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## [TowerTalk] 80M dipoles/height gain

 To: [TowerTalk] 80M dipoles/height gain alsopb@gloryroad.net (alsopb) Mon, 23 Jul 2001 12:24:04 +0000
 ```Here are some EZNEC calcs of an 80 meter dipole at heights from 60' to 160' Clearly guys who get even dipoles high win. height max gain/angle half power angles 20deg gain 60' 6.52dbi/89deg 30deg 1.5dbi 80' 6.16dbi/52deg 23deg 2.16dbi 100' 6.38dbi/40deg 19,81deg 3.4dbi 120' 7.05dbi/33deg 16,56deg 5.0dbi 140' 7.84dbi/28deg 14,45 6.8dbi 160' 8.31dbi/25deg 12,39 8.3dbi The 20 degree angle point was chosen because it represents a point that the a point in the second peak of the eu arrival angle distribution with a large fraction of the total . (East coast, Washington DC) It says going from 80' to 160' one gains about an S unit in EU from the East coast. The 6-12 degree region contains the first arrival angle distribution peak. It takes a dipole at 160' to put much energy there. A vertical isn't the answer to cover these lower angles -- unless you have excellent ground conductivity. EZNEC shows that verticals are also poor performers at these angles there in areas of conductivities in the 2-5 range (my QTH is 2.5.) Of course, if your vertical antenna is on a salt marsh, you win. 73 de Brian/K3KO n4kg@juno.com wrote: > > I would not expect much benefit from a 2L80 at only 85 ft > which is barely over 1/4 WL high. The ground reflection at > 1/4 WL high is centered straight up. The free space pattern > of the Yagi is centered at the horizon. The vector product > will peak somewhere in between. You may want to model > a 2L80 and an 80M dipole at 140 ft and 85 ft and see how > much net gain you will realize from that configuration before > proceeding. You might be surprised to see little benefit > over a dipole at 85 ft. > > 40M antennas play VERY WELL from 70 to 100 ft so that > is a good choice. > > Tom N4KG > > >>>>>>>>>>> > > K7PUC wrote: > > I am planning on installing subject beam at 85' using the Orion 2800 > rotator--both already on hand. > These 80m yagi posting have me wondering what problems I may be facing. > My > plan is to install > one set of elements on the boom at ground level (crankup tower), raise > the > tower to vertical and > then rotate the boom 180 degrees. Lower the tower and install the > opposite > end elements. > > Never having had a tower higher than 35', I will appreciate all comments. > > BTW, I was mostly interested in a 40m beam but decided to add 80m! > > k7puc > > ________________________________________________________________ > GET INTERNET ACCESS FROM JUNO! > Juno offers FREE or PREMIUM Internet access for less! > Join Juno today! For your FREE software, visit: > http://dl.www.juno.com/get/tagj. > > List Sponsor: Are you thinking about installing a tower this summer? Call us > for information on our fabulous Trylon Titan self-supporting towers - up to > 96-feet for less than \$2000! at 888-833-3104 HREF="http://www.ChampionRadio.com";> > www.ChampionRadio.com > > ----- > FAQ on WWW: http://www.contesting.com/FAQ/towertalk > Submissions: towertalk@contesting.com > Administrative requests: towertalk-REQUEST@contesting.com > Problems: owner-towertalk@contesting.com List Sponsor: Are you thinking about installing a tower this summer? Call us for information on our fabulous Trylon Titan self-supporting towers - up to 96-feet for less than \$2000! at 888-833-3104 www.ChampionRadio.com ----- FAQ on WWW: http://www.contesting.com/FAQ/towertalk Submissions: towertalk@contesting.com Administrative requests: towertalk-REQUEST@contesting.com Problems: owner-towertalk@contesting.com ```
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