Donchian channels: the simplest breakout envelope

Donchian channels draw the highest high and the lowest low of a window. Cross the upper line and you're in a multi-day high; cross the lower and you're in a multi-day low.

The famous turtle setup

Richard Dennis taught his "Turtle Traders" to enter on Donchian 20-day breakouts and exit on a 10-day Donchian against them. The system was mechanical, the same rules applied to every market, and it made fortunes in trending markets in the 1980s.

The premise is simple: if an asset has broken to a new 20-day high, the trend that produced that high is likely continuing. You stop being right when price prints a 10-day low against you.

Why it still works (and when it fails)

The asymmetric payoff — small losses on whipsaws, large gains on trends that run — survives because trends in markets persist longer than random-walk theory predicts. The cost is many small losing breakouts before a real trend appears.

Failure mode: range-bound markets eat Donchian breakouts for breakfast. Every breakout retraces. The Turtle system spent the late 1990s losing money until trends returned.

How Signodex uses Donchian

Signodex renders 20-day Donchian channels on stocks, ETFs and crypto. The AI references the position in the channel ("Price has touched the upper Donchian for the third session — the prior two failed to follow through, raising the bar for breakout confirmation") without directing the entry.