Hi, Carl Well, yes, high angle radiators have a definite advantage in dealing with hilltop or mountain top repeaters as I pointed out in one of my earlier posts/replies. My experience with 160 is significantly more limited than my VHF/UHF experience, and my experience with high angle radiators on 160 is limited!
Regards, Charlie, K4oTV -----Original Message----- From: Carl [mailto:[email protected]] Sent: Sunday, September 08, 2013 4:54 PM To: Charlie Cunningham; 'Shoppa, Tim'; [email protected]; [email protected]; [email protected] Cc: [email protected] Subject: Re: Topband: 5/8 wavelength vertical is mo betta thanshorter versions?? Contrary to one persons views that 2M ham 5/8 antennas are pure rubbish sounds about what Id expect from a flatlander. As anyone who has spent decades in a hilly or low mountainous area knows, the 5/8 antenna can knife edge refract over hills via that high angle lobe and access the wanted repeater. At other times the multipath is tolerable but annoying. The 5/8 also helps in concrete canyons. I have several VHF/UHF commercial repeaters here on top of the highest hill in 20+ miles and the users select the commercial mobile antenna that works best for them. They are a mix of simple 1/4 wave for the close in locals to a selection of 5/8 and collinears, all from recognized commercial antenna manufacturers, for those requiring a lot of 20-50 mile travel ranging from the ocean to the 200-700' hills of NH and MA. It has also been shown time and again that a high angle can be very beneficial on 160 DX as shown by the success of inverted L's and a low inverted V or dipole. I owe several new DXCC to a low inverted V and would not be without the V and 1/4 wave vertical with elevated radials; they complement each other. If you live in another part of the country or world things may be different. Carl KM1H ----- Original Message ----- From: "Charlie Cunningham" <[email protected]> To: "'Shoppa, Tim'" <[email protected]>; <[email protected]>; <[email protected]>; <[email protected]> Cc: <[email protected]> Sent: Sunday, September 08, 2013 1:12 PM Subject: Re: Topband: 5/8 wavelength vertical is mo betta thanshorter versions?? > > > > > > All, > > There has been a lot of "cussin', and discussin' " on this reflector > regarding 5/8 wave and shorter vertical and perceived merits. There have > also been perceived insults, irritation and hurt feelings! > > I spent a little time last night and some this morning modeling some of > these cases with EZNEC. I chose 40m, because I had an array stored, that > I > could pull out the driver and use it as a quick model, without doing a lot > of construction with EZNEC. In the attached Word document there are > figures showing the antennas and their current distributions along with > elevation plots and data. See above. > > All of the radiators were modeled above 4 elevated resonant radials at 10' > above real high-accuracy ground. > > Note the following: > > * The gain of the 1/2 wave vertical increases approximately 0.3 dB > over the 1/4 wave ground plane, and its takeoff angle is reduced about 5 > degrees, from 22 degrees to 17 degrees. (The angles are, of course, height > dependent.) > > * Neither the 1/4 wave or half wave verticals have any noticeable > high-angle radiation. > > * The 5/8 wave radiator brings the main lobe down another 3 degrees, > from 17 degrees to 14 degrees elevation and the main-lobe "gain" is > increased another 0.2 dB., but, in this case, there is a high-angle lobe - > that peaks above 50 degrees elevation, and is only 2 dB below the main low > angle lobe. > > > It is this last point that has led, I expect, to most all of the differing > perceptions of the merits ( or lack of) of 5/8 wave verticals! > > When we consider HF propagation via the ionosphere, the high angle lobe > can > produce a reflected sky wave that can produce either destructive or > constructive/reinforcing interference with the lower angle main lobe > signal! > ( If we were discussing VHF/UHF we would call this "multi-path" > interference!) > So the result is that at varying distances from the transmitter we can can > have concentric bands or areas of either constructive, or destructive > interference. > All of this is further complicated by different atmospheric ionization > conditions in different directions from the transmitter and time of day ( > where the "terminator" or grey-line is) etc. > > So the perception of whether a 5/8 radiator may be superior or inferior to > a > shorter radiator, can be very dependent on distance frequency, time of day > etc. > If one has a regular schedule with a fixed end point, or endpoints, that > happen to lie within a region where there tends to be constructive > sky-wave > reinforcing interference at that frequency and time-of-day. But this is > unlikely to be true on all paths, I expect. > > I hope this helps to shed some light, but this is all the time that I can > put into it at this time. My apology! > > Best regards to all! > Charlie, K4OTV > > > > -----Original Message----- > From: Shoppa, Tim [mailto:[email protected]] > Sent: Sunday, September 08, 2013 11:27 AM > To: '[email protected]'; '[email protected]'; > '[email protected]'; '[email protected]' > Cc: '[email protected]' > Subject: Re: Topband: 5/8 wavelength vertical is mo betta than shorter > versions?? > > I have been told by others, (treat as hearsay), that for AM broadcasts the > 5/8 wave produces a pattern with destructive interference between skywave > and groundwave at medium distances at revenue-important times of day e.g. > "Drive time". > > Tim N3QE > > ----- Original Message ----- > From: Charlie Cunningham [mailto:[email protected]] > Sent: Sunday, September 08, 2013 11:17 AM > To: 'James Rodenkirch' <[email protected]>; 'Mike Armstrong' > <[email protected]>; 'Tom W8JI' <[email protected]> > Cc: [email protected] <[email protected]> > Subject: Re: Topband: 5/8 wavelength vertical is mo betta than shorter > versions?? > > Jim, Mike et al: > > I've been putting together a document along with some models, plots etc. > that addresses the 1/4, 1/2, 5/8 wave vertical question, and I hope, > illustrates where some of the confusion arises - especially with regard to > the 5/8 wave case. The answers are not so simple in that case, and are > dependent on distance, frequency, time of day, and ionospheric conditions. > Please keep your cool and bear with me. Maybe we can shed some light on > this > complex issue, with a little less heat and cussin' and discussin'! I'll > post > the document on the reflector as an e-mail attachment. > > 73, > Charlie, K4OTV > > -----Original Message----- > From: Topband [mailto:[email protected]] On Behalf Of James > Rodenkirch > Sent: Sunday, September 08, 2013 11:00 AM > To: Mike Armstrong; Tom W8JI > Cc: [email protected] > Subject: Re: Topband: 5/8 wavelength vertical is mo betta than shorter > versions?? > > Mike: I apologize if my query came across as an insult!! Mea culpa sent > from out here in the black hole of 160 meter communications - s/w Utah. > I think I said I wasn't doubting your claim and I wasn't questioning your > "conclusions" - just attempting to find some modeling or Measures of > Performance to substantiate it as, lately, I have been seeing/reading of > anecdotal "evidence" and I, for one, am interested in supporting > data/measurements. > I use/employ a 43' vertical on 160 through 17 but can't compare it to a > 1/4 > wave over the same radial field -- certainly your closeness to the water > may "answer" or provide a reason for your success with a 5/8 over 1/4 so, > with the modeling info I supplied perhaps someone who knows the modeling > apps(s) could do some "investigating" in the form of modeling to answer > that?!?~! > OK?? 72, Jim R. K9JWV > >> From: [email protected] >> Date: Sun, 8 Sep 2013 07:18:18 -0700 >> To: [email protected] >> CC: [email protected]; [email protected] >> Subject: Re: Topband: 5/8 wavelength vertical is mo betta than shorter > versions?? >> >> Tom (and James), >> I am well aware that my comments concerning the 5/8ths wave was based >> upon > subjective/anecdotal evidence. I am in a science (Astrophysics) by > profession..... I do know the difference. HOWEVER, I cannot completely > throw out the simple fact that when I altered my 20 meter omni antenna for > Winlink to the 5/8ths, that I received UNSOLICITED comments from the > system > users stating (100 percent of them) that my signal was much improved into > the areas they happened to be sailing. None of those people, not a single > one, knew that I was changing my antenna. The purpose being just > that..... > to see if anyone complained or said anything else concerning performance > from THEIR point of view. In reality, THAT is the point when supplying a > service..... What do the USERS think of the performance, not what I think > or > what a FS meter says. >> >> Even if I had the equipment to measure the performance and the equipment > says that my signal should be improved, but the Winlink user comes online > and universally states my signal sucks, I will REMOVE that antenna. I > know > that isn't likely, but if the modelling software states the signals should > be worse and they are, 100 percent, reported as improved, then there is > something at play that the modelling software isn't taking into > account........ >> >> Not arguing, just answering that initial question that from my EXPERIENCE > with that antenna, it works better than the quarter wave at the same > locations I happen to be...... AND ONLY ON 20 meters. I won't speak to > any > other band, although I would think it would work there, too, because I > have > not put one up for those other bands. >> >> As an aside, alot of folks are using that so-called non-resonant vertical > antenna that is roughly 43 feet tall....... They seem to be having some > success with them on the bands. Physically, they are pretty > convenient..... > and on 20 meters, they happen to perform pretty well, judging from user > comments, anyway..... and at that band, it is roughly 5/8 wave in > electrical > height. So, again, I find it interesting that actual experience argues > with > the modelling software (in MY particular instance). But, again, in my > case > IN HAWAII, I had an outstanding location that, for some reason I don't > know, > happened to favor the 5/8 by alot more than even the theoretical gain > would > indicate. NOBODY would comment, much less 100 percent of commentors, on a > slight gain of 2 db. Heck, that wouldn't be worth the effort. However, I > think you are quite right, Tom..... something else is at play.... ground > clutter (I had some.... loads of tropical trees and plants in the area), > some significa > nt >> ly tall sailboat masts RIGHT ACROSS THE STREET from my house (very > close), etc, etc. Then you consider the seawater ground that was so close > by...... There are many factors to take into account, not much of which > does > a modelling software take into account. Undoubtedly the answer is there > and > not directly related to antenna gain. I did try elevating it on top of a > 40 > foot pipe mast and using 8 resonant radials....... it made no difference > except to increase the chances that high winds would knock it down. In > terms of SUBJECTIVE performance and comments, no difference. So, I put it > back on the ground and carried on. >> >> Remembering what the antenna was for, and where it was located, putting >> up > a horizontal 80 or 90 feet in height simply wasn't possible. The SERVICE I > was providing required OMNI directional capability, so even a dipole would > be unsat in at least 2 directions...... those being the directions an > emergency call would not be heard...... Not a good situation for the given > purpose, right? >> >> I will say that I didn't appreciate the comment concerning how I came to > my conclusions about antenna performance. Insults only prove that one has > run out of reasonable arguments..... and that is ALL it proves. Given > that, > this will be my last post here and I am likely removing myself from the > list. Insults are NEVER science...... not now, not ever! >> >> Mike AB7ZU >> >> Kuhi no ka lima, hele no ka maka >> >> On Sep 7, 2013, at 18:59, "Tom W8JI" <[email protected]> wrote: >> >> >> The above modeling results just don't support that contention/posit so > I'm wondering what else comes in to play that could lead folks to love the > 5/8 wavelength vertical over a shorter version, regardless of frequency? > I > don't see one performance comparison that supports that claim. I'm not > saying the "claiming person" isn't correct but....I don't see how! >> >> Help - what am I missing here? >> >> 72, Jim Rodenkirch K9JWV >> > >> > The 5/8th wave obtains the small amount of gain it has through effects > of ground reflection. The current maximum is elevated, and that elevation > causes additional phase shift with the illumination of earth out some > distance from the antenna. The re-radiation of earth is sometimes > explained > by an "image antenna". The image antenna is a fictitious antenna directly > below the real antenna, and this "image antenna" simply represents what > the > earth at a distance does from the illumination from the main antenna. >> > >> > The 5/8th wave moves the current maximum slightly higher than a quarter > wave above earth, so the fictitious image moves slightly lower than a 1/4 > wave below surface. >> > >> > If you move the 5/8th wave above earth, such as in a groundplane well > above the earth, the extra length no longer provides gain. Instead, it > actually reduces gain at low angles. >> > >> > Another effect is the extra height above ground of the high current >> > area > can help get the antenna's main radiating area a little bit higher above > ground clutter. >> > >> > This would also apply to an extended double zepp, where the second > antenna half makes the image unnecessary. Each half of the double zepp is > the image of the other side, so we don't need earth. >> > >> > So it is a very specific benefit from the 5/8th wave caused by moving > the current height up above a reflecting surface, or in the case of a > double > zepp moving current away from a second identical element while still > having > a common center feedpoint. >> > >> > One of the biggest antenna hoaxes played on people was the 5/8th wave >> > CB > groundplane antenna. Two meter 5/8th wave groundplanes are the same. The > work on the broadcast band to increase groundwave signal because soil is > often reasonably low loss on the AM BCB. If the soil out some distance > from > the antenna is lossy, or if it does not exist, the 5/8th length causes > increased low angle loss. >> > >> > This is why when you look at models, outside of specific cases like >> > some > cases of low broadcast band use, we have a tough time seeing the gain > imagined or claimed. A field strength meter has an equally difficult time. > :) >> > >> > 73 Tom >> > _________________ >> > Topband Reflector >> _________________ >> Topband Reflector > > _________________ > Topband Reflector > > _________________ > Topband Reflector > > _________________ > Topband Reflector > > > ----- > No virus found in this message. > Checked by AVG - www.avg.com > Version: 10.0.1432 / Virus Database: 3222/6147 - Release Date: 09/08/13 > _________________ Topband Reflector
