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Avanti Sigma4: An alternative view point
- Thread starter bob85
- Start date
sigma iv
I haven't seen such controversy over an antenna design, but the signa iv/
nv 4000 etc should be good performers. how they work is spelled out in
the beginning of this thread. that is, a sleeve antenna. in particular the 3 to
1 length of central monopole to the sleeves version. where the sleeves are
1/4 wave and resonate. And radiate constructively with the top 1/2 portion.
I haven't seen such controversy over an antenna design, but the signa iv/
nv 4000 etc should be good performers. how they work is spelled out in
the beginning of this thread. that is, a sleeve antenna. in particular the 3 to
1 length of central monopole to the sleeves version. where the sleeves are
1/4 wave and resonate. And radiate constructively with the top 1/2 portion.
That is something I try to avoid.
Having sold quite some antennas myself, and having heard the reflections users have.
(in comparisment to others....) It seems that often the "new" user is in favour of the "new" antenna.
Of course there are situations where the new antenna is actually better but besides the technical fact.
You know there are those in large numbers, who just tell it is better without having a clue...
Anyone who is honest knows, some claims made by users just cant be true.
I tend to believe:
There are a few things beeing the cause of this.
From a electrical point of view:
The comparisment is made to an "old" antenna
The comparisment is made to an older smaller antenna.
Often the old antenna had "old" coax...
The old antenna was at a lower location.
etc.
From a "attitude" point of view:
Often the new antenna is more expensive....so it must be better
Often the new antenna must be better cause the user is using it.
Often the new antenna must be better cause everybody says so.
Ask 10 users of te Imax ...what they think of the antenna.
Would you have the same mindset ?
Ask 10 people what the best car is they have driven.
You will end up with many different answers, often "the best" beeing something in a "mercedes" direction.
But what if you could use a Ferrari ?
People not always know what is best...they tend to think what they have is best.
Im afraid the majority of users isnt capable of providing an honest indication.
There are only few who really test antennas with a open mind.
Kind regards,
Henry
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I think we should be mindful that the same inconsistencies are likely to be present when one gives a negative review. In fact, from reading this thread we know some are. Such as testing while another resonant antenna is nearby.
On the other hand when someone can describe the exact performance characteristics to a "T" and has reproduced the same results in the field that you can regularly, you gain faith in their reports.
For example, when someone reports they couldn't tell the difference between antenna performance at 20 miles but at 50 miles it begin to "shine". I know their measurements were accurate enough to spot the exact area the antenna excels in.
In the absence of trying something yourself can you think of any better way for the average operator to get a sense of its performance other then reading the reviews of actual users? I do this with just about every purchase I make from printers to cars and find it puts me in a better position as an educated buyer.
Had I started using things like Angie's list and QRZ reviews for the electronics years ago, I would have avoided several disappointing purchases. At the same time we have to realize when something sounds too good to be true, it probably is not. For example never expect the S4 to outperform a multi element beam. If it does, the beam was not assembled correctly.
On the other hand when someone can describe the exact performance characteristics to a "T" and has reproduced the same results in the field that you can regularly, you gain faith in their reports.
For example, when someone reports they couldn't tell the difference between antenna performance at 20 miles but at 50 miles it begin to "shine". I know their measurements were accurate enough to spot the exact area the antenna excels in.
In the absence of trying something yourself can you think of any better way for the average operator to get a sense of its performance other then reading the reviews of actual users? I do this with just about every purchase I make from printers to cars and find it puts me in a better position as an educated buyer.
Had I started using things like Angie's list and QRZ reviews for the electronics years ago, I would have avoided several disappointing purchases. At the same time we have to realize when something sounds too good to be true, it probably is not. For example never expect the S4 to outperform a multi element beam. If it does, the beam was not assembled correctly.
Shockwave,
Im not pussing m8....as clearly as soon as i receive them it will take a large amount of time to respond
It just crossed my mind i never had the info.
any updates ?
Kind regards,
H.
Im not pussing m8....as clearly as soon as i receive them it will take a large amount of time to respond
It just crossed my mind i never had the info.
any updates ?
Kind regards,
H.
Hello Henry,
I did find the collinear antenna in the storage unit but unfortunately it got beat up pretty bad after I lost interest in it. The working prototype only succeeds in adding an additional in phase 1/2 wave to the existing 3/4 wave and falls short of adding 3db as a result. The last phasing coil I used was literally taped across the insulator and fell off over the years. I found it flat underneath a pallet of boxes!
I thought I could just measure that coil but then I found the alligator clip and short wire that I used to tap the coil in the spot that produced the best gain. Needless to say that tap point was lost. What is not lost is my memory of how it works or ability to explain it in a way that is reproducible. Although, I am surprised that I've not been able to get anyone to build a model as I described.
It really is very simple. Take a stock Sigma or Vector model in EZNEC. Imagine we attach a 2 or 3 inch insulator right at the top of this antenna. Add one horizontal wire extending to the left from the bottom of the insulator that connects to the top of the existing antenna. According to EZNEC this wire should be about 1/4 wavelength or just over 8 feet on this band.
At the far open left end of this new horizontal 1/4 wave wire, connect a second upward, vertical wire the same length as the 2 or 3 inch insulator. From the top of this short vertical wire connect a 3rd wire that is horizontal, extending to the right and parallel to the first horizontal 1/4 wave wire you added. The open end should now be inline with the top of the insulator. You have just formed a 1/4 wave shorted phasing stub. The overall phase shift through both legs of this stub will be delayed 180 degrees.
From the top of this insulator connect a 1/2 wave vertical wire to the top of the phasing stub to form the top 1/2 wave collinear element. Run the average gain test. With a little tweaking of both vertical radiator lengths and the phasing stub you might see a maximum of 1.5 or 1.7db over the stock antenna in this program.
Now we need to test these model results in the field. The easiest way to do that is to let EZNEC rescale the antenna for 2 meters then build it. The antenna will tune up and work fine before you add the insulator, phasing stub and top 1/2 wave. As soon as you do that the reactance and match go out the window. Lots of retuning the gamma can bring the VSWR down but there is no gain over the stock antenna and some loss could be detected through the match.
Just before you give up on getting this to work in the field do something crazy. Eyeball the length of the phasing stub to find the mid point and cut it right in half! Then attach the small shorting bar back across the open end of the stub and watch the antenna start to work in the field. You'll also notice that you can remove the entire top of the antenna from the stub up and not upset the match. Exactly how we expect a properly tuned collinear to operate.
This collinear antenna only needs a 90 degree phase delay since the first 1/4 wave driven from the feedpoint has already been confined inside the cone and effectively "delayed" within it. Remember a phasing section on a collinear antenna merely has to provide a means of minimizing radiation at a key point on these longer antennas were the currents become deconstructive. That condition exists inside the cone. It doesn't have to look conventional to the eye and can be rather "non apparent" as in this case.
If the outside or 3rd conductor on the cone was not radiating a significant in phase current, what EZNEC predicts about the 180 degree phase delay would still work in the field. The fact that the only phase delay that can make another 1/2 wave fall into phase with the radiation below it is a 90 degree shift, proves there is another significant in phase current other than the original 1/2 wave extending above the cone. It also supports that the wavelength of that second radiated current must be the 90 degree 1/4 wave outside surface of the cone.
Funny thing is if you now take what you learned in the field and apply it in EZNEC with the working 90 degree phase delay, you find the EZNEC results here will be just as messed up as the program results proved to be in the field. All of this together supports my conclusion that no EZNEC model has ever displayed an accurate analysis of the Sigma design. I've presented this information everywhere from forums to Roy who wrote the EZNEC programs. Roy told me the program was not capable of miscalculating any radiation currents and that the error must be in my phase delay measurements.
To me that translated into "I don't know and I don't care" because it's a slim chance that I failed to take the measurements from his software and miss them on the tape measure by making them 100% longer. It's an insult to suggest that one can't tell 4 feet from 8 feet on the Stanley or read the numbers printed on the software screen. Many of you have probably seen me rant about all of this before and I apologize for being redundant, but at the same time there are people here interested in why the common model can't show what field tests and CST do.
Admittedly, the time I could invest in this research hinged on the profitability of the project. Because the results proved the antenna was an in phase 3/4 wave radiator, adding another single collinear section could never double the existing gain. One night I found myself going over the list of improvements required on the prototypes before they could go into production. We were dealing with everything from reduced bandwidth and power handling to weather detuning the phasing stub and wind casing undesired mechanical beam tilt on the long antenna.
All that work and added expenses to manufacture something of commercial grade and for a measly 1.5db? It was clear the most effective and economical way to add gain here was to add more antennas mounted and fed in phase. That's how you get close to the full 3db gain every time you double the number of antennas and has been a proven method for over half a century.
I did find the collinear antenna in the storage unit but unfortunately it got beat up pretty bad after I lost interest in it. The working prototype only succeeds in adding an additional in phase 1/2 wave to the existing 3/4 wave and falls short of adding 3db as a result. The last phasing coil I used was literally taped across the insulator and fell off over the years. I found it flat underneath a pallet of boxes!
I thought I could just measure that coil but then I found the alligator clip and short wire that I used to tap the coil in the spot that produced the best gain. Needless to say that tap point was lost. What is not lost is my memory of how it works or ability to explain it in a way that is reproducible. Although, I am surprised that I've not been able to get anyone to build a model as I described.
It really is very simple. Take a stock Sigma or Vector model in EZNEC. Imagine we attach a 2 or 3 inch insulator right at the top of this antenna. Add one horizontal wire extending to the left from the bottom of the insulator that connects to the top of the existing antenna. According to EZNEC this wire should be about 1/4 wavelength or just over 8 feet on this band.
At the far open left end of this new horizontal 1/4 wave wire, connect a second upward, vertical wire the same length as the 2 or 3 inch insulator. From the top of this short vertical wire connect a 3rd wire that is horizontal, extending to the right and parallel to the first horizontal 1/4 wave wire you added. The open end should now be inline with the top of the insulator. You have just formed a 1/4 wave shorted phasing stub. The overall phase shift through both legs of this stub will be delayed 180 degrees.
From the top of this insulator connect a 1/2 wave vertical wire to the top of the phasing stub to form the top 1/2 wave collinear element. Run the average gain test. With a little tweaking of both vertical radiator lengths and the phasing stub you might see a maximum of 1.5 or 1.7db over the stock antenna in this program.
Now we need to test these model results in the field. The easiest way to do that is to let EZNEC rescale the antenna for 2 meters then build it. The antenna will tune up and work fine before you add the insulator, phasing stub and top 1/2 wave. As soon as you do that the reactance and match go out the window. Lots of retuning the gamma can bring the VSWR down but there is no gain over the stock antenna and some loss could be detected through the match.
Just before you give up on getting this to work in the field do something crazy. Eyeball the length of the phasing stub to find the mid point and cut it right in half! Then attach the small shorting bar back across the open end of the stub and watch the antenna start to work in the field. You'll also notice that you can remove the entire top of the antenna from the stub up and not upset the match. Exactly how we expect a properly tuned collinear to operate.
This collinear antenna only needs a 90 degree phase delay since the first 1/4 wave driven from the feedpoint has already been confined inside the cone and effectively "delayed" within it. Remember a phasing section on a collinear antenna merely has to provide a means of minimizing radiation at a key point on these longer antennas were the currents become deconstructive. That condition exists inside the cone. It doesn't have to look conventional to the eye and can be rather "non apparent" as in this case.
If the outside or 3rd conductor on the cone was not radiating a significant in phase current, what EZNEC predicts about the 180 degree phase delay would still work in the field. The fact that the only phase delay that can make another 1/2 wave fall into phase with the radiation below it is a 90 degree shift, proves there is another significant in phase current other than the original 1/2 wave extending above the cone. It also supports that the wavelength of that second radiated current must be the 90 degree 1/4 wave outside surface of the cone.
Funny thing is if you now take what you learned in the field and apply it in EZNEC with the working 90 degree phase delay, you find the EZNEC results here will be just as messed up as the program results proved to be in the field. All of this together supports my conclusion that no EZNEC model has ever displayed an accurate analysis of the Sigma design. I've presented this information everywhere from forums to Roy who wrote the EZNEC programs. Roy told me the program was not capable of miscalculating any radiation currents and that the error must be in my phase delay measurements.
To me that translated into "I don't know and I don't care" because it's a slim chance that I failed to take the measurements from his software and miss them on the tape measure by making them 100% longer. It's an insult to suggest that one can't tell 4 feet from 8 feet on the Stanley or read the numbers printed on the software screen. Many of you have probably seen me rant about all of this before and I apologize for being redundant, but at the same time there are people here interested in why the common model can't show what field tests and CST do.
Admittedly, the time I could invest in this research hinged on the profitability of the project. Because the results proved the antenna was an in phase 3/4 wave radiator, adding another single collinear section could never double the existing gain. One night I found myself going over the list of improvements required on the prototypes before they could go into production. We were dealing with everything from reduced bandwidth and power handling to weather detuning the phasing stub and wind casing undesired mechanical beam tilt on the long antenna.
All that work and added expenses to manufacture something of commercial grade and for a measly 1.5db? It was clear the most effective and economical way to add gain here was to add more antennas mounted and fed in phase. That's how you get close to the full 3db gain every time you double the number of antennas and has been a proven method for over half a century.
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Hello Shockwave,
My apologize for not beeing clear here.
I was refering to the exact dimensions of your dominator.
As you agreed to pass them towards me, so i can have a look at them.
Of course with the confirmation that I wont share them, and wont be using them for any commercial activites
Remember ?
Kind regards,
Henry
My apologize for not beeing clear here.
I was refering to the exact dimensions of your dominator.
As you agreed to pass them towards me, so i can have a look at them.
Of course with the confirmation that I wont share them, and wont be using them for any commercial activites
Remember ?
Kind regards,
Henry
Hello Shockwave,
Thank you for your fast and interesting answer !
It shouldnt be that difficult to give it a go...
Anyway, my apologize for not beeing clear here.
I was refering to the exact dimensions of your dominator.
As you agreed to pass them towards me, so i can have a look at them
Of course with the confirmation that I wont share them, and wont be using them for any commercial activites
Remember ?
Kind regards,
Henry
Thank you for your fast and interesting answer !
It shouldnt be that difficult to give it a go...
Anyway, my apologize for not beeing clear here.
I was refering to the exact dimensions of your dominator.
As you agreed to pass them towards me, so i can have a look at them
Of course with the confirmation that I wont share them, and wont be using them for any commercial activites
Remember ?
Kind regards,
Henry
Thank you for your respons shockwave.
But again, this wasnt what i was asking.
I'm not looking for a "rough" indication on the radiator length and radial length with wavelengths...
I need exact data: lengths / diameters / angles which bolts and screws etc.
The reason im asking:
Im trying to limited the amount of errors in comparisment to your "best" working version.
In case the outcome isnt what you would expect....im trying to avoid things like: "well, you havnt tested the V4K we found to be "best".
If the outcome is what you expect and does provide a clear insigth "it is better".
You have an independand source confirming it
Kind regards,
Henry
But again, this wasnt what i was asking.
I'm not looking for a "rough" indication on the radiator length and radial length with wavelengths...
I need exact data: lengths / diameters / angles which bolts and screws etc.
The reason im asking:
Im trying to limited the amount of errors in comparisment to your "best" working version.
In case the outcome isnt what you would expect....im trying to avoid things like: "well, you havnt tested the V4K we found to be "best".
If the outcome is what you expect and does provide a clear insigth "it is better".
You have an independand source confirming it
Kind regards,
Henry
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Had I been vague I could understand but element lengths given at .82 and .25 wavelength are precise and not approximations. You need not be anywhere near this accurate to spot the inconsistencies between the program and working prototypes. The differences here are measured in feet not fractions of an inch. I thought the goal here was to prove whether or not EZNEC was capable of modeling the design. Something that this 90 degree difference in phase suggests the models we have seen in the program are not able to display.
Not to be disrespectful to anyone's thoughts or ideas here but I'm well past the point of needing more independent confirmation of this antennas performance. It's been forwarded to me by engineers filing CP's from Alaska to Guam for years now. Some of these broadcast stations have had to jump through loopholes in order to clearly define their radiated field strength to insure they met new regulations regarding everything from downward radiation at the site to second adjacent channel protection.
Today the only question I have left regarding this design is why has every model ever produced other than the one done in CST, failed to show the antenna as the patent and field tests show, the "entire antenna radiates constructively"? That's the only open end in the debate whose cause has yet to be determined. Now it all boils down to either everyone has built the model wrong or the software is deficient. Sadly the one person best qualified to answer this question entered a state of denial by saying his program is not capable of such error and expressed no interest in identifying the obvious discrepancies.
Not to be disrespectful to anyone's thoughts or ideas here but I'm well past the point of needing more independent confirmation of this antennas performance. It's been forwarded to me by engineers filing CP's from Alaska to Guam for years now. Some of these broadcast stations have had to jump through loopholes in order to clearly define their radiated field strength to insure they met new regulations regarding everything from downward radiation at the site to second adjacent channel protection.
Today the only question I have left regarding this design is why has every model ever produced other than the one done in CST, failed to show the antenna as the patent and field tests show, the "entire antenna radiates constructively"? That's the only open end in the debate whose cause has yet to be determined. Now it all boils down to either everyone has built the model wrong or the software is deficient. Sadly the one person best qualified to answer this question entered a state of denial by saying his program is not capable of such error and expressed no interest in identifying the obvious discrepancies.
i can't get a straight answer from the necmen, i ask how eznec handles transmission-line currents but get no answer, i don't see them on the sigma or astroplane models, only one set of currents are displayed where are the transmission-line mode currents ??
we know transmission-lines in nec should be handled as a transmission-line yet we have folk modeling beta matched 1/4waves ignoring the beta should be handled as a transmission-line,
the beta or hairpin ect is not some bent bit of wire that makes up the extra length of the short radiator, its a transmission-line shorted at the far end with a defined electrical length and characteristic impedance,
if the source of radiation from the sleeve whatever the magnitude is due to transmission-line mode currents as stated in the arrl open sleeve article,
how can eznec include them when you don't model the sleeve as a transmission-line ?,
i do agree very much with henry,
few cbers are capable of doing a meaningfull test, we have videos of two antenna switch flickers that prove it all over youtube,
i also agree with the trend to convince yourself one antenna is superior especially if it costs more or is perceived by your peer groupe as superior,
i await the return of the mighty big-mac,
bob
we know transmission-lines in nec should be handled as a transmission-line yet we have folk modeling beta matched 1/4waves ignoring the beta should be handled as a transmission-line,
the beta or hairpin ect is not some bent bit of wire that makes up the extra length of the short radiator, its a transmission-line shorted at the far end with a defined electrical length and characteristic impedance,
if the source of radiation from the sleeve whatever the magnitude is due to transmission-line mode currents as stated in the arrl open sleeve article,
how can eznec include them when you don't model the sleeve as a transmission-line ?,
i do agree very much with henry,
few cbers are capable of doing a meaningfull test, we have videos of two antenna switch flickers that prove it all over youtube,
i also agree with the trend to convince yourself one antenna is superior especially if it costs more or is perceived by your peer groupe as superior,
i await the return of the mighty big-mac,
bob
Hello Shockwave,
I was just trying to illuminate errors for future reference.
I find it strange that you find those measurements precise.
You know element length is depending on diameter.
You know the angle of the radials are important.
etc.
However, opposite to what you have promissed me in the past...
I am not expecting anything anymore.
Thank you for your time.
Kind regards,
Henry
I was just trying to illuminate errors for future reference.
I find it strange that you find those measurements precise.
You know element length is depending on diameter.
You know the angle of the radials are important.
etc.
However, opposite to what you have promissed me in the past...
I am not expecting anything anymore.
Thank you for your time.
Kind regards,
Henry
I know nec2 uses one set of currents for its calculations. I know that nec2 can handle induced currents, as is apparent with its ability to model yagi antennas, but I'm not sure how it would handle induced currents on a wire that already has currents present. I would think it would add the currents on said wire but I am not sure, and it is possible that it doesn't factor in induced currents on said wires with an existing current at all. I have also attempted to model a hairpin match once, unsuccessfully.
That being said, when I visualize the fields of the Vector design, I don't think you need two separate currents on a single wire to explain what is happening. It is complicated to explain, but currents in the basket area would add up to create two separate combined fields, one outside the basket, and one inside. These fields would be 180 degrees out of phase with each other, and would have minimal if any effect on each other. The outside field would be in phase with the upper section of the antenna, and the inside field is in phase with the part of the vertical that is inside the basket area. This scenario would have an effect that matches the animated picture that shockwave has provided, and without the need for "transmission line mode currents". Nec would have just as much trouble modeling this scenario as it attempts to use currents in place of RF fields to calculate gain. As such, it has no concept that an entire RF field is contained within the basket area of the antenna.
When it comes to transmission line mode currents, every time they are applied when I visualize the fields in the 3d nearfield space around the antenna, no matter which antenna is being talked about, I see a similar effect as what people say it takes two currents to achieve made by a single current. That being said I could be wrong, and am still learning and thinking on the topic.
Anyway, that is my take on what is happening with the antenna in question. I don't claim to be an expert, especially when it comes to nec, but this antenna has spurred more thinking and study of theory on my part than any other antenna out there... Unfortunately what I'm seeing happening with RF fields from this antenna in its nearfield is difficult for me to explain.
The DB
Thank you for your respons shockwave.
But again, this wasnt what i was asking.
I'm not looking for a "rough" indication on the radiator length and radial length with wavelengths...
I need exact data: lengths / diameters / angles which bolts and screws etc.
The reason im asking:
Im trying to limited the amount of errors in comparisment to your "best" working version.
In case the outcome isnt what you would expect....im trying to avoid things like: "well, you havnt tested the V4K we found to be "best".
If the outcome is what you expect and does provide a clear insigth "it is better".
You have an independand source confirming it
Kind regards,
Henry
Henry, I didn't believe the agreement between you and Donald would ever happen back a long time ago...when the idea was originally discussed. Such a request might not even be necessary IMO. I also don't think Donald, rightfully so, wants to risk divulging the details to his Dominator...for the world to see.
Even if you fulfilled your side of this agreement between you two...what results could you publish that would not seem to violate the agreement.
Shockwave published the CST animated image for Sirio's New Vector 4K right here on WWDX. He also publishes the same image on his Website, and that is in support of his words describing his Dominator.
With Donald linking the NV4K to his Dominator on his own Website, it would seem to me your using Sirio's antenna would be good enough. Then if the gain, pattern, bandwidth, phase, and currents for the New Vector 4K model all worked out to agree or disagree with Donald's words...then you could publish all of your findings and not break a trust.
Henry, why don't you do what you planned to do using the NV4K instead of the Dominator? We have the Sirio image noted above, and Sirio has published some other detailed spec based on this image that you could compare.
Then you could publish everything for your new model, right down to the actual dimensions, and you would not violate Donald's interest in his Dominator, or the agreement between you two.
You could then change the length of the radiator to = Donald's Dominator length at .82% wavelength...and see if it made some difference.
You could keep that info to yourself and further fulfill the previous agreement.
How is that for a compromise?