Sporadic E is very useful form of radio propagation that is used by radio amateurs. It enables communications to be made, often at relatively high frequencies, when no other long distance mode of propagation might be available.
Sporadic E is used by radio hams on bands from about 24 or 28MHz up to 144 MHz and very occasionally 225 MHz in the USA. It is widely used on 28 and 50 MHz to yield long distance contact when no other forms of ionospheric propagation re available.
As the name indicates, it is sporadic by nature, but knowing the right times to look and knowing how best to operate can yield some good results,.
Sporadic E, also known as Es (i.e. E sporadic) is a form of E layer ionisation that occurs randomly in the ionosphere. It can affect frequencies normally affected by ionospheric propagation, but as the levels of ionisation can rise very high, it can affect frequencies much higher than would be expected by normal E region ionisation.
For radio hams, sporadic E offers the possibility of long distance communications, for commercial users, it gives rise to occasional very high levels of unwanted interference when signals that would not normally be heard are received over very long distances and at high strength.
Sporadic E basics
As the name indicates, sporadic E propagation occurs sporadically. It is difficult to predict, but there are times of the day and year when it is more likely to occur.
For the radio amateur, sporadic E offers many possibilities including that of ionospheric propagation on frequencies as high as 144 MHz. As sporadic E on these frequencies can be very short lived, the bands really liven up and operating is very exciting.
On bands with lower frequencies, sporadic E is longer lived and more frequent, and particularly in the periods of the sunspot minima, it offers ionospheric propagation when no other long distance options may be open for amateur radio.
More about Sporadic E:
Sporadic E arises when very intense clouds of ionisation build in the lower reaches of the E region of the ionosphere. The level of ionisation may be up to five times greater than those normally achieved at the peak of the sunspot cycle and this is the reason why signals well into the VHF region of the radio spectrum can be reflected. In view of the very high levels of ionisation, the levels of loss are particularly low.
Read more about Sporadic E propagation.
Predicting Sporadic E radio propagation
One of the key issues for radio hams with sporadic E is trying to pick times when it will occur. By knowing the most likely times for it to occur, it is possible to keep a listening ear open on possible amateur radio bands and frequencies.
Unfortunately, as the name suggests, the occurrence of sporadic E radio propagation is not easy to predict. However a large amount of statistical data has been collected and from this it is possible to judge the times when it is likely to occur.
In temperate regions, i.e. those in the mid latitudes between the equatorial regions and Polar Regions, sporadic E is found to occur mainly in summer. In the northern hemisphere the months of May to August yield the highest number of openings with a peak in June, and as a result it is found that the two Metre openings generally only occur in June and July. Surprisingly a small peak of sporadic E occurrences in general is also noticed in December, although these openings rarely affect the higher VHF bands. A similar pattern is also apparent in the equivalent months, November to February in the southern hemisphere.
The time of day also has a significant effect on sporadic E. There are two main peaks that occur. The first is around midday and there is another at around 7 pm. It is found that there are fewer occurrences in the afternoon and particularly in the morning. There are also very few at night.
The occurrence of sporadic E is rather different outside the temperate regions. In equatorial regions the occurrence of sporadic E is primarily a daytime phenomenon, and because of the proximity to the equator there is little difference the over the course of the year. In Polar Regions what is often termed Auroral sporadic E occurs and again there is little difference between the seasons but it is found that the ionisation for the sporadic E usually occurs in the morning.
One key to detecting he presence of a sporadic E opening on the higher frequency amateur radio bands is to use a VHF FM radio. Occasionally stations from far afield can be heard via sporadic E, and this should be a trigger to start monitoring the two metre amateur band for long distance signals.
How to use Sporadic E for ham radio contacts
The way in which sporadic E is used can determine the success of an event. Those who know how to use it to its best will be able to make the most of it. The actual techniques involved will depend upon the frequencies used.
- 50MHz and below: Sporadic E openings on the 50 MHz, 70 MHz (for those who have access to this band) and 28 MHz amateur radio bands tend to be similar to a normal E layer opening on that band. The sporadic E ionisation tends to affect these frequencies for much longer and therefore the operating techniques tend to follow those normally used for HF band contacts. It is sometimes best not to hold a contact for too long, as conditions can change relatively quickly.
- 144 MHz and above: Sporadic E openings on the 144 MHz amateur radio band tend to be infrequent and short lived. Activity tends to increase very rapidly as news of the opening spreads via the Internet, social media and various other means. Contest style contacts are normally made, with exchanges consisting of just the callsigns, locator and report. Additionally it is likely to be found that the area to which the opening exists will change as the Sporadic E clouds are blown about in the upper atmosphere. Radio amateurs who are operating should be prepared to change the headings of their antennas to follow the opening. Additionally some stations can fade away very quickly. When this happens, it is very unlikely they will e heard again.
It is also worth being aware that stations that can be heard in one area may be inaudible only 10 km away, so this creates opportunities for stations that may have lower power levels or poorer antennas.
When openings occur on the 144 MHz amateur radio band, speed is key to success using sporadic E for ham radio contacts. Make as many contacts as quickly as possible, because the it is likely that the opening could finish very quickly.
Using sporadic E for amateur radio operation requires different approaches dependent upon the frequency band in use. The higher the frequency, the shorter the opening is likely to be.
The rewards of operating on the VHF bands during a sporadic E opening can be very high. Accordingly it is worth monitoring band conditions as much as possible during periods when openings are possible. In this way it can be possible to make the most of any sporadic E openings that may occur and the maximum number of contacts with other radio amateurs can be made.
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