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Author Topic: Real time Comparison with HEX Beam and Mono Band Mosley Yagi will be interesting  (Read 13081 times)
KF6ABU
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« Reply #30 on: February 15, 2011, 11:51:35 AM »



Now how about this HEX Beam, Here is what manufactures claimed, all you need is 30 to 35 ft, and this match any 3 element mono bander even if it is 10 ft or 20 ft higher..Believe me, I called them all and they all same the same thing Now, Mosley claims they have a 3 Element Yagi that can achieve more than 8dB above a dipole while only using 3 Elements on a 24 foot boom..
I will put the Mosley at 40 FT, and the HEX Beam is already at nearly 30 FT…OK, Let’s see…I will be on the air for all to compare, for at least 3 months…I love doing stuff like this…Again, I could care less who wins, I just purchased both of them,..
I will start these A B Tests around March 15.

This is a joke right? I think you are either trying to make a funny, or trying to make a comparison of products without actually thinking first.

Dx Engineering's site, wihtout even opening the manual states:

The DX Engineering MARK 2 HEXX antenna offers gain and front-to-back performance that exceeds your expectations for a 2 element beam.  Its unique shape is much smaller, better balanced and has been reported to receive less noise than typical beams. This lighter, easier to handle antenna can be rotated with a light duty rotator, and it performs well - even when mounted in the clear only 20 to 30 feet above the ground.

I dont think a single "educated" person would believe a folded yagi (hexbeam) can beat a mono band non trapped yagi at any height.

You claim you were told that, I doubt it. Based on what you have said I pretty much would doubt your claims about ANYTHING.

I'm not sure what you are trying to prove. Thus far you have tried to prove, through future tests that a 3 el monobander will outperform a 2 el hex beam. What will you try and prove next? The sun is hot? I'll spare you trouble.. It is.
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K3JVB
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« Reply #31 on: February 15, 2011, 04:35:38 PM »

I have a traffie 5 band Hex.

No doubt it works fine. Small foot print,only 20 pounds. But it will not perform as well as a longer boom mono-bander. It is what it is. A two element beam. 3 db forward gain..maybe. Decent front to back.
Great for many, maybe not for all.

No magic , just a good design....not a three element beam. IMHO
73
John
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N4JTE
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« Reply #32 on: February 15, 2011, 08:58:39 PM »

Wow, not sure why most of the posts are so vitrolic, the hex beam site claims 6db of gain over a dipole at the same height on 20 meters.
Well 6dbd of gain is comparitable to a three element monobander so why not put it to whatever test he can devise?
Bob
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N4JTE
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« Reply #33 on: February 15, 2011, 10:01:33 PM »

With ionospheric communication the HEX-BEAM's performance is comparable to larger conventional designs, and averages an apparent gain of 6dBd. A/B comparison tests were conducted at frequencies of 7-147 mHz. during an 8 year period. A summary of these "on air" tests is shown by the RP , from the website!
N4JTE
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N3OX
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« Reply #34 on: February 15, 2011, 10:07:53 PM »


With ionospheric communication the HEX-BEAM's performance is comparable to larger conventional designs, and averages an apparent gain of 6dBd.

Apparent gain.  That's a cute term.   Undecided 
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Dan
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KD8MJR
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« Reply #35 on: February 16, 2011, 09:28:59 PM »

I say go for it, the results will be very interesting.

I am not all that old, but one of the things that I have observed in the last 10 years is the tendency for computers and the Internet to just stifle true innovation.  Yes I said that, and yes I know some of you are laughing your butts off, but it's true.  I like to experiment, and so many times I have heard people say OH that will never work, a quick search on the Net showed that you just cant do that!  Yet in many instances I get it done.  Just last week I had such an experience and the guy who said it shook his head in disbelief.   If people depend on NEC programs to tell them everything then not a whole lot of innovation will ever occur because I would bet good money that there are antenna designs that could be made that will show totally unexpected and different results from what a NEC model will show.

Anyway I know it's hard to argue this point, because computers do make great things happen, but at the same time they seem to limit this generation of engineers from thinking outside the Box.
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N3OX
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« Reply #36 on: February 17, 2011, 07:14:02 AM »

I am not all that old, but one of the things that I have observed in the last 10 years is the tendency for computers and the Internet to just stifle true innovation. 

You're thinking of the wrong people.  Much of the technological progress we see in 2011 relies almost entirely on computer-assisted design.  GOOD models of electronic systems work very well, and good models, creatively used, lead to innovation.

You don't have to be a professional engineer to make GOOD models of antennas.  You do have to spend time on it, and never stop learning tips on how to do it properly.  You have to make predictions and then you have to check them (or have other competent people help you check them) and see how the "real world" is different from the prediction.  This is good science. 

If you look at enough GOOD model/measurement comparisons, you start to see a pattern: outrageous claims based on computer models of antennas are often the result of some really flawed models where the MODELER made a serious mistake.  People leave out the feedline on antennas that are prone to common mode problems.  People neglect to include the 30 foot mast standing 20 feet away from their 40m vertical.   Often, people use the wrong type of model for the earth, breaking some numerical rules that are explicitly stated in the manual.  People don't do self-consistency checks on the model to see if the calculations are running into difficulties or not.  Some people base claims on models that show 300% efficiency because the calculation engine is choking on the problem.  Again, the way you check this is discussed in the manual, but some people don't bother.

This is not the fault of the computer tools.  It is a classic case of garbage-in, garbage-out.  If you don't know how to build good models and check for basic problems with the predictions, you're going to generate nonsense.

Quote
If people depend on NEC programs to tell them everything then not a whole lot of innovation will ever occur because I would bet good money that there are antenna designs that could be made that will show totally unexpected and different results from what a NEC model will show.

There are some antennas that don't lend themselves well to NEC simulation.  Some examples of this are antennas with lots of close spaced wires, lots of sharp corners near other sharp corners,  and antennas with tightly coiled parts that don't lend themselves well to approximation with lumped loads, like some helical antennas. 

But the flip side of this is that there are some antennas where free NEC-2 programs can predict the performance more precisely than any of us can actually measure.  Tubing and rod beams with elements insulated from the boom installed in the clear are common on the higher HF bands and VHF/UHF.  These are predicted very well, even by relatively inexperienced modelers.  If you spend some time reading G3TXQ's hexbeam pages, you will see what kind of impressive agreement you can get between models and measurement when an experienced, careful modeler and tester works on it.  You'll also see that some of the differences between the models and the real world measurements were the result of assumptions of what could be left out of the model, not because of a deficiency in the modeling tools hams have available.

Don't let some blowhard with a "quick web search" or a flawed NEC model with too many simplifications make you think that computer tools stifle innovation.  For many of us, computer tools lead us in new directions that we NEVER would have had the time or resources to go without them.  And even slightly over-simplified models can often result in built antennas that work "good enough" in the real world with no adjustments. 

It's been a long time since I put up an antenna I thought was going to be better than what I have already and found that it was worse.  It's been a long time since I had to spend more than five or ten minutes tuning an antenna, and even then, I didn't have to cut wire.. .I just had to twiddle a capacitor in a matching network a twentieth of a turn.    Not all of these antennas measure exactly the same as the predictions, but they're close enough that there's not much point in tweaking them, and they're close enough that errors in my measurements, especially on a small lot with limited time, are probably more serious than errors in the models.

===========

If you don't LIKE modeling stuff and you just like to go outside and experiment, that's great!  Do it!  But don't be excessively skeptical of modeling in general.  Be careful and test things, but don't assume that models can't describe reality when done well.  They can.    And don't assume that measurements are free of errors and problems.   Measurements also have a set of strong assumptions and antenna interactions can be a SERIOUS problem.   Measurements can generate nonsense just as much as models can.  Maybe more.  People will argue that their 80m double bazooka is 18dB better than their 80m dipole, and then you find out they hung up the two antennas about 0.2 wavelength apart and therefore built themselves a wire beam... and really that 18dB is just 10dB because of an "S-unit" assumption.  People will sometimes invent things out of thin air when their measurements show one antenna to be surprisingly better than another.  They thank their good luck and move on, firmly believing their mistake was a result of a good measurement.

Don't get me wrong: real-world measurements are very important.  They're very satisfying and make you feel good about your antenna.  They're important checks for modelers.   But they're very messy and error-prone, and if you want to ACTUALLY know things to within a few dB it is very difficult and time consuming.  If you don't do the difficult and time-consuming part and you don't give enough space between antennas, you're just fooling yourself.   Richard Feynman put it well in talking about science in general:

Quote from: R.P. Feynman
The first principle is that you must not fool yourself and you are the easiest person to fool.

Honestly, the hams I trust most to know how antennas work are people who model things and then make sure that those things get measured, and then think really hard about any differences.  Models help tell you what you're doing wrong with your measurements and measurements help tell you what you're doing wrong with your models.  So people who do both are constantly "checking their work" in a way that ensures they don't fool themselves.

Other people who FULLY trust anything NEC programs say without even doing the self-consistency checks are fooling themselves.  And people who "measure"  two tightly coupled antennas, who assume that 6dB per S-unit is a universal truth, and people who do a couple spot check "measurements" and call it a day are also fooling themselves.   

Quote
at the same time they seem to limit this generation of engineers from thinking outside the Box.

What box do you want people to think outside of?  Professional engineers have full three-dimensional finite element software that solves Maxwell's equations for anything.  And if you're thinking of thinking outside the box of established electromagnetic theory you've got a huge body of work to overcome.  We have tested the heck out of electromagnetic theory.  It is  simply an excellent predictor of how electromagnetic fields behave.  As with any scientific "fact," classical electromagnetic theory is subject to change as we discover new things.  But those new things will come from subtle and exotic experiments that cost millions of dollars.  There will be no antenna breakthroughs based on someone discovering new physics in their backyards.  Anyone who says they have "new physics" on their side is either trying to sell you something or really fooling themselves or both.

There are lots of new ways to use the established physics (like metamaterials), but many of those really need computers to search for good, weird designs in the infinity of possible antenna designs.  It is possible to luck on to a good weird design in your backyard.  I won't deny that.  But then you really have to make sure it's as good as it seems, and that requires more testing than most people do.  People are scared of having their "innovation" debunked.  But it's not an innovation unless it stands up to serious attempts to show that it's NOT an innovation.
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Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
STAYVERTICAL
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« Reply #37 on: February 17, 2011, 02:04:24 PM »

Dan (N30X) makes a very compelling and accurate argument about the veracity of good mathematical models in predicting real world outcomes, as would be expected from a professional scientist.
But, to some extent, herein lies the problem with both ham radio and many other pursuits these days.
There is amnesia from many people that ham radio is a hobby, a diversion, a recreation activity, not a peer reviewed government grant funded scientific program.
The modern reliance on models by "professionals" leads to laziness, and non-imaginative thinking.
When we look at most of the modern foundations of physics, electronics, mathematics, and many other scientific areas, the fundamental axioms were laid down by people not using models and computers.
Many of these insights were "eureka" moments which are peculiar to the human race.
Einstein, with his riding on a beam of light, Kekule with his snake eating his tail benzene ring are examples of the imagination and peculiar power of the human mind to transcend simple iterative thinking.
To elevate models above their place as a simple tool, is to deify a hammer for helping you build a house.
Today, there is a still a great divide amongst pure mathematicians who seek to further the art by thought and those who use models to either iteratively or deductively prove truths.
A neural network, for example, is despised by those who would seek to use an algorithmic analysis of problem solving, but they are both extremely useful, and in fact the basis of our brains.
If, as Dan said, the models were used with skepticism, they would be an extremely useful tool - but like relying on the output of a calculator without doing a quick sanity check of the answer, you could end with truth which is a lie.
Modern day examples abound of so called professional scientists using models with, as Dan said, garbage in garbage out.

The English met office, with its vast arrays of supercomputers and professional modellers can't even predict massive snowstorms which have hit the country for the previous three years.
Nasa, with massive computer power and expertise can't predict the sunspot cycle will be a weak one, instead predicting a massive one which never happened.
Global warming models have been shown to be laughable and best used as comedy skits on late night TV.

Yes, if models were used by scientists without built in biases, and without funding depending on giving a certain point of view, they would indeed be valuable.
But, in todays world of lobby groups and money going to where the models outputs is most desirable, I think I will put more faith in the backyard experimentalist.

73s
« Last Edit: February 17, 2011, 02:16:20 PM by STAYVERTICAL » Logged
KD8MJR
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« Reply #38 on: February 17, 2011, 03:11:14 PM »

Amen StayVerticle Amen...
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KD8MJR
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« Reply #39 on: February 17, 2011, 03:21:47 PM »

Dan very nice write up, and it's true that given a person uses a modeling system properly they will most likely get accurate results, the problem for me is that modeling programs are now used in Realms were the outcome of such can be inaccurate and in these cases a possible break through is overlooked because a modeling program says it won't work.  A perfect example of this is all these bloody weather modeling systems, they seem to be as accurate as just looking at a Satellite picture and taking a guess!   In cases like this if the human brain was used a bit more I bet some obvious reasons would be found, but instead people will plod along trying to tweak the current algorithms because no one wants to admit the software may be working with algorithims that are missing many small but vital components that just cant be worked out without a human  discovering whats missing by using pure grey matter research.

All in all I find myself worried for my own kids, I see a world emerging where the skill sets of most kids have no real value except in the cyber world.
« Last Edit: February 17, 2011, 09:41:06 PM by KD8MJR » Logged
K1BQT
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« Reply #40 on: February 17, 2011, 06:55:12 PM »

Anybody thought about E-plane nulls? Isn't it possible that, over ground,  the higher gain Yagi will exhibit deeper E-plane nulls than the Hex so that signals at SOME arrival angles might actually measure stronger on the Hex? Of course the larger antenna will wipe its butt at all other angles, but the manufacturer probably forgot to write those data points down! Same for the H-plane pattern, too, where the Hex has less directivity. Wink
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G3TXQ
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« Reply #41 on: February 18, 2011, 03:55:44 AM »

I don't think you'll see any significant difference between the on-axis elevation pattern of a 2-el hexbeam and a 3-el yagi. The Gain advantage is predominantly caused by the difference in azimuth patterns.

Steve G3TXQ
« Last Edit: February 18, 2011, 03:57:32 AM by G3TXQ » Logged
G3TXQ
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« Reply #42 on: February 18, 2011, 04:36:06 AM »

I view the antenna modelling issue very differently from STAYVERTICAL.

Whilst developing the broadband hexbeam I found that the availability of EZNEC actually encouraged innovation. I had many ideas about how the antenna might be improved, but I could never have evaluated all those ideas experimentally within a sensible time frame. EZNEC modelling allowed me to discard the least promising ideas and focus my practical experiments on the most promising.

When the practical work started, the close agreement between EZNEC predictions and my measured results gave me confidence that the ideas which I rejected because of modelling results had not caused me to "miss a trick".

For me, the ability to test ideas using modelling is a real encouragement to innovate.

Steve G3TXQ

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K1BQT
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« Reply #43 on: February 19, 2011, 04:20:50 AM »

I don't think you'll see any significant difference between the on-axis elevation pattern of a 2-el hexbeam and a 3-el yagi. The Gain advantage is predominantly caused by the difference in azimuth patterns.

Steve G3TXQ

Two different Yagis -- one with significantly more gain -- mounted at two different heights over real ground won't exhibit significant differences in E-plane pattern nulling? I can't agree, but perhaps a little modeling will prove me wrong!

Rick  K1BQT 
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G3TXQ
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« Reply #44 on: February 19, 2011, 04:43:00 AM »

Two different Yagis -- one with significantly more gain -- mounted at two different heights over real ground won't exhibit significant differences in E-plane pattern nulling? I can't agree, but perhaps a little modeling will prove me wrong!
Rick,

I should have been more explicit. My comment applies to antennas at the same height over the same ground. A Dipole, a 2-el Yagi, a 3-el Yagi all have very similar elevation characteristics - the gain differences predominantly come from the concentration of energy in azimuth.

That comment becomes less valid as you increase the number of Yagi elements.

73,
Steve G3TXQ

« Last Edit: February 19, 2011, 04:45:41 AM by G3TXQ » Logged
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