---
name: "fst4sim"
section: "1"
platform: "linux"
package: "wsjtx"
version: "2.7.0+repack-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/fst4sim"
---

# fst4sim(1)

Generate simulated QRA64, FST4, and FST4W mode signals.

## NAME

fst4sim, qra64sim - Generate simulated QRA64, FST4, and FST4W mode signals.

## SYNOPSIS

**qra64sim** msg A-E Nsigs fDop DT Nfiles SNR

**fst4sim** msg TRsec f0 DT h fDop del Nfiles SNR W

## DESCRIPTION

**fst4sim** can be used to generate FST4 and FST4W signals with user-specified message content, mode parameters, and SNR values.

## ARGS

**msg**

A valid QRA64, FST4, or FST4W message enclosed in quotation marks.

**A-E**

QRA64 sub-mode designator.

**Nsigs**

Number of signals to simulate, distributed even across a 2000 Hz bandwidth.

**TRsec**

A valid T/R period duration (s).

**f0**

Integer signal frequency offset (Hz).

**DT**

Decimal signal time offset (s).

**h**

A valid modulation index.

**fDop**

Decimal Doppler frequency spread (Hz).

**del**

Decimal Watterson model delay (ms).

**nfiles**

Number of files to generate.

**snr**

Add Gaussian noise to simulate SNR in 2500 Hz bandwidth.

**W**

Hint to break ties between ambiguous messages *0* as 77-bit (FST4), *1* as 50-bit (FST4W).

Generated files are 12000 Hz sample rate, 16-bit unsigned format, mono PCM .WAV files suitable for replay using WSJT-X either vie the GUI [**wsjtx**(1)](/wsjtx/1.md) or using the command line slow mode decoder [**jt9**(1)](/jt9/1.md). Files are named 000000\_nnnnnn.wav (000000\_nnnn.wav for QRA64), where *nnnnnn* or *nnnn* increments from zero.

## AUTHOR

Joe Taylor, K1JT.

## COPYING

**fcal** is Copyright © 2001 - 2019 by Joseph H. Taylor, Jr., K1JT, with contributions from additional authors. WSJT-X is Open Source software, licensed under the GNU General Public License (GPLv3).

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.