Topband: 5/8 wavelength vertical is mo betta than shorter versions??

Sun Sep 8 10:59:30 EDT 2013

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: armstrmj at aol.com
> Date: Sun, 8 Sep 2013 07:18:18 -0700
> To: w8ji at w8ji.com
> CC: topband at contesting.com; rodenkirch_llc at msn.com
> 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 significant
>  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" <w8ji at w8ji.com> 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