The 5/8-Wavelength Antenna Mystique

[Marconi]

I have argued multiple times that as you angle the 1/4 wave radials down on a 1/4 wave antenna that the antenna as a whole acts less and less like a ground plane vertical and more and more like a dipole. I see no reason why the same wouldn't be true for a 5/8 wave groundplane antenna with 5/8 wavelength radials and an extended double zepp antenna.

I might think the same thing DB, and there have been discussions about doing that very thing. I guess the idea most talked about is it will make the 5/8 wave have a better match, but my models don't support that idea like it does with a 1/4 wave radiator...an antenna that really needs a good ground system in the setup.

My 5/8 wave models also indicate very little difference in gain and no difference in angle when the idea of slanted radials is applied vs. horizontal radials.

My only concern for this last link is it is in freespace, and not near a simulated earth ground. It would be interesting to see how a real ground being some distance under such an antenna would affect it.

I know he writes some of his images are in free space, but you can look as the patterns and tell they are not free space models. One image also says it is an azimuth view as well, and that is either BS or my ignorance one.

Plus this guy says he was using Eznec Demo, and it has sever limitations allowing us to only use 20 segments. The models I used here are close to 100 segments, and that is a segment length of 1' foot long on average for all elements. IMO, that is too long for segments.

Another thing to mention, I have several times in the past on this forum mentioned that I would like to play with a vertical extended double zepp, and every time someone says it would be a cloud warmer. I was never so sure about that as how I apply what I know of antenna theory disagrees with that postulate. The article you linked in the first post of this thread also disagrees with what I have been told by multiple people. In the "Where 5/8-Wavelength Pays Off" section it does state that such a vertical antenna will still have real gain on the horizon, however it does not provide any pattern of such a setup at any distance over real earth.

All that being said, there is definitely a difference between radials of any size and a theoretical "perfect" ground plane of "infinite size and infinite conductivity". Even with radials of 2, 3, 4, 5, 10, or 20 wavelengths long, it is still not the same, therefore the "mirror effect" that such a ground plane presents is incomplete at best. Therefore, if you limit yourself to 5/8 wavelength radials and angle them down as mush as you can, would that not help complete the "mirror effect" as you are physically (and electrically if I am not mistaken) closer to the ideal 5/8 wavelength antenna and its electrical mirror?


The DB

I don't know much if anything about the mirror effects, but there is discussion in the article. Maybe when we hear talk about a double zepp, the discussions are typically ham related, and about horizontal wires. IMO the EDZ seems to require more height and works better at lower frequencies well below 11 meters...or else it will produce maximum RF at a higher angles than may be desired. I have a model of two 5/8 wave radiators stacked vertically and it looks to provide some good gain, but it is very tall and that alone will limit its use in 11 meters.

Homer made a remark about the subject of "edge diffraction" a while back, and that has something to do with why the patterns for these antennas tend to fail in reaching the gain levels that an antenna over infinite ground can attain...the theoretical gain theory in this study.

My only point in this thread is that CB ideas about gain for these vertical antennas may have come from information in this study and this review. Maybe what we hear repeated claimed about the gain for the 1/4, 1/2, and 5/8 wave radiators may have been misunderstood, misrepresented, or just ignored...based on what might happen with these antennas over real Earth.

 

[nav2010]

Marconi wrote

So, what is the truth, is the 5/8 wave idea as good as many in the CB World claim, or are we destined to ignore the truth?

Are you suggesting that a quarter wave ground plane is better than an i10K, a Sirio 827, Mr Coily, etc at AM, FM and DX?

or are we destined to ignore the truth?

But does your version of the truth use real world events rather than that crock of pants Eznek software that Doc probably wrote

 

[Marconi]

Marconi wrote

Are you suggesting that a quarter wave ground plane is better than an i10K, a Sirio 827, Mr Coily, etc at AM, FM and DX?

But does your version of the truth use real world events rather than that crock of pants Eznek software that Doc probably wrote

No 2010, IMO you're wrong on both counts, but I can post some Eznec models that will support what is claimed here.

I hear all the time about the big signal differences folks see when comparing the different antennas like you've noted here.

I posted this link, because I think it may well be the defacto work that the common CB street idea about antenna gain is derived from. At least the theory part of the article is very close to a lot of real world claims on the subject.

I've also read work by guys like Cebik, W8JI, and others, that seem to indicate that the signal from a good 1/4 wave radiator with a suitable ground plane can work just about as good regarding gain, as these other longer antennas. I also see that here when I compare RX signals side by side.

I have not made the following claim here, but on occasion I've also add my own results to suggest that I might not always see as good of signal as the bigger antennas I have, but sometimes I can hear better.

My point was to draw attention to the results and limitations in this review where it seems to clearly point out, to me, that a 5/8 wave antenna does not produce a 3 db better signal that a 1/4 wave antenna, except in theory, and over an infinite conducting ground plane.

Cheer up 2010, this is just rag chewing...and it ain't gona' change the world one bit.

 

[IRock817]

I picked up a never been assembled Penetrator 500 for $40.00 last night. The guy threw in a used bottom section of an old one. Good deals don't come very often and it's great when it happens. Oh and picked up 163 ft of 7/8" Heliax for $100.00 with the ends installed and 160 some ft of 1/2" Heliax for 40.00. Yeah me!

 

[The DB]

I have a model of two 5/8 wave radiators stacked vertically and it looks to provide some good gain, but it is very tall and that alone will limit its use in 11 meters.

Very tall, yes. Over 40 feet tall. That and having to find a way to center feed it makes it difficult at best for 11 meters. I may play around with one for 2 meters sometime though... Even then, it takes quite a bit of gain to actually be noticed in the real world with the equipment I have available to me...


The DB

 

[Marconi]

I picked up a never been assembled Penetrator 500 for $40.00 last night. The guy threw in a used bottom section of an old one. Good deals don't come very often and it's great when it happens. Oh and picked up 163 ft of 7/8" Heliax for $100.00 with the ends installed and 160 some ft of 1/2" Heliax for 40.00. Yeah me!

That is a good deal 817. Did you get the manual? HyGain made several different models over time, and the new version may also be a little different. You might not be able to tell just looking at it however.

 

[The DB]

Are you suggesting that a quarter wave ground plane is better than an i10K, a Sirio 827, Mr Coily, etc at AM, FM and DX?

I will tell you right off of the bat that there is far less of a difference over the relatively small artificial ground planes used than many people are willing to admit.

But does your version of the truth use real world events rather than that crock of pants Eznek software that Doc probably wrote

When it comes to modeling software the problem with bad models isn't the software, it is the person doing the modeling that doesn't fully understand the software they are using. I am not saying EzNEC doesn't have its drawbacks, but the problems and incorrect information that people get with its outputs are not the programs fault. In my experience, RF modeling is as much art as it is a science. If you don't understand your tool then blame the tool for your mistakes, is it really the tools fault?


The DB

 

[nav2010]

When it comes to modeling software the problem with bad models isn't the software

I disagree, the software is only as good as the person who programmed it and the knowledge he had at the time. Unfortunately Eznec cannot emulate nature, it can only emulate one persons version of how nature works.

 

[IRock817]

Got the manual!
Says 22' 91/2"
Copyright 1975

 

[The DB]

I disagree, the software is only as good as the person who programmed it and the knowledge he had at the time. Unfortunately Eznec cannot emulate nature, it can only emulate one persons version of how nature works.

Here you have stated a belief, now show me what you believe is true.

NEC based software, including EzNEC are based on algorithms that were first used in the MiniNEC BASIC program, and expanded on with the NEC-2 package. This information goes beyond the "one persons version of how nature works" idea you present. I am not saying that any of them are perfect, but they do have their place.

Antenna modeling is a tool, just like that fancy antenna analyzer that you hopefully use. If I show someone who has only ever known SWR meters for tuning antennas the output of my AIM4170C do you really think they would have any idea what they were looking at or what to do with the information provided? The same goes for using antenna modeling software, including EzNEC.


The DB

 

[nav2010]

Here you have stated a belief, now show me what you believe is true.

NEC based software, including EzNEC are based on algorithms that were first used in the MiniNEC BASIC program, and expanded on with the NEC-2 package. This information goes beyond the "one persons version of how nature works" idea you present. I am not saying that any of them are perfect, but they do have their place.

Antenna modeling is a tool, just like that fancy antenna analyzer that you hopefully use. If I show someone who has only ever known SWR meters for tuning antennas the output of my AIM4170C do you really think they would have any idea what they were looking at or what to do with the information provided? The same goes for using antenna modeling software, including EzNEC.


The DB

Doesn't matter who's software or who's algorithm it is based on, it is still programmed my men. Men are not mother nature, they base their software on what they think is a reasonable simulation of mother nature.
The computer game 'Total war' is a computer simulation of a war, there are no real swords or spears thrown and people dying.
Eznec is the same, there are no antennae, no transmissions, no people, no houses but just a simulation of such.
Therefore its only as good as the men that programmed it.
If they made a mistake or two then its a pile of horse manure - period.

 

[nav2010]

....And just to add to that, back here I'm known as Doctor Nav. I've just developed my new software for analyzing people called surprisingly 'The Doctor Nav People Analyzer' TDNPN for short. This software is also based on the NEC MiniNec algorithm but also the Turbostrad technology just recently developed.
I've just inputted the data which you and Marconi have released and its saying 'your both off your tits'.
Can't be wrong DB, NEC says so.

 

[Lil'Yeshua]

Sounds familiar
The 5/8-Wavelength Mystique

 

[The DB]

....And just to add to that, back here I'm known as Doctor Nav. I've just developed my new software for analyzing people called surprisingly 'The Doctor Nav People Analyzer' TDNPN for short. This software is also based on the NEC MiniNec algorithm but also the Turbostrad technology just recently developed.
I've just inputted the data which you and Marconi have released and its saying 'your both off your tits'.
Can't be wrong DB, NEC says so.

Haha, funny. You don't seem to have anything to back your claim/opinion so you resort to jokes.

Here you have stated a belief, now show me what you believe is true.

Joking aside, I'm still waiting for more than an opinion from you on this. Do you have anything to back up your claims?

Sorry for the thread hijack Marconi.


The DB

 

[nav2010]

Haha, funny. You don't seem to have anything to back your claim/opinion so you resort to jokes.



Joking aside, I'm still waiting for more than an opinion from you on this. Do you have anything to back up your claims?

Sorry for the thread hijack Marconi.


The DB

What do you want me to prove? I didn't state a belief but rather a fact, Eznec cannot emulate real life. It cannot take into account attenuation, it cannot take into account the difference between the materials our houses are made out of, coax differences, differences in soldering techniques, antenna switches that Marconi uses that are poor quality, flat ground as apposed to hilly ground. Its a free space emulator which isn't valid in the real world.
In the real world where I live, quarter wave GP's do not perform as good as 5/8th waves, .64 or open sleeve antenna's. How do I know? Because I've had 2. Besides that I know people that have had them and they also believe they don't perform as good. Not saying they don't work just saying they don't perform as good as a 5/8th wave. If they did then everyone would have one because they take up very little space.
With antennae, the money is where the performance is around these parts and no matter what Eznec says that will always be the case.