Jim - Your antenna research is impressive. I have downloaded the PDF and will spend some time studying it. Thanks.
One question I have relates to NVIS. In the case of my 80 meter EDZ, the plan was to make it workable for NVIS operation. It has succeeded in that regard very nicely in that I can cover the entire state of Illinois (which is primarily a N-S pattern) very well on both 80 and 160. We operate a state wide ARES/RACES net on 80m, but there has been some fear that as propagation continues to worsen for a period, the MUF for NVIS will require a higher frequency than non-NVIS and one that actually approaches the MOF at that time - due to the angle of radiation. In other words, using an NVIS antenna when the MUF is 4.0 MHz might actually require an MUF of 12 - 13 MHz which would be closer to the MOF at that same point in time. Have you observed that at any extremely low spot in the cycle? We have seemingly remedied that by setting up and operating a successful 160m net and passing digital traffic. 73 Lyn, W0LEN -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Jim Brown Sent: Friday, March 13, 2020 4:03 PM To: [email protected] Subject: Re: [Elecraft] Off-Topic: Your advice/suggestion about antenna On 3/13/2020 12:49 PM, Lyn Norstad wrote: > I actually do consider 4.7 dbi as "far outperforming" 2.14 dbi (ordinary dipole). It depends on what you want to achieve. The antenna you describe is a very old and well accepted design. It's like a beam with a fixed direction. No question that 2.6 dB can matter under marginal conditions. I have a 2-el wire 80M Yagi fixed on about 45 deg az that I can reverse to VK/ZL, which modeling shows gives me about that directivity. HOWEVER -- in this applications note, I showed that raising a 40M or 20M dipole by 15 feet will also increase gain at low angles by about 2.6 dB. See Figs 33 and 41, and the associated text. Doing this uses height to modify directivity in the vertical plane, without narrowing the horizontal beamwidth. http://k9yc.com/AntennaPlanning.pdf In the same app note, I also showed that mounting an HF vertical on a roof reduces ground losses and increases gain at lower vertical angles (below 30-40 degrees) than ground-mounting it. The differences show up for all soil conditions (except sea water), but are most pronounced for poor soil. I showed that the gain of vertical antennas is strongly affected by soil conductivity, while horizontal antennas are not, but are strongly affected by mounting height. And finally, I disproved the myth that antennas must be low for NVIS, that 75 electrical degrees is optimum, and that raising it to 120 degrees reduces high angle radiation by only 1 dB while increasing low angle radiation by 6 dB. Antennas are the component of our stations that are most strongly dependent on operator goals, real estate, the availability (and the cost) of suitable skyhooks or towers, their ability to reject local noise, and restrictions like HOAs, neighbors, and XYLs. No single antenna is best for all stations or operators. Antennas I can rig here in my redwood forest would be impossible on the city lot I owned in Chicago. :) 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
