The BCB stations migrated from 1/2 and 5/8 wave antennas, diamond shaped towers, and mountain tops by the early to mid 30's as they started to understand how things worked...or didnt.
Carl KM1H ----- Original Message ----- From: "Guy Olinger K2AV" <olin...@bellsouth.net> To: "Richard Fry" <r...@adams.net> Cc: <topband@contesting.com> Sent: Sunday, May 06, 2012 10:05 AM Subject: Re: Topband: Monopole Radiation Patterns, takeoff angles etc > Hi, Rich. > > I guess one could ask why bother with this mid-field analysis. It IS > TECHNICALLY TRUE what you say, no argument, but of little use since you > don't get to keep it, UNLESS you can get it over salt water, or off a > mountain top. The far field code in the various programs is adding up the > gains AND THE LOSSES and presenting you with the sum, rather than giving > you the loss in one presentation, the gain in another and making YOU add > them up in your head. For myself I will stick with the convenience of > letting the program do the subtracting. You are talking about salary > before taxes. I can only spend take-home pay, and I can only make QSO's > with the take-home pattern. I don't see anything wrong with using the > take-home takeoff angle as the item of conversation -- it's the one you > get > to use. > > 73, Guy. > > On Sun, May 6, 2012 at 8:44 AM, Richard Fry <r...@adams.net> wrote: > >> All vertical monopoles of 5/8-wavelength __and less__ radiate (launch) >> their >> maximum relative field (E/Emax) in the horizontal plane. This is true no >> matter what the loss in the r-f ground connection they use. >> >> A lossy ground connection will reduce the gain of the antenna system, but >> it >> will not change the relative fields they radiate. IOW, their pattern >> shapes >> remain the same regardless of the loss in the ground connection, be that >> to >> salt water, or dry sand. >> >> The link below leads to a plot of the radiation patterns and >> directivities >> of >> several monopoles. These are the shapes of the radiation patterns >> leaving >> the monopole as they exist at the beginning of the far field of the >> radiator. >> >> These patterns were calculated for two ohms of loss in the r-f ground >> connection - which is about the loss that 120 x 1/4-wave buried radials >> provides even in poor soil. If fewer/shorter radials are used, then loss >> increases and the directivities (gains) of these patterns would be >> reduced -- but the radiation pattern shapes would remain the same. >> >> Many amateur radio operators consider only the far-field pattern of a >> monopole antenna as shown by NEC and in textbooks, without realizing that >> this is not the shape of the radiation leaving the monopole. It leads to >> the concept of a "takeoff angle" where radiation apparently was maximum >> from that monopole. >> >> However the elevation field radiated by a monopole always is maximum in >> the >> horizontal plane, and always is less than that at the elevation of an >> assumed takeoff angle. A NEC analysis including the surface wave from >> the >> monopole will show this. >> >> Some of that low-angle radiation can reach the ionosphere and produce >> skywave service, even though according to a NEC far-field analysis, the >> fields are approaching zero at those low angles. >> >> This doesn't mean that radiation at and near the "takeoff angle" does not >> provide significant skywave service, but it does mean that significant >> skywave service can be generated by radiation at much lower angles than >> commonly believed. >> >> http://i62.photobucket.com/albums/h85/rfry-100/MWElPatComparison.jpg >> >> _______________________________________________ >> UR RST IS ... ... ..9 QSB QSB - hw? BK >> > _______________________________________________ > UR RST IS ... ... ..9 QSB QSB - hw? BK > > > ----- > No virus found in this message. > Checked by AVG - www.avg.com > Version: 10.0.1424 / Virus Database: 2411/4981 - Release Date: 05/06/12 > _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK