[SADXA] Anatomy of a Sporadic E Event

[W7EXG (Bill)]

To: SADXA 
>From Bill W7EXG
RE: Anatomy of a Sporadic E event

Some of you may know we had a significant sporadic E event this morning of
June 18 from 1615z to 1830z 

I call the event significant when the vertical reflection from the sporadic
E layer prevents little to no access to the upper F1 and F2 layers. Thus ALL
band propagation is by the Sporadic E layer.  

When this occurs, it is referred to as a "Blocking" event. 

The data below is a brief summary of the foEs data from the Austin Ionogram
Web site this morning.  

As a quick Primer: 

foEs is the Critical Frequency of the sporadic E layer. 

The critical frequency is determined by vertical RF sounding, where RF
reflection occurs back to ground for frequencies less than foEs.  

The Maximum Usable Frequency of the Sporadic E layer (EsMUF) = M x foEs.

The M factor is defined by the altitude of the Sporadic E layer. Typically,
for low elevation angles, an approximate M factor for Sporadic E is about 6.


SUMMARY of the EVENT AT THE AUSTION SITE

6/17/19
TIME(z) foES(MHz) EsMUF (MHz)
1630z - 4.0		24
1645  - 6.8		40.8
1650 	- 9.7		58.2
1700 -  9.9		59.4
1710 -  12.8	76.8 Highest Peak
1715 -  9.7		58.2	
1725	-  9.6	57.6
1740  - 9.8		58.8
1745  - 9.69	58.1
1750  - 8.5		51
1800 -  6.96	41.78
1815 -  3.7		22.2

NOTE: This was about a 1 hour event. SHORT!! 
Blocking and 6m activity occurred from about 1650z to 1750z. 
10m activity was from about 1645z to 1800z.  I personally made many 10m
contacts at that time, one was with a W3. 

One unique aspect of Sporadic E blocking is that the lower frequencies
cannot penetrate the Es Layer either, and their signals too reflect off the
same Sporadic E layer. 

Several Stations on 10m reported that they took a 10m station down to 12m,
15m, and 20m and had good signals between the two stations on all 4 bands.
This is to be expected and is the reason for very short skips on all bands
during this event. All band signals are reflecting off about the same 95Km
Sporadic E Height. 

This is some food for thought for you Sporadic E lovers. 

MORE FUN TO COME THIS SUMMER!

73's, 

Bill W7EXG