Who this entry is for — Readers who need to distinguish the measured duration of an oscillation from its nominal label and from the displacement of turning points in price.
The cyclic period, or wavelength, is the time interval associated with one complete iteration of a component. In the Hurst/Hickson tradition, it is normally measured between two consecutive troughs of the same component.
It may be expressed in calendar time, sessions or bars, provided that the unit and the treatment of market closures are stated.
Three quantities not to confuse
| Term | Meaning |
|---|---|
| Nominal period | Reference label in the model |
| Observed wavelength | Estimated distance between two troughs of the same component |
| Variation | Change in wavelength and magnitude over time |
The original table in Profit Magic is not the modern “10–20–40–80 bar” progression. It includes durations from 18 years to 1.625 weeks, with ratios that are not always 2:1. The table and historical measurements appear in Hurst nominal cycles.
Extensions below five days and intraday grids belong to the later tradition, particularly Hickson/Sentient Trader; they must not be backdated to the 1970 book.
Variation is not time translation
A wavelength may shorten or lengthen: in the model's vocabulary, this is variation.
Time translation instead describes the displacement of turning points observed in price relative to the ideal turning points of the components, caused by their sum and the underlying trend. It is not a synonym for a period contracting or stretching.
How to report a measurement
A usable estimate should state:
- the component intended to be measured;
- the pair of troughs and the criterion used to identify them;
- the unit: calendar time, sessions or bars;
- the sample size and dispersion, not only the mean;
- the relationship to the nominal used as a reference;
- the method: envelope, phasing, filter or spectrum;
- the date of the latest recalibration.
Descriptive example — Three trough-to-trough intervals of 38, 41 and 39 bars have a mean of 39.3. Calling this a “40-bar cycle” is a summary of the sample, not proof that the next trough will arrive exactly 40 bars later.
An FLD for that component is constructed with an offset close to half the specified wavelength. The offset does not certify that the period is correct: it inherits the uncertainty in the estimate.
Sources
- J. M. Hurst, The Profit Magic of Stock Transaction Timing, Prentice-Hall, 1970, Ch. 2, Table II-1 and sections on nominality and variation.
- David Hickson, 10 Core Concepts of Hurst Cycles, concepts 1, 5, 6 and 10, Sentient Trader PDF.