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Author Topic: home-brew sigma 4 11 meter antenna  (Read 78568 times)
MARCONI390
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Posts: 17




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« Reply #105 on: November 16, 2013, 09:17:57 PM »

Stop trying to pit me and Bob against each other. You know more about Bob's exchanges with Cebik than I do. I didn't know he actually got to speak with him. Bob has also recently indicated to you he's not pleased with the way you reword the things he's described to you to fit your thoughts rather than attempt to understand them.

I'm just curious, why would seeing Cebik's opinion on the antenna outweigh CST's confirmation of his opinion years later? What's to prevent you from just saying "you typed it up" like you refer to the CST model as "my animation"? Cebik's opinion to me just gave the encouragement that Bob and myself were on the right track. CST and the collinear field testing with adjustable phase shift proved it.

You know Donald, I really for a lot of reasons hope you are right. At 76, I have nothing to loose, but maybe a little pride in getting something wrong, and maybe loosing two buddies I respect...simply for having questioned them on a antenna. You are the one exposed here Donald, and that can't be fun.

Like I've said before, I don't know enough to be so categorical in what I understand in modeling, but  I try and tell what I think I see in my model. If Eznec does what you claim, then I will benefit by knowing that. I will go on to something else, and you and Bob will receive much support and gratification for hanging in with your beliefs and getting what you see too, right.

We all win that way, except again, I may loose two buddies.

I've said my piece, and I'll wait for the results. This bickering between us is not fair to WB6BYU. He has something at steak here too, and I appreciate his efforts to try and answer some questions. I also think we need to give BoothMonster some credit for having the courage to bring is antenna project to this forum what ham operators that are willing to listen and help.

I would like to know how to post an EZ file here on eham, if anyone has a suggestion.

Thanks again WB6BYU and any other's with comments on this topic,

Eddie
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KE1IZ
Member

Posts: 30




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« Reply #106 on: November 16, 2013, 09:37:29 PM »

Marconi, just remember my confidence comes from being able to reproduce the same results I claim in the field along with every client I've worked with except one. I've done nearly the exact same tests being described now and have no reason to believe if W6BYU builds a 2 meter version of the Vector and tests it for gain at a distance, he will see similar results.

In an effort to eliminate his concern that his prototype may not replicate the design accurately enough to satisfy me, I'm willing to send him an FM broadcast version if he can do the receive tests against a distant signal on this band. I'll include return shipping and all I ask is you send it back after your test regardless of the outcome.
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KE1IZ
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Posts: 30




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« Reply #107 on: November 16, 2013, 11:11:28 PM »

The last sentence in my first paragraph above should read "no reason NOT to believe". Sorry for the typo.
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WB6BYU
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Posts: 13477




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« Reply #108 on: November 17, 2013, 07:53:32 AM »

Let's take it one step at a time.  While I appreciate the offer of an antenna to test, I want
to start with one that I build for a band where I have more test equipment available,
and multiple other antennas on hand to run comparisons.  Once I get the initial results
we can consider where to go from there.  I may be able to rope a couple other hams from
work into the project as well at that point.

Measuring gain on a distant signal isn't as easy as it might appear. I have an antenna
switch in my van so I can compare two different VHF mobile antennas, and the relative
positions on the roof and exactly where I'm parked make more difference than the
two antennas I'm actually trying to compare.  The best method I've found is to switch
back and forth as I drive down the road and try to average the S-meter readings,
giving a result such as "this one tends to read slightly higher than that one."  That's
because we have a lot of multi-path in among the hills.  Even trying to mount two
antennas on the same mast is subject to changes in height, common mode currents,
and small shifts in position due to wind or mast wobbles.

This is even more complicated on FM BC signals due to the use of circular polarization,
as some shapes of phasing stubs will pick up more of the horizontal component than
others.

That's one reason why I want to try using the same radiator element in a securely
fixed position and just swap the matching sections, because that reduces (though
not entirely eliminates) some of the variables.   If the antennas really are different
in free space, then I should be able to measure that difference, even over a shorter
distance (>10 wavelengths across my back yard.)


It would have been easier at the old house, which was on a bit of a hill in the country.
I could hit repeaters ~100 miles away running 250mW, and could place a signal source
up to a mile away pretty much line of sight.  But now we're on a suburban lot and what
antenna building materials I've kept are stashed away in the attic.  I don't even have
any ham antennas up yet.  (And I have CC&Rs to contend with, but I can work around
those.)  First priority is trying to put away enough stuff that we can get a car in the
garage over the winter - that's been my project for the last 3 weeks, and I still have
a long way to go.  So please be understanding if I don't get around to running any
tests right away - we're in the middle of a major life change.  But an occasional
reminder certainly won't go amiss...
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KE1IZ
Member

Posts: 30




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« Reply #109 on: November 17, 2013, 12:08:56 PM »

WB6BYU, I'm gaining confidence in your desire to test this antenna in an unbiased setting. You recognized that a CP station could effect the perceived gain due to the phasing element being in the horizontal plane. That actually did prove to be a significant problem during my first field test experiments. Knowing that full power commercial stations use CP in the USA, I began looking lower on the dial in the public section for a low power VP station.

Since I already had the dipole assembled to compare against, it was real easy to lay it horizontal and look for stations that only had signal present in the vertical polarization. Back then I didn't have access to $20,000 in test equipment so it took some time to prefect my test equipment to insure I was receiving accurate results. The receiver I selected then was a Marantz with a high quality tuned front end and signal meter.

Problem was its input impedance was 75 ohms and the signal gain would not peak in the correct place with a 50 ohm antenna unless I readjusted the gamma match. Then it showed a poor VSWR. Sweeping the receiver input and aligning it to 50 ohms became mandatory. I took the risk of popping the MOSFET in the front end and connected the MFJ into the antenna input and began the test.

Adjusting the RF input coil and the section of the tuning capacitor that made the front end track the frequency provided near perfect results across the entire band. Realizing the built in signal meter and receiver AGC circuit would never allow accurate gain measurements, started getting me to think of a way around that variable too.

The signal meter was disconnected and wired into a digital volt meter with resolution down to one hundredth of a volt. Using a dipole receiving a VP signal, the exact voltage was measured on the DVM. The dipole was removed from the mast and coax to be replaced with the Sigma design. Using a calibrated attenuator the signal received by the Sigma was reduced to the same DVM reading as the dipole. At no time during any of the tests did the Sigma model measure up less than 2dbd. Any variable between tests was always less than 1db.
« Last Edit: November 17, 2013, 12:16:13 PM by KE1IZ » Logged
WA2OOO
Member

Posts: 1




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« Reply #110 on: March 18, 2014, 08:09:15 PM »

Well what's the news if any on this subject?? The testing is what's holding this up??  Really?? 
My own 2 sense...... I have a home in Vermont on 300 acres, it was a farm at one time it is at 1500 feet of elevation with a 360 degree view of the horizon. And on this farm:

I have three antenna towers housing various antennas at different times
I ran my own tests of this antenna against 
Hygain 5/8 wave Penetrator, and the More robust versions being built today,
1/2 wave ground planes
1/2 wave vertical dipoles
1/4 wave ground planes
1/4 wave stub multiband verticals on 10 meters ( Hygain AV-640, Cushcraft R-6000 )
supposed 5/8 wave Imax 2000's
Antron 99's.

Once upon a time it was my belief that there was NO Antenna that could out perform a true sized 5/8 ground plane antenna such as the Penetrator

Since testing this antenna, my opinion has changed. The Sirio Vector antenna outperforms them all, meaning the most gain at the lowest elevation lobe of any of them.
Yes I have EZNEC and have modeled this antenna and countless others. Gain for this antenna coming in at 2.41 dbi free space. It really doesn't matter what EZNEC says

All arguments aside, the antenna just flat out works very well. It may have some qualities no one has figured out yet, and EZNEC I personally doubt can address it.
I have built dozens of antennas after modeling them with EZNEC only to see expected SWR points appear at different frequencys then observed. And this is with the feedline isolated and using non-conductive masts.


It reminds me of another antenna no one including Cebik himself could fully explain the mystique, although he Loved them... The Cubical Quad.
I also emailed Cebik about Quads and the earlier version of the 4000 antenna, when he was alive and he wasn't sure EZNEC would model this antenna correctly.
There are no shortage of Yagi enthusiast who are oh so quick to say that the Cubical Quad isn't really better then a Yagi on the same boom length. And they have no shortage of reasons as to why it shouldn't be.
And yet None of these experts have ever built and used Any Cubical Quad antennas! And there are none to be seen on any of their QRZ pages!
I am not getting into this debate myself, I have gotten my answer by looking at the antennas on QRZ pages built by the strongest stations I have heard around the bands years ago.


I suggest we have the same issue here. The Vector 4000/ Sigma 4  antenna has the same problem, it can't be explained accurately through modeling, It isn't easy to explain it through paragraphs of antenna theory either
and unfortunately since it was born a CB antenna, it gets dismissed easily, even though 90% of hams started in CB, and they still have never built a homemade antenna.

My response to anyone who dismisses it without ever building one themselves is this: What kind of expert are you? Without building and testing one you cannot prove your own argument! So what's the point??
If someone with a design of an antenna comes on the forum, that you disagree with the results, because you learned EZNEC, your making a novice mistake. Go build the antenna yourself and prove your own theory
no matter what it is.

To be clear I don't know any of the other Hams/people on this forum, But I do know a good antenna when I get it on the air. And this is a good one.


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WB6BYU
Member

Posts: 13477




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« Reply #111 on: March 19, 2014, 07:30:58 AM »

Quote from: WA2OOO

Well what's the news if any on this subject?? The testing is what's holding this up??




Well, we still didn't get a car in the garage over the winter, and now have a pile of soggy
soil dumped in the driveway so we have to park on the street.  An otherwise busy winter
was further complicated by a death in the family and getting laid off at work, with now a
daunting job search ahead.  I still don't even have a workbench available.

I appreciate the reminders, and still think about the problem occasionally, but Real Life
has kept me busy.  The experiment should be simple enough that someone else could
run it if they were interested.  I'll get there someday if there is still interest, but at the
moment I have higher priorities.
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MARCONI390
Member

Posts: 17




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« Reply #112 on: March 19, 2014, 11:34:08 AM »

WA2000, thanks for your comments, but I don’t consider the Sigma4 (S4)/New Vector 4000 (NV4K) to be better or worse than some of the other vertical CB antennas you mention above.

In my real world testing I don’t see nearly as much difference in performance as others tend to claim. Even Sirio claims the NV4K has 4.15 dbi gain in free space so I'm told, but they don’t indicate any angle for this claim. I'm not even sure their claim is in free space. The best my Eznec free space model shows for the NV4K is 2.49 dbi @ 3* degrees.

I don’t recall anybody posting a claim that the S4/NV4K designs were ineffective or bad in any way…excepting maybe someone posting that they could not get their S4/NV4K to work or tune up right. The performance I see in my real world testing and with my Eznec models is also good…it just isn’t as good as some are claiming including what Sirio publishes.

Your quote here:
All arguments aside, the antenna just flat out works very well. It may have some qualities no one has figured out yet, and EZNEC I personally doubt can address it.

My ideas for how this design performs is pretty much the same as yours I think…it performs very well. However you suggest there are qualities that no one has figured out yet, and that Exnec probably can’t address. I disagree, because I have never noticed anything so distinctive in real world operations with this antenna. I think Eznec probably is showing us pretty close to what we might expect for such a model and it shows a bit better than a vertical 1/2 wave dipole at the same height to the current maximums.

To me any disagreement we might have on performance values noted here are likley based on the magnitude of differences in Free Space performance we might tend to accept. I also claim that the only advantage in performance that the S4/NV4K might have over a vertical 1/2 wave diopole is the added height of the current maximum...when both antennas are mounted at the same antenna base height, which is close to 1/4 wavelenth or more in height advantage for the S4/NV4K.

As I've noted above my Eznec model shows pretty close to what you claim for your own Eznec model. Can you describe your thinking as to what you envision is indicating Exnec cannot address the qualities you noted?

Could also give us some comments as to some details for your testing that revealed the new information that changed your mind about the NV4K?

In your testing, how did you determine the most gain, and the lowest elevation lobe?
« Last Edit: March 19, 2014, 11:53:24 AM by MARCONI390 » Logged
BOOTYMONSTER
Member

Posts: 73




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« Reply #113 on: July 20, 2014, 11:19:31 PM »

i find it amazing that my dumb CB antenna has generated more views and more post than any other topic in the homebrew section  Grin

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N0SYA
Member

Posts: 369




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« Reply #114 on: July 21, 2014, 08:14:11 AM »

i find it amazing that my dumb CB antenna has generated more views and more post than any other topic in the homebrew section  Grin



Raja on that, breaka!
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If you have a clumsy child, you make them wear a helmet. If you have death prone children, you keep a few clones of them in your lab.
MARCONI390
Member

Posts: 17




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« Reply #115 on: July 28, 2014, 08:45:54 AM »

i find it amazing that my dumb CB antenna has generated more views and more post than any other topic in the homebrew section  Grin


BM, how about a report on how your antenna is working out.
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