το 1991 ηταν τόσο άγρια τα σποραδικά που ειναι πιθανόν να πήγε και μέσω σποραδικου. Τωρα για τροποσφαιρική δύσκολο αλλά όχι ακατόρθωτο, διότι μεσολαβεί θάλασσα.
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Συνδεθείτεαπο την Wikipedia:
Sporadic E usually affects the lower VHF band I (TV channels 2 – 6) and band II (88 – 108 MHz FM broadcast band). The typical expected distances are about 600 to 1,400 miles (970 to 2,300 km). However, under exceptional circumstances, a highly ionized Es cloud can propagate band I VHF signals down to approximately 350 miles (560 km). When short-skip Es reception occurs, i.e., under 500 miles (800 km) in band I, there is a greater possibility that the ionized Es cloud will be capable of reflecting a signal at a much higher frequency – i.e., a VHF band 3 channel – since a sharp reflection angle (short skip) favours low frequencies, a shallower reflection angle from the same ionized cloud will favour a higher frequency.
tropo:
Ducting can occur on a very large scale when a large mass of cold air is overrun by warm air. This is termed a temperature inversion, and the boundary between the two air masses may extend for 1,000 miles (1,600 km) or more along a stationary weather front.
Temperature inversions occur most frequently along coastal areas bordering large bodies of water. This is the result of natural onshore movement of cool, humid air shortly after sunset when the ground air cools more quickly than the upper air layers. The same action may take place in the morning when the rising sun warms the upper layers.
Even though tropospheric ducting has been occasionally observed down to 40 MHz, the signal levels are usually very weak. Higher frequencies above 90 MHz are generally more favourably propagated.
High mountainous areas and undulating terrain between the transmitter and receiver can form an effective barrier to tropospheric signals. Ideally, a relatively flat land path between the transmitter and receiver is ideal for tropospheric ducting. Sea paths also tend to produce superior results.
In certain parts of the world, notably the Mediterranean Sea and the Persian Gulf, tropospheric ducting conditions can become established for many months of the year to the extent that viewers regularly receive quality reception of signals over distances of 1,000 miles (1,600 km). Such conditions are normally optimum during very hot settled summer weather.
και αυτό απο ένα φόρουμ
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ΣυνδεθείτεRemember holidaying in Majorca in late 1980's and seeing rugby via BBC Wales in a bar there. Picture was a bit grainy but watchable all the same.
Αχ... ωραίοι καιροι τότε, όλα τα κανάλια ηταν ελευθερα και μπορούσες να κάνεις DX. Μα... γιά μισό λεπτό. Και τώρα στο Ηράκλειο τα πιό πολλά κανάλια ειναι ελευθερα, η ΕΡΤ εχει κλείσει, ειναι μέσα καλοκαιριου και όλη την ώρα ανοιγουν σποραδικά! θα μου επιτρέψετε να αποσυρθω, πάω να κατασκευάσω μιά VHF1 κεραία!
Θέμα: Τηλεοπτικό τοπίο ΝΟΜΟΥ ΑΤΤΙΚΗΣ (Αναγνώστηκε 164654 φορές)
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