Because I was asked - Best Vertical

[HomerBB]

Some interesting quotes all from this source http://www.eham.net/ehamforum/smf/index.php?action=printpage;topic=75921.0:

If you read my comments carefully you'll see that I was comparing antennas with the same TOP height, not base height. The only reason that a 5/8 wave antenna has an advantage over a 1/4 ground plane with sloping radials is if the bases of the antennas are at the same elevation, in which case the point of maximum radiation of the 5/8 wave antenna is higher above the ground.

WB6BYU,
I have to disagree with your comments in Reply #5. You may not think, or may not have found there to be any legitimate differences between the various 'sizes' of antennas, but there are quite a few of us who have seen those so called 'magical' differences. That wasn't only on 11 meters by any means. I do agree that the 'gain' figures cited by some antenna manufacturers have to have originated in the advertising department. I don't happen to have an antenna range in my back yard so the comparisons I've seen personally are not exactly 'scientific' enough for some. But that's okay, I quite frankly don't care much, I know there are differences in gain between the 1/4 wave, 1/2 wave, 5/8 wave, etc.

I don't know why anyone would focus on tip height. Any antenna has a series of elevation nulls.

There are two things that determine the position of nulls.

One is where the various current peaks in the antenna occur, and this includes accidental or unintentional currents on the mast and the outside of the coax that everyone pretends don't exist, and the phase relationship of those current peaks.

The second effect is a multiplier by ground reflections that varies in angle of re-enforcement with height of the current maximums.

Together those things form the pattern, and where nulls appear. Radiation then occurs only where there are no nulls being forced, the result being a multiplication of the two effects.

Another factor, feedline and mast coupling, is virtually ignored. It is virtually impossible to fully decouple a feedline without having radials at the element base.

The bottom line is this. Aside from doing something wrong to reduce gain, there is no major difference between a 1/4 groundplane with sloped radials, a 5/8th wave vertical, or a 1/2 wave vertical when all are at the same mean height for current maximums. It is where the current maximum is that matters, not the tip.

Doc, I hope it is okay that I quoted your comments here. They are expressive of the thoughts of many, and are helpful in dialing in the reasons why antennas are perceived to offer performance differences between them - particularly why I report my impression of the differences I have seen between the antennas in the initial line up on this thread, and perhaps why Marconi has not seen so much difference between many of these antennas as others have reported.

Homer

 

[W5LZ]

Homer,
I really don't care. I don't think any post I make on a public forum is private, so if it's taken in context I don't see any problem at all, at least from me. Now 'eHam' may have a copyright problem but quite frankly, I couldn't care less.
- 'Doc

PS - BTW, I get $75 per word... is that gonna work?? oh well...

 

[HomerBB]

Sorry about the $75 per word thing. But you can attach this thread to your memoirs when they are published. It should help your book sales with folks knowing you were quoted by HomerBB.

 

[Marconi]

i do enjoy giving coily some crap for his claims sometimes ..... but he does build a damn fine looking tank of a antenna !!!

if he would put the same build quality and attention to detail onto a vector type antenna he could offer the baddest aaaz omni CB base antenna ever !!!!
IMO.
and it would even be worth the $400 - $500 he would ask for it .

BM, my only interest in Mr. Coily's antenna was to consider the coil design for matching a model of a .625 GP for Homer's idea in this thread. I tried Homer's coil dimensions and that did not seem to work out well at all, so I went looking elsewhere for something similar to see if I could get that to work on the model.

My intentions were, if I could get the matcher to fix the mismatch in the .625 wave antenna, then check and see what difference, if any, it made to the results in performance for the model. So far, I see very little difference.

 

[Marconi]

It is looking good. I think the length of my vertical may be only 22' on the one in the air. Too cold, and I'm too sick to go outside in the rain to measure it again.
As for which antennas to work up at current maximums, the Merlin, EFHW, 5/8

Homer, get to feeling better soon. I too have been suffering, but it was from side affects due to a new medication I started Thursday before Christmas.

The overall length of this model with a 4" inch diameter coil is measured from the top of the coil, at the end of my wire #74, to the tip.

This does not include the height of the coil and the wire below...down to the radials. The radials measure 96" + 12.5" for the short tips in you design. I think I used the same tapper schedule and tubing lengths that you suggested you might use earlier, and hopefully I didn't change anything there. If I'm able to get a feed point designed like the Coily setup, and it works with a good Average Gain result, then I'll measure overall length from the feed point to the tip, but for now just to let you know where I measured from and to.

I may have adjusted the top element to reach resonance, but I measure this model at 21.69' feet for the radiator above the coil and I show resonance at 27.205.

I'm not expecting your antenna dimensions and my model to be anything but similar in dimensions. You have a wire adding length from your feed point to the tap point, and this model does not show that. So, there is a difference. My radials are attached symmetrically, and yours may be off-set some (one above the other), like noted in the Coily image. That too can make for a little difference.

Can you be any more specific with captions maybe, as to which models you refer to above?

 

[Marconi]

Homer, here is the coil with the Coily type feed point added. As you'll note on the Source Data report, the match is not good. I haven't reduced the coil on this one yet to 4" in diameter, so maybe that will make things better.

View attachment 4.5'' coil with Coily feed point..pdf

 

[HomerBB]

I think the only models on this thread are these that are of the attempt to match the 5/8 with the Coily inductor.

I was just thinking if the possibility existed of using past successful models of a 1/4ƛ, a 1/2ƛ, and a 5/8ƛ with the current maximums at equal heights it would be informative.
I guess I'll have to shop around through some of the threads and locate a model of each antenna type and pull them together for redoing at the same current maximum.

 

[bob85]

which current maxima would you use for the vector if you included it in this comparison homer?

 

[HomerBB]

Well, Bob, I left this one out because of its peculiarity.
Were I to include it, I'd place it on the dominant 1/2ʎ or 5/8ʎ wave maximum of the vertical radiator.
It's fine with me if it is included. The peculiarity I refer to is the lack of universal enthusiasm for modeling the v4k in EzNec, not its RF characteristics.
If someone is willing to take on the task with that slick colorful modeling program that emanates and pulsates I'd be very happy for that, too.

 

[bob85]

i guess it would be nice to see the new and old style vector done in cst homer, + the astroplane and a few well known 5/8waves
i know which works best in my yard but i don't know how much the extra height above surroundings the longer old style vector benefits from has to do with it.

 

[HomerBB]

CST is interesting.
I know what I experienced, too.
More than likely the expense of CST will keep it out of circulation for some time.

 

[Marconi]

I think the only models on this thread are these that are of the attempt to match the 5/8 with the Coily inductor.

I was just thinking if the possibility existed of using past successful models of a 1/4ƛ, a 1/2ƛ, and a 5/8ƛ with the current maximums at equal heights it would be informative.
I guess I'll have to shop around through some of the threads and locate a model of each antenna type and pull them together for redoing at the same current maximum.

I think you're right Homer. A while back I emailed you a list of models where I made sure the model settings were as close to the same as I could get them, and those were all set at the same tip height. If you're referring to those models, maybe you can check your emails from me and ID those captioned names, and let me know which ones you want compared at the same current maximum heights. And if I get your 5/8 wave setup with the matcher included working right, then I'll add that one to the mix also.

You'll likely have about as much luck shopping around and finding models that truly compare on other threads, as you would have winning the Texas Lotto, but good luck if you try.

 

[Marconi]

antennas that operate on the same principles are in the text books eddie,
i never doubted what CEBIK told me, the proof is in the cst plot,
its the falacy that its a simple 1/2wave that's not in the text books,

the results obtained by the people who bothered to buy or build the 4 radial extended version and make it work correctly still puts a smile on my face,
i don't see a que forming to complain i was pulling their todger.

Bob, I see what you and Shockwave see in the CST model for the Vector, where constructive contribution is produced with the top 1/2 wave and the bottom 1/4 wave. It looks pretty convincing to me. I just can't prove it using Eznec. Thus far nobody seems to want to discuss why the currents it sometimes produces are not always consistent with expectations.

Eznec can and does indicate correct phasing and current flow in my vertical stacked collinear 1/2 wave however, so I know it can produce the affects in that simple construction using the proper phasing stub. <gotproof>

I can also make this same antenna look bad in this regard...just by changing how the wire ends are positioned in the model.

Can you, or Shockwave tell us what the length of radiator and radials were in this Sirio CST model?

Was it a model of their New Vector 4000 per chance?

You may have posted this information before, but could you tell us approximately how tall your Vector radiator was from the feed point to the tip, and how long were the 4 radials...when you noticed the best performance at a distance?

Homer of Booty Monster, I think you've both had conversations with Bob about his Vector, do you know generally what any of his dimensions were, in case he doesn't see this?

 

[Shockwave]

The CST model is shown with a 1/2 wave top element like the new Vector. This can be determined by noting the model has all radiation currents in a constructive phase. If it were the old 7/8 wave we would see approximately 1/8 wave of the vertical radiator above the cone, out of phase with the rest of the antenna much like we do in a typical 5/8 wave. I don't have access to any old Vector CST models and I'm not aware of any.

The longer length used in the new cone is producing improved performance. Bob and myself both noticed this years before the new Vector came out deviating from the old 94 inch length. This has to do with the fact the cone is not just a 1/4 wave radiator, it must also be positioned correctly so that it covers the bottom 1/4 wave of the vertical. Combine this with the velocity factor between the cone and the vertical and you can quickly see there are several different areas affecting the optimal alignment.

I've found .82 wavelength from the feedpoint to the tip gives the best performance. Bob feels that these lengths can be altered to tailor the angle of radiation to best suit a particular installation. Many would be quick to deny this fact assuming only height above ground could impact TOA. We have a "non apparent collinear" here and with two active elements radiating, beam tilt is possible by altering the phase angle between the two. I don't think that was considered when the antenna was shrunk back down to 3/4 wave.

 

[tuner]

Great Thread ! Thanks !