|3. Operating Procedures|
So, you've set up your station and you are ready to go on the air. If you've worked HF before you will appreciate that the stations you will work is determined by many parameters including sunspot cycle, time of day, year etc. To be an effective DXer (particularly from a small garden) you need to be thoroughly familiar with all of these parameters. Let's take a brief look at some of them:
a) State of Sunspot cycle - HF Dxing relies heavily on ionisation in the upper atmosphere which in turn is affected by the amount of ionising radiation coming from the sun. Signals are reflected from ionised layers of particles in the upper atmosphere back to earth. High levels of ionisation result in better propagation and allow the use of higher frequencies for long distance communication. The amount of radiation reaching the earth is closely linked with the number of sunspots appearing on the surface of the sun, and it has been determined that sunspot numbers increase and decline in 11 year cycles. At the peak of a sunspot cycle worldwide communication will be possible on all the HF bands including 12 and 10 meters and quite often 6 meters as well.
At the bottom of a sunspot cycle the upper HF bands will basically shut down and most worldwide communication will occur on the lower bands (160, 80, 40 meters, and some openings on 30 and 20 meters).
A guide to the state of propagation can be gauged from the SFI (solar flux index) which can be found on DXclusters on packet radio and the internet, and also in ham radio news bulletins etc. As a rough guide the higher the SFI the better the propagation. At the bottom of the sunspot cycle SFI's will be around the 100 mark. Recently as we approach the peak of the latest cycle, SFI's over 200 have been recorded. So in summary, during sunspot maxima concentrate on the higher bands (particularly 10 meters), and during minima seek DX on the lower bands.
(b) Time of day - Choice of operating frequency is influenced heavily by time of day. Generally speaking 160,80 and 40 meters are regarded as night time bands because during daylight these frequencies tend to be heavily absorbed by the D layer in the upper atmosphere so that signals do not return to earth (although short skip over 1000 miles or so is often worked on 40m during the day). During hours of darkness the D layer disappears and these bands are reflected from the higher F2 layer back to earth providing worldwide communication (generally speaking the low bands tend to be noisier than the higher bands). The higher HF bands tend to shut down after dark and are generally thought of as day time bands, because the F2 layer from which they are reflected, thins out at night. During sunspot maxima however, the F2 layer can be so heavily ionised that even 10 meters can remain open all night.
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