Bogdan wrote: > > I have a question for those of you specialists on the propagation of radio waves. How far from the tx-site, a SW signal can reach without being reflected by the ionosphere thousands of kilometers away or so ? <<
I don't know the precise answers to this, which will, in any case, depend on Tx power and frequency. But in thinking about this, it's worth making the distinction between groundwave and skywave. SW broadcast transmissions intended for ionospheric propagation are almost always horizontally polarised, and are transmitted, from horizontal dipole arrays, without launching any vertically polarised *groundwaves* along the fuzzy boundary between ground and air. The HP wave will become tilted when it hits the ground, giving a localised VP wave, which can then be received on a vertical antenna. But the major propagation mode for HF signals which are not received via the ionosphere, is space-wave, same as at VHF and above, where the main loss of signal is due to cancellation between the direct signal and the reflections from the ground. True ground wave propagation is what occurs at MF and below, where vertically polarised signals are launched along the ground surface, and the propagation losses can be accurately predicted, knowing the frequency and the ground resisitivity. Just something to think about. 8) ---[Start Commercial]--------------------- World Radio TV Handbook 2003 is out! Order it now! http://www.amazon.com/exec/obidos/ASIN/0823059677/hardcoredxcom ---[End Commercial]----------------------- ________________________________________ Hard-Core-DX mailing list [EMAIL PROTECTED] http://dallas.hard-core-dx.com/mailman/listinfo/hard-core-dx http://www.hard-core-dx.com/ _______________________________________________ THE INFORMATION IN THIS ARTICLE IS FREE. It may be copied, distributed and/or modified under the conditions set down in the Design Science License published by Michael Stutz at http://dsl.org/copyleft/dsl.txt
