ksym/s · rrc α=0.35 · span 8
[gen] fec: conv k=7 r=1/2 · xor randomizer
[ok] wrote burst_qpsk_250k.cf32 (2.4 MB)
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13 schemes, one dialog
BPSK through 64-QAM, FSK and MSK — with per-scheme symbol mapping you can edit by hand.
Pulse shaping done right
Root-raised-cosine filtering with configurable roll-off, previewed in the spectrum before export.
Coding chains
Convolutional FEC, scramblers, and randomizers stack in the order real waveforms use them.
Recover bits you didn't transmit.
Costas carrier recovery and Gardner timing pull the constellation into lock, while the LFSR analyzer identifies the scrambler that's hiding the data.
| Deg | Polynomial | Period | Type | Score |
|---|---|---|---|---|
| 15 | x¹⁵ + x¹⁴ + 1 | 32 767 | Fibonacci | 98.7 |
| 7 | x⁷ + x⁶ + 1 | 127 | Galois | 41.2 |
| 9 | x⁹ + x⁵ + 1 | 511 | Fibonacci | 22.8 |
Blind lock
Costas + Gardner loops converge without a training sequence — watch the clusters tighten live.
Honest metrics
Bits, symbols, and EVM update as the loop settles, so you know the demod is real, not lucky.
Scrambler cracking
The LFSR analyzer sweeps candidate polynomials and scores them by period match and entropy drop.
See the structure inside the bits.
A visual bit-raster with chainable worksheet operations — descramble, deinterleave, frame-sync — and a shelf of analysis spies for whatever's left.
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Worksheets, not scripts
28 bit operations — invert, deinterleave, derandomize, Viterbi, Reed-Solomon — chained visually per tab.
Sync jumps out
Solid columns in the raster are frame alignment made visible; the viewer finds the width for you.
13 analysis spies
Dockable panels for bit statistics, telecode, RS detection, audio playback, and LFSR tap search.
One suite, four tools.
13 modulation schemes
BPSK, π/2-BPSK, QPSK, π/4-QPSK, OQPSK, 8-PSK, QAM to 64, FSK, and MSK — generated or demodulated.
Blind demodulation
Costas carrier recovery and Gardner timing with a live constellation and EVM readout across all schemes.
LFSR recovery
Automatic scrambler polynomial identification with period, entropy-drop, and confidence scoring.
FEC lab
Viterbi decoding of K=7 convolutional codes, punctured rates, and Reed-Solomon (255,223).
Bitstream workbench
28 chained bit operations and 13 dockable analysis spies over a dual-view synchronized raster.
Waveform viewer
Time domain, spectrogram, power spectrum, I/Q scatter, and time-raster displays with a full marker toolkit.