Re: Topband: Artificial Propagation...?
But more importantly, 100 km is too low to provide much help to us Topbanders. This is far below the E and F layers of the ionosphere that we rely on for DX. The peak of the nighttime E region is around 110 km, so 100 km is not too far below the E region. The lower E region is also where most absorption at night occurs on 160m. More to the point, refraction is inversely proportional to the square of the frequency. An electromagnetic wave at 1.8 MHz bends more and doesn't get as high into the ionosphere as our HF (3-30 MHz) energy. At night, with the E region critical frequency around 0.4 MHz, energy at elevation angles lower than about 5 degrees is refracted back to Earth by the E region. Thus the E region may be more important than we normally think. Carl K9LA ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Topband: solar max vs solar min
topbanders, In response to my posting, Per SM2LIY commented that the polar path at higher solar activity does not work good on topband. He is corret, and I should have added that qualifier. Carl K9LA ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Ionization before Japan's seismic event
Brian N9ADG posted: Interesting article talking about how the atmosphere may become more ionized over areas where there is increased tectonic plate pressure. There are quite a few papers in the technical literature analyzing the ionospheric signature of an earthquake (for example, I have papers on the M9.3 December 2004 Sumatra event, the M7.9 May 2008 Wenchuan event, the M7.6 January 2001 Bhuj event, and others). Trying to isolate a small earthquake signature in the ionosphere from the normal day-to-day variation of the ionosphere is a tough job, but the evidence is compelling that earthquakes do show up in the ionosphere. Tied to this concept are other longer-term events that couple up from the lower atmosphere to the ionosphere, and they no doubt play an important role in 160m propagation. This is likely why our simple efforts to correlate 160m propagation to just solar indices and geomagnetic indices generally fall short. Carl K9LA ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
