Dream Antenna

[ka7niq]

I wouldn't say that low (somewhat undefined) loops are a waste of time. On the fundamental frequency, they are great for high angle coverage on links 0-300 miles. Just depends what you want.

Some good info on phased dipoles at the link below.

http://www.eham.net/articles/27922

Even before I read this stuff, I have had a few low loops up, over the years.
All were simply insulated wire, strung through trees for support.
Of course, they all broke, and I was nearly always forced to go back to a Dipole.
I never seemed to miss a lick with the dipoles, local or dx.

Then, I found this

Which is the Best 160m Antenna ?

In a nutshell: vertically-polarized antenna for transmitting, using separate antennas for receiving.

From W8JI on qrz.com:

"The fact is....... an Inverted L with 20 or more radials at least 50 feet and hopefully 100 feet long will absolutely smoke any normal height loop antenna or dipole antenna at nearly any distance on 160 meters. The possible exception is between 20 and 200 miles.

"As a matter of fact a low full wave loop has no gain, any horizontal wire has increased earth induced loss as it is made longer when close to earth.

"Do not make the radials shorter just because you have fewer radials. They really need to be as straight and long as possible, but lengths over 100 feet don't help much. Even 20-30 radials 60 feet long make a fairly good ground.

"Nearly all especially successful stations on 160 use a vertically polarized antenna of some type for transmitting. That's just a fact.

"I have a full size 160 dipole at 300 feet, and it is never really much better than a 1/4 wave vertical at any distance in any direction. As a matter of fact, the dipole is 10-20 dB weaker than the vertical off the dipole ends. The dipole only beats the vertical broadside to the dipole, and then only rarely!! And this is with the dipole 300 feet above ground.

73 Tom"


http://forums.qrz.com/showthread.php?t=260716&highlight=beverage

[Steve - K4HX]

The facts are that antennas are almost always about tradeoffs. The tradeoff with an Inverted-L is likely reduced signals on shorter range links. This might not matter much since usually signals are strong on short links anyway. Losing a few dB isn't going to matter. The other tradeoff with an Inverted L is the requirement for a ground radial system. The payback is stronger signals on longer distance links. Each person must weigh these tradeoffs for themselves. What sort of contacts do they want to make? How much time, effort and money will be put into the antenna system? How often will they use the band in question? Will/can the antenna be used on other bands? A hard core DXer on 160 meters will answer these questions and weigh the tradeoffs differently than someone looking to make a few short range AM contacts on 160 meters during the winter months only.

[The Slab Bacon]

There will be many naysayers out there, but my antenna works surprizingly well!
It kicks ass on 40 and 75 and even works surprizingly well on 160.
But............. You need heavy feedline and a balanced tuna with serious cajones to make it work. Don't even think about using anything made by MFJ if you are considering running any serious power! ! ! ! The whole trick is to get as much of the RF as you can to the feedpoint of the antenna. Depending upon what power level you are running, the feedline current can become pretty brutal, especially on 160. I primarily use it on 75, but have been known to occasionally pop up on 160..........


Frank

[ka7niq]

There will be many naysayers out there, but my antenna works surprizingly well!
It kicks ass on 40 and 75 and even works surprizingly well on 160.
But............. You need heavy feedline and a balanced tuna with serious cajones to make it work. Don't even think about using anything made by MFJ if you are considering running any serious power! ! ! ! The whole trick is to get as much of the RF as you can to the feedpoint of the antenna. Depending upon what power level you are running, the feedline current can become pretty brutal, especially on 160. I primarily use it on 75, but have been known to occasionally pop up on 160..........


Frank

Even an 88 ft doublet is quite short for 80 meters, as can be seen here. http://www.w8ji.com/short_dipoles_and_problems.htm

Your antenna is only 60 ft long.

W/O seeing the modeling results of this antenna/feedline combo, here is what it looks like to me is going on.
You may have "hit" on a good feed line length, that combined with your wide range tuner, is allowing you to force feed power into it.

But just because we can feed power into it, doesn't mean there is not considerable loss in the matchbox/feedline.

You can easily be losing 3 to 6 db with this combination on 80 and below, and that is before the loss of the overly short dipole is added in.

If it were me, I would start over, and instead use the wasted bottom folded dipole wire to add some length to the top dipole. Zig Zag it to fit your yard if you have to, but more length in your flat top is what you need.

[Steve - K4HX]

The antenna is longer than 60 feet electrically. There is 120 of wire involved. The losses have been well covered in other posts here over the last 10 years. The losses are minimal and probably indistinguishable from a full-sized dipole. Frank has made 1000s of AM QSO on 80 meters, some coast-to-coast. The losses are minimal and probably indistinguishable from a full-sized dipole. About the only improvement he could make is to increase the height above ground.

[W2VW]

Call me when you can engineer a 160 antenna that makes people know who to turn it over to next

[ka7niq]

The antenna is longer than 60 feet electrically. There is 120 of wire involved. The losses have been well covered in other posts here over the last 10 years. The losses are minimal and probably indistinguishable from a full-sized dipole. Frank has made 1000s of AM QSO on 80 meters, some coast-to-coast. The losses are minimal and probably indistinguishable from a full-sized dipole. About the only improvement he could make is to increase the height above ground.

Yeah, I just saw that. The furnished PDF File loaded on my screen sideways, and I don't read very well that way.
It is a bent in half 120 ft flat top, electrically.

The spacing between the top and bottom 1/2  of the dipole could be played with on the computer model I suppose, to try and get the most benign low bands impedance curve.

[The Slab Bacon]

Call me when you can engineer a 160 antenna that makes people know who to turn it over to next

+1 ! ! ! ! !      

[The Slab Bacon]

The spacing between the top and bottom 1/2  of the dipole could be played with on the computer model I suppose, to try and get the most benign low bands impedance curve.

What you need to do is use your commputer and your modeling software to print out as much worthless paper as you can and stack it beside the porcelain convenience for "those messy cleanups........."

Then turn the computer off and start modeling with wire! ! ! !  You'd be amazed at what you might discover! ! !

If half of the people out there took the time they spent computer modeling in search of the "holy grail" and actually built some antennas you would have a lot more QSOs out there.

No one said it better than the words of Derb! "Put as much wire as you can fit up as high as you can get it and feed it with ladder line, and a good tuna and no one will have trouble hearing you!"

"Nuff said! ! ! "

[ka7niq]

The spacing between the top and bottom 1/2  of the dipole could be played with on the computer model I suppose, to try and get the most benign low bands impedance curve.

What you need to do is use your commputer and your modeling software to print out as much worthless paper as you can and stack it beside the porcelain convenience for "those messy cleanups........."

Then turn the computer off and start modeling with wire! ! ! !  You'd be amazed at what you might discover! ! !

I have only been a Ham for around 25 years, not nearly as long as many of you.
I agree with you that computer modeling has taken a lot of the good old fashioned fun out of just going out, and actually building something, then seeing how it actually works, on the air!

However, that being said, I still think computer modeling does have a place, in the overall scheme of things.

Hell, I remember back in the old days, when we made Yagi's, we simply cut the reflectors and directors about 5% shorter then the driven elements, spaced the elements evenly across the boom, and went out hunting DX.

Yes, these antennas "worked", and some worked real well.
However, they would be no match for the computer optimized Yagi's of today.

Same with your antenna.

It seems you have a great design, from what all the guys here have said.
Now, what IF that great design you have come up with, could be made even better, by computer modeling.

What IF computer modeling could come up with something a "little more user friendly", while still keeping your basic design.

One variable I saw on your design was the feed line length.

The computer can tell us what are the best lengths of feedline in a short period of time.

[n3lrx]

The problem is RF is a "Theory" computers think of things "Literately" Not what if? But if, then. You can't exercise the good old imagination with a computer. It just doesn't happen that way. The software is only going to do what the programmer told it to do, nothing more. Computers (currently) cannot think for themselves. They're getting close, but not quite there yet. You have to throw some wire in the air and experiment, who knows it might defy your computer software. That's why I'd trust the word of someone who tried it over someone who just modeled it on a computer.

[ka7niq]

The problem is RF is a "Theory" computers think of things "Literately" Not what if? But if, then. You can't exercise the good old imagination with a computer. It just doesn't happen that way. The software is only going to do what the programmer told it to do, nothing more. Computers (currently) cannot think for themselves. They're getting close, but not quite there yet. You have to throw some wire in the air and experiment, who knows it might defy your computer software. That's why I'd trust the word of someone who tried it over someone who just modeled it on a computer.

Here is an example of a W5GI "Mystery" antenna, that is claimed to "confound computer modeling"
This is because Computer modeling has revealed it to be the poor antenna that it is.
There is no "Mystery" here, Computer Modeling clearly shows what is going on.
The only "Mystery" is why people even consider it, when there are so many other antennas that actually work as claimed, to be had.

The Computer is an awesome design too, for people (not me), who know what they are doing with it.

I don't have computer modeling software, nor do I know how to use it, so I started this thread http://forums.qrz.com/showthread.php?414706-Anyone-Care-To-Model-this-Simple-Antenna&p=3020488#post3020488

I am curious what Modeling has to say about this antenna

[KB2WIG]

How does modeling work with my 160m Isotron??


klc

I'm thinking of putting it on my Ford Explorer.

[ka7niq]

How does modeling work with my 160m Isotron??


klc

I'm thinking of puttig it on my Ford Explorer.

http://www.w8ji.com/e-h_antenna.htm

[K1JJ]

About antenna modelling:

Back in the 80's I put up my first 150' tower with 4 cleared acres and acquired an 18,000'  roll of #5 copper clad aluminium wire for $100.  This was JUST before computer modelling was mainstream.

I tried every antenna known to man for 75M, 40M and 20M -  vertical arrays, wire logs, wire Yagis, V beams, loops, Lazy H's, Sterba curtains, rhombics, stacked dipoles, etc. My main goal was a big signal into Europe, the USA and locally on AM for 75M.  I went thru ALL 18,000' of wire experimenting over two years.

What I found was for local work, a simple dipole at about 1/4 to 3/8 wavelength above ground was best.

For DXing, a Yagi worked great.  For real animal gain, then a combination of Lazy H's or Sterba curtains with parasitic reflectors was tops.

Stacked Yagis were always good too.


Now here's the point:   Later I got Mini Nec  and much later, EZNec V5.0 computer modelling programs. (MiniNec 1988)  I would have saved hundreds of hours of real whirl experimenting if I had used the modelling earlier. I tried antennas that were obviously too low to the ground for low angle performance - and many that were phased incorrectly. The modelling would have told me all this. And modelling would have optimized my designs instead of climbing and pruning for days.

A recent experience, 2013:  I wanted to put up a more effective local antenna for 75M AM for use out to maybe 300 miles.  I decided to try a 300' horizontal  dipole flat top at 90' fed with open wire. It modelled out to have maybe 2.5dBd gain at 60 degrees takeoff angle over my exisiting  1/2 wave dipole at 60'.  A no brainer to effectively double my signal strength locally.

But guess what?  I assumed there would be no interaction to my other antennas. It was to be erected in the clear, away from the other antennas. But before starting the project I decided to model all the other antennas in the field to make sure there were no pattern distortions. Turns out no matter where I put this big 300' wire on 4 acres, it did some damage to my other antenna patterns.  The worst was the high 75M 2 el loops for 75M.  The 300' wire caused the loops to lose most of their 5dBd gain and develop a hole for European coverage. The loops in turn negatively effected the 300' wire causing any local gain to be eliminated.

Looking at a bird's eye drawing of the antennas on paper looked fine, but the modelling showed it as a disaster. Years ago I would have certainly put this up and wondered for days why I wasn't seeing the old performance - or worse, never realizing what happened to my gains.

So, modelling, if used as a tool to verify and confirm ideas, can be a valuable tool for a ham. It can also be a good educational tool of what to expect from the many, many antenna designs out there to better tailor them for the best fit to our QTH and performance goals.

EZNec V. 5.0 for Windows is what I currently use and it can be mastered in a few days. It can be downloaded and tried free for 30 days.

http://www.eznec.com/


Tom, K1JJ

[KA0HCP]

Are you implying models aren't accurate?  GIGO.  There is no reason the Isotron can't be accurately modeled.

How does modeling work with my 160m Isotron??


klc

I'm thinking of puttig it on my Ford Explorer.

[ka7niq]

Are you implying models aren't accurate?  GIGO.  There is no reason the Isotron can't be accurately modeled.

How does modeling work with my 160m Isotron??


klc

I'm thinking of puttig it on my Ford Explorer.

Correct me if I am wrong, but has not modeling of the Isotrons and Tak Tenna's, etc, etc shown them to be, what they really are ?
I think I read somewhere that all these devices really are are deliberately unbalanced loads, designed to make the feed lines radiate.

[KB2WIG]

" Correct me if I am wrong, but has not modeling of the Isotrons and Tak Tenna's, etc, etc shown them to be, what they really are ? "

No, the modeling doesn't even approach the true usefulness; they make excellent bird perches.... ..


klc

[ka7niq]

" Correct me if I am wrong, but has not modeling of the Isotrons and Tak Tenna's, etc, etc shown them to be, what they really are ? "

No, the modeling doesn't even approach the true usefulness; they make excellent bird perches.... ..


klc

Tak Tenna's make excellent BBQ !

[n3lrx]

About antenna modelling:
..snip..
EZNec V 5.0 for Windows is what I currently use and can be mastered in a few days. It can be downloaded and tried free for 30 days.

http://www.eznec.com/

..snip..

There's also nec2c (Command line) and xnec2c (GUI) for Linux. Both are free. I am the lead packager for the Fedora Linux Amateur Radio SIG. I know both are in Fedora, because xnec2c requires nec2c, and for other distros the source can be found HERE

I have never had any luck figuring it out.

[The Slab Bacon]

I have only been a Ham for around 25 years, not nearly as long as many of you.
I agree with you that computer modeling has taken a lot of the good old fashioned fun out of just going out, and actually building something, then seeing how it actually works, on the air!

However, that being said, I still think computer modeling does have a place, in the overall scheme of things.

Hell, I remember back in the old days, when we made Yagi's, we simply cut the reflectors and directors about 5% shorter then the driven elements, spaced the elements evenly across the boom, and went out hunting DX.

Yes, these antennas "worked", and some worked real well.
However, they would be no match for the computer optimized Yagi's of today.

Same with your antenna.

It seems you have a great design, from what all the guys here have said.
Now, what IF that great design you have come up with, could be made even better, by computer modeling.

What IF computer modeling could come up with something a "little more user friendly", while still keeping your basic design.

One variable I saw on your design was the feed line length.

The computer can tell us what are the best lengths of feedline in a short period of time.

Well............. You have been a ham for 25 years, Hmmmm..........
Seems like you have spent most of those years modeling antennas and not building them. If you took the time you spent modeling antennas and used it to build a few of them, you might actually be on the air instead of arguing about it on a forum    

Keep in mind that antenna modeling software only knows what was programmed into it at the time that it was written. It can't figger out new scenarios on it's own, it can only compare the info that it is given to what was written into it. If you ask it to analize a scenario that was not written into it it cannot possibly give you an accurate answer.

Antenna discussions here are always a big source of pissing and moaning. Then when I throw my antenna into the mix, most of the computer modelers swear that it can't possibly work. Well.........I don't like being piss-weak, so I put out a pretty serious signal with my antenna that can't work. If you doubt me, you can ask any of the major players on the east coast!

Even a wet-string dipole works way better than no antenna at all! ! !  Get up off of your modeling program and trying to create the perfect world, put some wire up in the air and get on the air.

That's it, short, sweet, and simple. Nuff said! ! ! that is the end of this discussion for me! As Murphy said: "Never argue with a fool, sooner or later no one will be able to tell the difference"! ! !

Frank
AKA  KB3AHE

10-4, over and out!

[n3lrx]

Antenna discussions here are always a big source of pissing and moaning. Then when I throw my antenna into the mix, most of the computer modelers swear that it can't possibly work. Well.........I don't like being piss-weak, so I put out a pretty serious signal with my antenna that can't work. If you doubt me, you can ask any of the major players on the east coast!

I can vouch for that, I've heard Franks signal, as well as operated his station. If he can hear it, he can work it. With an antenna that doesn't work.

[ka7niq]

I have only been a Ham for around 25 years, not nearly as long as many of you.
I agree with you that computer modeling has taken a lot of the good old fashioned fun out of just going out, and actually building something, then seeing how it actually works, on the air!

However, that being said, I still think computer modeling does have a place, in the overall scheme of things.

Hell, I remember back in the old days, when we made Yagi's, we simply cut the reflectors and directors about 5% shorter then the driven elements, spaced the elements evenly across the boom, and went out hunting DX.

Yes, these antennas "worked", and some worked real well.
However, they would be no match for the computer optimized Yagi's of today.

Same with your antenna.

It seems you have a great design, from what all the guys here have said.
Now, what IF that great design you have come up with, could be made even better, by computer modeling.

What IF computer modeling could come up with something a "little more user friendly", while still keeping your basic design.

One variable I saw on your design was the feed line length.

The computer can tell us what are the best lengths of feedline in a short period of time.

Well............. You have been a ham for 25 years, Hmmmm..........
Seems like you have spent most of those years modeling antennas and not building them. If you took the time you spent modeling antennas and used it to build a few of them, you might actually be on the air instead of arguing about it on a forum    

Keep in mind that antenna modeling software only knows what was programmed into it at the time that it was written. It can't figger out new scenarios on it's own, it can only compare the info that it is given to what was written into it. If you ask it to analize a scenario that was not written into it it cannot possibly give you an accurate answer.

Antenna discussions here are always a big source of pissing and moaning. Then when I throw my antenna into the mix, most of the computer modelers swear that it can't possibly work. Well.........I don't like being piss-weak, so I put out a pretty serious signal with my antenna that can't work. If you doubt me, you can ask any of the major players on the east coast!

Even a wet-string dipole works way better than no antenna at all! ! !  Get up off of your modeling program and trying to create the perfect world, put some wire up in the air and get on the air.

That's it, short, sweet, and simple. Nuff said! ! ! that is the end of this discussion for me! As Murphy said: "Never argue with a fool, sooner or later no one will be able to tell the difference"! ! !

Frank
AKA  KB3AHE

10-4, over and out!

Frank, no one is "arguing" with you, so please don't get defensive.
Several here have said you put out a great signal with the antenna, and I am trying to figure out WHY you do.

[ka7niq]

Antenna discussions here are always a big source of pissing and moaning. Then when I throw my antenna into the mix, most of the computer modelers swear that it can't possibly work. Well.........I don't like being piss-weak, so I put out a pretty serious signal with my antenna that can't work. If you doubt me, you can ask any of the major players on the east coast!

I can vouch for that, I've heard Franks signal, as well as operated his station. If he can hear it, he can work it. With an antenna that doesn't work.

With absolutely NO disrespect intended or Implied towards Frank, or his Antenna, for the life of me, I can't understand how this can be possible.

Steve, G3TXQ, is a well known antenna/computer modeling expert, the designer of the K4KIO Hex Beam, and a regular on QRZ.

Here is what he found, when I posted the schematic of it, and asked for someone to computer model it -

 "What do you need to know?

Radiation patterns and extreme impedance variations very similar to a simple 60ft doublet!

Fed with 100ft of Wireman 551: 6dB feedline loss on 80m and 19dB loss on 160m. Losses would be less with some open-wire line formed from large diameter wire.

Steve G3TXQ


I have a very very small lot, and could really use a smallish, easy to build antenna, like this one!

[K1JJ]

I think the idea behind Frank's antenna is to minimize feedline losses by using homebrew very heavy gauge openwire feedline and a tuner using 3/8" copper tubing and strapping connections throughout.

A dream version of his antenna would be to have the amplifier mounted up at the center of the antenna and the final pi-network directly coupled to his low impedance antenna. In this case, I bet his short dipole would be within two dB of a full size dipole on 75M.  

And, if the antenna conductors themselves were of sufficient diameter, there would be little loss compared to a full size dipole.  So if we can minimize the tuner/feedline losses thru heavy conductors, we are almost there.

Theoretically, we could use a 75M dipole that is only one foot long made of superconductors that exhibits close to zero ohms. This would work as well as a full size dipole. Just imagine a 3el 75M Yagi that you could hold in your hand.  The radiation pattern would look the same as a full size antenna.

Bottom line is it's all about how much we control the losses when we shrink down antennas below full size.  Since superconductors are not yet practical, brute conductor thickness is what we have to work with.


T