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
Topband: 160-Meter propagation
Topbander enthusiasts, On Dec 5 Brian VE7JKZ asked about solar flux in relation to 160-Meter propagation and wondered about solar min versus solar max. On Dec 6 Bob W7RH wondered if anyone has looked at space weather data with respect to propagation during ARRL 160. Also on Dec 6, George W8UVZ commented that the band isn't as poor as some would suggest. Those are three interesting comments, and they indicate that we struggle to understand propagation on 160-Meters, especially on a day-to-day basis. Propagation on 160-Meters is absorption-driven, meaning we usually don't have to worry about MUF as it is usually high enough to get a signal from A to B. The real problem is our lack of understanding of what's going on down in the lower E region (where absorption occurs at night since the D region is for all intents and purposes out of the picture for 160-Meter considerations). Efforts to correlate space weather (solar flux and K index) to the day-to-day propagation on 160-Meters usually don't give good results, as there's an important variable that's left out – events in the lower atmosphere coupling up to the ionosphere. This appears to play a big part in what's going on in the lower E region, but we have no parameter to measure this effect. Perhaps we will in the future, as scientists are developing physical models of the ionosphere (for example, GAIM out of Utah State University, which stands for Global Assimilation of Ionospheric Measurements) and they'll have to address this. Indeed, we're seeing more and more attention in the scientific literature paid to events in the lower atmosphere and how they affect the ionosphere. With respect to solar min versus solar max, the old adage that 160-Meters is best at solar min is somewhat of a self-fulfilling prophecy. We've heard 160 is worse at solar maximum, so we don't get on much then. Anyway it's easier to work the world on 10-Meters with S9 signals at solar max rather than signals at our noise level on 160. If you dig into the physics of the nighttime ionosphere at solar min and solar max, you won't find a huge difference. In my opinion, based on this and on log data by those who hang around on 160 during solar max, there's lots of DX to be worked at solar max, too. I remember W8JI worked over 200 countries and all 40 zones at solar max of Cycle 23 around 2000. Sure, he's got a great station and locale, but much of that effort was just being there day after day. In summary, I don't think we can predict propagation on 160 (interestingly, we can't precisely predict it on a day-to-day basis on HF, either). Also I don't think solar max on 160 is as bad as we think. And with signals near our noise level, small changes in the ionosphere in key places will contribute to some people saying 160 was wonderful last night while others will say we didn't hear a thing. For discussions of many of these issues, visit http://myplace.frontier.com/~k9la. 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
Re: Topband: Do Short Beverages Work?
Hi to everyone, I have a short (300ft) Beverage pointed ENE from my northeast Indiana QTH. Sometimes it helps with EU and sometimes it doesn't. I believe the cause of this variability is that noise doesn't always arrive from the same azimuth/elevation every night (kind of like the propagation of real signals!). So I don't think one should expect a short Beverage to perform the same at all QTHs - its usefulness will depend on the angles from which noise arrives. Picture the pattern of a short Beverage (wide main lobe with two small lobes off the back and nulls off the back and the sides) on the West Coast pointed to Africa and an identical short Beverage in the Midwest also pointed to Africa. Then put a noise-generating thunderstorm down in Mississippi. The Midwest station will say "my short Beverage works great" because the noise falls in a null off the side, but the West Coast station will say "my short Beverage doesn't help at all" since the noise is off the front side but not down that much because of the wide front lobe. Now complicate this with man-made noise and its azimuthal variability at different QTHs. It's been said here before and I'll say it again - the only good way to determine if something works is to put it up and try it for a while. Carl K9LA ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
