What this page measures
This page analyses the
reported receive frequencies of decodes from the
PSKReporter “Live” feed for
M7SQI. Before the time-window statistics
are calculated, the reported frequencies are normalised to reduce offsets caused
by different receivers and by separate transmit-frequency populations.
Frequency normalisation
Reports are first separated by receiver, band and mode. Within each of those
groups, distinct frequency populations are identified from gaps in the observed
frequencies. Each report is then expressed relative to the median of its own
frequency population.
This means that, for example, a receiver which normally reports one population
several hundred hertz away from another receiver does not create an apparent
several-hundred-hertz frequency shift simply because the reporting population
changes. Separate FT8/FT4 transmit-frequency populations are treated in the same
way rather than being mistaken for propagation-induced movement.
The current population separator uses gaps greater than 15 Hz.
Populations are retained and re-referenced independently; they are not discarded
merely because their raw frequencies are far apart.
Window statistics
The normalised reports are grouped into short time windows
(default
15 s). For each window:
- IQR (Hz) — interquartile range of the normalised frequency residuals.
- Δ median (Hz) — median normalised residual for the window, centred on the selected period.
- n/window — number of decodes contributing to that window.
How to read it
Low IQR indicates that the normalised reports agree closely within that window.
A larger IQR indicates greater spread within the active receiver/frequency
populations. Movement in Δ median shows a change in the centre of the
normalised reporting distribution.
These residuals may contain propagation-related frequency behaviour, but they
are not direct Doppler measurements. Receiver calibration,
reporting resolution, transmit-frequency choice and changing propagation paths
can all contribute to the remaining structure.
WSPR versus FT8/FT4
Fixed-frequency WSPR operation provides the cleanest case because the transmitted
frequency is effectively held constant. FT8 and FT4 are a more movable feast:
the transmitted audio position can change between transmissions. The population
normalisation is therefore particularly important for FT8/FT4, and small
residual excursions in those modes should be interpreted more cautiously.
Omnidirectional viewpoint
This is not a single fixed raypath. M7SQI illuminates many directions
simultaneously, and the aether decides who hears it. The plotted statistics
therefore represent a population-weighted view of the active paths at that time,
rather than one chosen great-circle path.
Space-weather context
Kp, GOES X-ray flux and solar-wind magnetic-field data are shown as environmental
context. Correlations and lag values are exploratory comparisons only. Agreement
in timing may be interesting, but does not by itself demonstrate that the
frequency residuals were caused by solar or geomagnetic activity.