#### Sporadic E (Es)

**Title:** Example of Sporadic E (Es) on 25 MHz from WWV

**Contributed by:** Gwyn Griffiths G3ZIL

**Reviewed by:**

**Receiving Station Location:** AC0G_B2 near Columbia, Missouri EM38ww

**Receiving Station Details** WSPRDaemon Grape SDR receiver.

**Feature Description**

![Sporadic_E_AC0G_B2](https://github.com/user-attachments/assets/5c90138e-77a2-4c16-b7b9-43ee20eebd1e)

Sporadic E (Es) is a propagation mode of interest to many radio amateurs, particularly at upper HF and VHF. It is also a propagation mode of interest to researchers. Christos Haldoupis, University of Crete, has written an excellent [tutorial review](https://users.physics.uoc.gr/~chald/christos/images/files/Publications/5.%20Review%20Papers-%20Book%20Contributions/RP5.pdf). One characteristic of Es is that it can enable propagation at times of the day when an upper HF band would normally be closed, e.g. during late evening at the path mid point. The above spectrogram is a good example. This 25 MHz trace on a 1112 km path from WWV to AC0G_B2, Missouri, on 16 June 2025 shows truly 'sporadic' band openings. The longest duration opening began ~0400 UTC and persisted for over two hours. That is, it began about 2100 local time at the path mid point: about 90 minutes after sunset. 

As ever, these spectrograms can pose a number of questions for further study. For example, while the 0400-0615 UTC opening has a mean Doppler of near zero the trace is quite wide. This suggests multipath propagation of some kind. Contrast the trace thickness in that interval to the brief very fine trace just before 2000 UTC.