How to Set ALC for FT8 (Clean, Undistorted Signal)

Getting your ALC set correctly for FT8 is one of the most important steps in making sure your digital signal is clean, efficient, and easy for other stations to decode. Yet it’s also one of the most misunderstood parts of FT8 setup. Many operators either ignore ALC completely or assume that “a bit of ALC is fine,” when in reality, incorrect ALC levels can cause distortion, splatter, and reduced performance on the bands.

In this post, I’ll walk you through the proper way to set ALC for FT8, explain what ALC actually does, and show you how to check that your signal is clean. I’ve also embedded a full video tutorial below so you can follow along step‑by‑step.

How to Set ALC for FT8 on Yaesu Radios

What ALC Actually Does
ALC (Automatic Level Control) is designed to protect your radio from being overdriven. When the input audio level is too high, the radio reduces the gain to prevent distortion. That sounds helpful, but for digital modes like FT8, ALC intervention is something you want to avoid. When ALC kicks in, it changes the shape of your transmitted waveform, which leads to distortion and makes your signal harder to decode.
In short: ALC is a safety net, not a tuning tool. For FT8, the goal is to keep ALC as close to zero as possible.

The Correct FT8 ALC Level
The proper FT8 ALC level is simple: none, or as close to none as your radio allows. Different radios display ALC differently, but the principle is the same across all brands. You want to adjust your audio chain so that your radio is producing full, clean power without ALC intervention.
This usually means: • Setting your WSJT‑X output level to a sensible starting point • Adjusting your radio’s input gain or USB audio level • Watching the ALC meter as you transmit a test tone or CQ • Reducing audio until the ALC meter barely moves (or doesn’t move at all) If your ALC meter is climbing halfway or more, your signal is almost certainly being distorted.

An Example of Poor ALC for FT8

How to Adjust Your Audio for FT8
Start by setting your radio to the power level you intend to use. Then, with WSJT‑X transmitting a test signal, slowly reduce the audio level until the ALC meter drops to the lowest possible point. You should still be producing full RF output — the radio will happily deliver its rated power without ALC intervention as long as the audio is clean. If you find that reducing audio also reduces RF output, increase the radio’s internal digital gain or USB input level slightly, then repeat the process. The goal is a clean signal at full power with minimal ALC movement.

Checking Your Signal
Once you’ve set your ALC correctly, it’s worth checking your signal on a remote SDR or asking another operator for a quick report. A clean FT8 signal should appear narrow, stable, and free from splatter on the waterfall.

73's Mark