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replies that seem to cover every "angle" on a problem that I had been thinking about. I very much appreciate all the thoughtful replies. I do know for sure that since late February, due to atmospheric conditions that on most days and most times, we have had more high angle noise than before. I have been doing A-B-C comparisons between an MA5B minibeam at 35', a 30M dipole at 35' and two Force-12 vertical dipoles - the Sigma 40XK and now the Sigma 5. I've worked very distant dx stations that I couldn't even hear on the MA5B, or which were so buried in the noise on the dipole that I couldn't work them. But the Sigma verticals worked like champs - not because of their gain - but most likely due to their TO angle and their ability to reject the high angle noise. I could just barely hear and work the dx - which is good enough for what I want to do. I do accept the fact that a full sized resonant monoband antenna (located at the perfect "place") would be best for each band, but that won't happen at my QTH. So I have learned that having a horizontal and vertical antenna to be able to switch between for all bands is a really good idea. I also have learned that having the resonant matching circuit at the feedpoint of a dipole is always better than (just) using a tuner in the shack. Using a tuner in the shack with the resonant circuit at the feedpoint works very well albeit with some (negligable) insertion loss - especially an L tuner. I have read the ON4UN Low Band DX-er book and many of the online Cebik articles - they are most excellent resources. Finally, (for my needs and goals) - I have learned that maximum antenna gain of the antenna is NOT the most important figure to look at when deciding on an antenna. The same for a receiver - I find that S/N ratio and adjacent channel rejection are as, if not more important than gain. I bought an old Ten Tec Omni V that is much quieter than my TS-2000. The received signals don't sound as "loud" but I've learned that "loud" is made up of signal and noise and nearby signals that affect what you are trying to concentrate on. Needless to say, I have learned after 30 years of being a ham that the stats that sales brochures present maybe true in the literal sense but many times practically speaking not very useful. Force-12 really does paint an accurate picture of what they sell and what the performance is. The same with Elecraft and Ten Tec - not too snazzy, but pretty down the earth and true. I will watch and see what happens over the next 2 seasons and see how they perform given that propagation will change and that the water soaked hills and pine trees will dry out. Our ground goes from being a soaked hillside run off area to a dry, cracked earth that actually opens up 1 -2" and goes for at least a foot deep. Its pretty bizarre. I will let you know if performance changes - I won't really know until I experience it. Robert Locher actually mentions a few "theories" proposed by dx-ers in his "The Complete DX-er" book. He says that a vertical antenna located up a hill on a shelf of the side of a hill should get some directionality. He said a hill is better than a ridge since the "null" that would be caused by the hill would only help null signals from / in that direction. This is exactly my situation . . . . The hill is composed of clay and sandstone, and like I said, the water run off keeps the bottom of the driven antenna support pipe (galvanized) steel wet all winter. The hill is steeper than the take off angle of the antenna, so it does seem that this theory might be valid in my case. This is the part where I feel "something" is going on that I can't measure - but that I will monitor this summer when things dry out to near desert conditions. Of course, the one variable I can't control is the propagation and the sunspot cycle. But I have been monitoring a few sites with data and have paid very careful attention to what signals can be heard when (especially the AM and PM gray lines). I keep spreadsheets with numbers and notes, and while this might sound like greenhorn science, it is a lot of fun to think about. (I'm a computer programmer not an EE or RF engineer). That's what does make this seem a little like magic - the fact that there are a number of variables beyond our control. I like the story about the sap in the pine trees. We have some Monterrey Pines not far away, and I understand how soaked they get in the winter and how dried out they get in summer. I guess I never saw them as a bunch of water pipes, but they sure are. 73, Rich KY6R ----- Original Message ----- From: "Jim Brannigan" <jbrannig@optonline.net> To: "Andrew Roos" <andrew@exinet.co.za>; "KEN SILVERMAN" <k2kw@prodigy.net>; "Rich Holoch" <rholoch@attbi.com>; <Force12Talk@qth.com> Sent: Friday, April 25, 2003 05:10 Subject: Re: [Force 12 Talk] RE: Sigma 5 Height (Cebik article) > Years ago I had a 40M/20M ground mounted vertical in a field. Three sides > were open, but because of a road it was positioned 20 feet from a dense > wood. > > In the winter it was a great performer. As spring approached and the sap > ran and leaves appeared, the performance would degrade. At first it seemed > due to seasonal propagation, but I finally realized it was those darn trees. > > Jim > > > > Cebik also mentions the point raised by Guy K2AV, that in the real world > > there are other considerations: > > > > "There is a counterweight to this facet of vertical antenna behavior that > is > > especially apt to urban, suburban, and wooded locations. I cannot > > demonstrate it with a model, but only from the collective experience of > many > > vertical users, including myself. The phenomenon is the dreaded "Rf-eating > > shrubbery." In the open fields of America's great farming states, a > > ground-mounted vertical has its best home, with nothing but open fields > for > > many wavelengths in any direction. In crowded locations, the presence of > > significant structures--both natural and man-made--appears to prevent a > > ground-mounted vertical from achieving its full performance potential. > > > > -------------------------------------------- > Force12Talk mailing list provided as a service by Force 12 Antennas, Inc. > Force12 Web Site: http://www.force12inc.com > > To Submit Message to the List: Force12Talk@qth.com > To unsubscribe and view the Message Archive: see http://qth.com/force12/list > For problems with the list: contact n4zr@qth.com > > -------------------------------------------- Force12Talk mailing list provided as a service by Force 12 Antennas, Inc. Force12 Web Site: http://www.force12inc.com To Submit Message to the List: Force12Talk@qth.com To unsubscribe and view the Message Archive: see http://qth.com/force12/list For problems with the list: contact n4zr@qth.com |
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