Friday, April 23, 2010

Detecting Sporadic-E on 2m

We are entering the Sporadic-E season, the favourite time of the year for those who enjoy operating the VHF bands. As Roger G3XBM suggested today, more stations this year will be using WSPR on the 10m and 6m bands, so many openings may be detected that would otherwise be missed. I am WSPRing on 10m at the moment, and will probably move up to 6m later on once 10m starts opening on a regular basis.

However, my first love will always be 2m. From this QTH surrounded by hills Sporadic-E is the only type of propagation that allows me to work DX on that band. On 2m, Sporadic-E openings are much rarer because much smaller patches of the Sporadic-E clouds are dense enough to reflect signals at this frequency. This makes propagation between two points on 2m much more fleeting. A station can be 59+ one minute and gone the next, which makes it essential to keep QSOs short and sweet: report, locator, and name only if you are sure you have got the time.

Some people are planning to use WSPR on 2m as well, but because of the fleeting nature of propagation I am not convinced that the 2 minute periods of WSPR make it the most appropriate method of detecting propagation on this band. I think it might be more fruitful to monitor 144.8MHz which is the APRS frequency in Europe.

APRS packets take only a second or two to send, so you don't need propagation to be good for two whole minutes to receive one. Packets do need to be received clearly, but the "strong or gone" nature of Sporadic-E on 2m suits that quite well. The main difficulty is knowing the location of the station that sent the packet you heard, since it could well be a digipeater retransmitting a packet sent from somewhere else.

There used to be a website that displayed a propagation map based on APRS packets received. But in the last few days it appears to have gone QRT, which is rather a shame. But if you are in a location that doesn't normally hear much APRS activity, even just hearing a number of signals going "braaap" on 144.8MHz could be the alert you need that some unusual propagation is about.

If anyone has any other ideas on how to improve the detection of Sporadic-E on 2m without sitting in front of the receiver listening to band noise for hours on end I'd be interested to hear them. If you aren't familiar with this mode of propagation and how it works and would like to learn more about it then there is an article about Sporadic-E on my website.
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