40MHz (8m) TEP propagation from the ZS6WAB CW beacon

 

40MHz (8m) TEP propagation from the ZS6WAB CW beacon

Why ZS6WAB matters

The ZS6WAB CW beacon is situated near Polokwane, South Africa in QRA locator KG46 and runs 30W to a 5 element yagi pointed north towards Europe on a nominal frequency of 40.675MHz. Its southern hemisphere location makes it ideally placed for studying transequatorial propagation (TEP) into Europe. More importantly, it appears to be the only consistently monitored beacon on this path.

The dataset analysed here spans 16 June 2022 to 16 March 2026 and comprises 2,502 reception reports submitted via DX Cluster and the UK Beaconspot archive.

TEP: a long-studied but still evolving mechanism

Transequatorial propagation is not new. It has been studied continuously since the late 1940s, with the first recognised observations dating back to around 1947. Despite decades of research, TEP remains an active area of investigation, with new refinements and theoretical developments still being proposed.

Modern understanding points to a complex interaction of equatorial ionisation structures, including plasma bubbles, ionospheric upwellings and large-scale wave dynamics. These mechanisms are not static, and the variability seen in amateur observations reflects that complexity.

This is important context: the ZS6WAB archive should be viewed not as an  explanation of TEP, but as an observational dataset contributing to an ongoing body of research.

Dataset overview

The archive contains:

  • 2,502 total spots
  • 1,581 explicitly labelled TEP
  • 210 explicitly labelled F2
  • Remaining entries unlabeled or minor categories

Only explicitly labelled entries are used for firm conclusions.

Table 1 – Explicit propagation labels

Mode  Spots
TEP  1581
F2  210
TR  44
ES  4

Interpretation:
TEP is the dominant labelled mode by a large margin. F2 is present but clearly secondary within this dataset and of course being a manually entered record it depends on interpretation by the monitoring station as to what the propagation mode actually was.

Seasonality: strong equinoctial dominance

The most striking feature is the seasonal distribution. TEP activity is heavily concentrated around the equinox periods.

Table 2 – TEP spots by month (all years combined)

MonthTEP Spots
Jan    86
Feb   320
Mar   379
Apr   178
May   16
Jun   5
Jul   2
Aug   8
Sep   94
Oct   344
Nov   111
Dec   38

Interpretation:

  • Clear peaks: Feb–Mar and Oct
  • Minimal activity: May–Aug
  • Pattern consistent across multiple years

This strongly supports a genuine TEP mechanism rather than sporadic or random propagation.

Year-on-year behaviour

The seasonal pattern repeats annually, but signal density varies significantly.

Table 3 – Annual TEP activity

YearTEP Spots  Active Days   Avg Spots/Day
2022   92     43        2.14
2023   224     103        2.17
2024   450     153        2.94
2025   573     154        3.72
2026*   242     59        4.10

*2026 partial year (Jan–mid March)

Interpretation:

  • Clear increase from 2022 - 2025/26
  • Pattern repeats, but intensity is not constant
  • Data is consistent with enhanced propagation during Solar Cycle 25 maximum

Important:
The dataset shows correlation with the solar maximum period, but does not prove direct causation for individual events.

Geographic footprint

The reception area is extensive across Europe.

Observed limits (TEP-labelled spots)

  • North: Faroe Islands (~10,060 km)
  • West: Ireland (~9,230 km)
  • East: Black Sea region (~7,600 km)

Table 4 – Main reception regions (by locator prefix)

Locator    SpotsRegion
JN    1228    Southern/Central Europe
JO    146    Northern/Central Europe
IO    121    UK & Ireland
KP    26    SE Europe
KN    11    Eastern Europe

Interpretation:

  • Strong concentration in southern/central Europe
  • Regular extension into UK and northern Europe
  • Occasional reach into far north and eastern regions

Note: This reflects both propagation and listener distribution.

Duration of TEP events

Because this is a CW beacon dataset, durations reflect observed activity, not exact opening/closing times.

From the data:

  • Median duration: ~0.8 hours
  • Upper quartile: ~2.2 hours
  • 95th percentile: ~4.6 hours
  • Maximum observed: ~9 hours

Interpretation:

  • Most events are relatively short-lived
  • Some extend significantly longer
  • True durations are likely underestimated

Time-of-day characteristics

TEP activity is concentrated around:

  • Late morning to early afternoon UTC
  • Peak around 10–12 UTC

This aligns with expected daylight ionisation conditions along the path.

Mixed-mode observations

The dataset shows:

  • ~27% of TEP days also include F2-labelled spots
  • Very limited explicit ES overlap

Interpretation:

  • Mixed-mode conditions do occur
  • However, the dataset does not allow reconstruction of propagation chains
  • No firm conclusions on Es + TEP coupling can be drawn from this file alone

Solar cycle influence

The strongest TEP activity occurs during:

  • 2024–2026 period
  • Corresponding to Solar Cycle 25 maximum phase

Interpretation (data-supported):

  • Increased solar activity likely enhances probability of 40MHz TEP
  • The dataset supports correlation
  • It does not isolate individual solar triggers

CW beacon vs WSPR: a practical comparison

The ZS6WAB beacon demonstrates that:

  • A simple CW system can produce a valuable long-term dataset
  • Manual spotting is sufficient to identify major trends

However, limitations are clear:

  • No continuous monitoring
  • Missed weak signals
  • Imprecise timing

Why WSPR would improve this work

A WSPR beacon would:

  • Capture true start and end times
  • Provide continuous 24/7 sampling
  • Detect weak and marginal propagation - WSPR is roughly 10dB more sensitive than CW
  • Allow deeper analysis of mode transitions

Final assessment

The ZS6WAB dataset provides strong observational evidence that:

  • 40MHz TEP between southern Africa and Europe is:
    • Real
    • Repeatable
    • Strongly seasonal
  • The pattern:
    • Peaks around equinoxes
    • Repeats annually
    • Intensifies during solar maximum
  • The path:
    • Extends across much of Europe
    • Is not limited to a narrow corridor
  • Typical events:
    • Are moderate in duration
    • Occur in daylight hours
  • A CW beacon:
    • Is scientifically useful
    • But could be significantly enhanced by WSPR

This article reflects a combination of traditional amateur radio experimentation and modern AI assisted analysis, where original data and direction are provided by the author and advanced tools enable deeper exploration and presentation of the results.

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