best 11meter vertical ever, period.

[crusader]

forget a-99 I-10K i-max2000 and all that.the only antenna i have ever owned that out performed every other vertical was the avanti sigma 4, a massive 3/4 wave monster with gamma match and low low swr between 25.5MHz - 28.0MHz rated at 2KW input i preferred using this one over the 3 element yagi. a copy is still sold in the uk under the name sirio vector 4000 but how good a copy i dont know. the sigma used with 70 watts cut through the pile ups on 11meters back in the early to late eighties when ssb was crammed. would love to hear from others who remember this great antenna!!

 

[bob85]

i still have the original avanti and several sirio vector 4000's, i have been using them for over 20 years, on performance the vector beats the avanti when they are set up correctly ( houres of moving tapping point and retuning for best signal at distance ) but they are way too flimsy to use even in moderate 60mph winds they will break, the avanti was made from infinately better material which with a doubleskinned bottom section withstood 110mph winds that snapped my guys and brought the whole lot down back in the mid eighties, so i hybridised the two to make a 4 legged unit using the avanti vertical extended to 32 feet which lasted a good few years up to the last 90+mph winds when the basket collapsed, another fantastic antenna i had was the ham international big mack, http://pageperso.aol.fr/daviken/Antennes/Antennes.htm, it outperformed my avanti and would at least equal the hybrid but it too was not really strong enough for our weather, so we cannot forget the i10k, its probably the best performing rugged antenna you can buy today and unlike the avanti and sirio theres no need to spend houres playing with the tuning to get the best signal from it as jay did all that before he marketed the antenna, i have played with mine i just cant stop myself and there seems to be no improvement to be had, you can just follow jays tuning instructions and they work extremely well out the box, its the best of the many 5/8 i ever owned and look unlikely to break in severe weather, if it does break in the wind as opposed to human dammage then i am sure jay will come up with a solution because thats just the way he is, mr avanti, sirio, ham international would never do that, you cant call them up and get advice and they definately did not optimise their product before it hit the market.

 

[FL Native]

i still have the original avanti and several sirio vector 4000's, i have been using them for over 20 years, on performance the vector beats the avanti when they are set up correctly ( houres of moving tapping point and retuning for best signal at distance ) but they are way too flimsy to use even in moderate 60mph winds they will break, the avanti was made from infinately better material which with a doubleskinned bottom section withstood 110mph winds that snapped my guys and brought the whole lot down back in the mid eighties, so i hybridised the two to make a 4 legged unit using the avanti vertical extended to 32 feet which lasted a good few years up to the last 90+mph winds when the basket collapsed, another fantastic antenna i had was the ham international big mack, http://pageperso.aol.fr/daviken/Antennes/Antennes.htm, it outperformed my avanti and would at least equal the hybrid but it too was not really strong enough for our weather, so we cannot forget the i10k, its probably the best performing rugged antenna you can buy today and unlike the avanti and sirio theres no need to spend houres playing with the tuning to get the best signal from it as jay did all that before he marketed the antenna, i have played with mine i just cant stop myself and there seems to be no improvement to be had, you can just follow jays tuning instructions and they work extremely well out the box, its the best of the many 5/8 i ever owned and look unlikely to break in severe weather, if it does break in the wind as opposed to human dammage then i am sure jay will come up with a solution because thats just the way he is, mr avanti, sirio, ham international would never do that, you cant call them up and get advice and they definately did not optimise their product before it hit the market.

here you go i fixed the link

pageperso.aol.fr/daviken/Antennes/Antennes.htm

 

[crusader]

avanti wind damage

hey bob you reminded me of the time my sigma iv got shortened by about two sections during a storm, found the pieces about forty feet away in a neighbours garden, the vswr before repair was only about 1:1.6 so was still perfectly usable.was always hard to work on this antenna in a small garden, could not lay it down because of the cage at the bottom, i am sweating just thinking about it!!

 

[Master Chief]

OK, but I will make this brief...

The Sigma IV was (is) a great antenna! To this day, I love the way they look! While PHYSICALLY 3/4 of a wave length long, electrically it is nothing more than a 1/2 wave antenna.

To quote one of the engineers who worked for Avanti;

Although the antenna is 3/4 wave tall- the bottom quarter does not radiate. It serves as a matching section between the hi end impedance of the half wave radiator and zero ohms at the base. The feed then is tapped up to the 50 Ohm point and the gamma cancels the inductive reactance of the tapping rod. This antenna is electrically equivalent to the popular J poles so commonly seen on VHF/UHF.

So there you have it. The Sigma IV is a real neat 1/2 wave antenna. My experience is that the Sigma 5/8 wave performed better than my Sigma IV. Your mileage may vary.

I will test the Sigma IV against the Sigma 5/8 and the I-10K someday. I fully expect the I-10K to soundly beat the other two as my personal experience with all three has already proven.

 

[Captain Kilowatt]

I have to agree with the 1/2 wave part.Most people just look at the PHYSICAL dimensions and ignore the ELECTRICAL dimensions.I'll bet 95% of the people think a J-pole is a 3/4 wave antenna when in fact it is an end fed 1/2 wave antenna.I still think the Sigma IV would beat most other 1/2 wave antennas like the A99 and similar because it has lower losses in the matching system.

 

[Master Chief]

I still think the Sigma IV would beat most other 1/2 wave antennas like the A99 and similar because it has lower losses in the matching system.

I would have to agree although I haven't tested the feedpoints of the two antennas you list.

A comment about the gamma match, and this goes for any gamma match; they are lossy. There is really no way to get around it. Sure they work, but a beta match scheme (hairpin) has less loss than a gamma and therefore gets more signal into the antenna. Maybe this is why most of the ham antennas use this type of feed point.

I'm sure this is why Jay is using it on his Crusader beams.

Heck, even Cushcraft isn't using gamma matches much anymore. Maco will because they are cheap to build and work, but there is a better way!

 

[freecell]

end-fed 1/2 wave verticals don't require ground plane radials for efficient operation. so if there is no radiation from the bottom 1/4 wave length of the antenna, what the hell are the 1/4 wave radials for? never mind the fact that in no less than two instances in the patent application the inventor speaks of the entire 3/4 wavelength as "the radiating element." there is no radial system in a j-pole design. your comparison of the Sigma 4 to a j-pole is an unsubstantiated opinion and your mystery engineers comment is just as suspect. put a few watts into the antenna and use a field strength meter anywhere in the area of the bottom 1/4 wavelength and tell me again how there is no radiation.

 

[Master Chief]

end-fed 1/2 wave verticals don't require ground plane radials for efficient operation.so if there is no radiation from the bottom 1/4 wave length of the antenna, what the hell are the 1/4 wave radials for?

Ground plane radials? Where? Those aren't ground plane radials as this antenna is not a ground plane antenna. You know that.

never mind the fact that in no less than two instances in the patent application the inventor speaks of the entire 3/4 wavelength as "the radiating element."

Not going to argue that point again.

there is no radial system in a j-pole design.

See, we can agree on something!

your comparison of the Sigma 4 to a j-pole is an unsubstantiated opinion and your mystery engineers comment is just as suspect.

No it isn't. Look at it! Tell me you don't see similarities. In a previous thread you even conceeded to that fact. Send me your info and I will put you in touch with both engineers, as I have offered to you in the past.

put a few watts into the antenna and use a field strength meter anywhere in the area of the bottom 1/4 wavelength and tell me again how there is no radiation.

Put a few watts into a J-pole and tell me you don't see the same thing. Can we agree that the bottom 1/4 wave section of the J-Pole is a matching section? Are all those other engineers wrong? Could we also conclude that the Sigma IV uses the same principal, not to mention that I quoted one of Avanti's engineers as it is.

If it looks like a duck, and talks like a duck.....

What I won't do is argue about this again. If I'm wrong, you need to prove me wrong. Saying disparaging things about me does not prove your point. You are a smart man, model it and let's see what that says. When I'm ready to test the antennas, I will invite you out to the California desert so we can all see the truth together.

As for me, I have no reason to argue this fact with you further on here.

 

[228]

"Ground plane radials? Where? Those aren't ground plane radials as this antenna is not a ground plane antenna. You know that."

you'd better read it again.

http://www.firecommunications.com/patents/sigma4/

the 3 upwardly flaring, base mounted 1/4 wave conductors form the ground plane / counterpoise for the bottom 1/4 wave portion of the vertical element. the reason for sweeping the radial elements in the upward direction was to reduce the amount of lateral or horizontal space required for mounting and to minimize the deleterious effects in the surrounding environment such as "buildings, guy wires and other interfering masses."

for anyone sufficiently motivated to get up off their posterior and make the necessary field strength measurements it's all too obvious that the bottom 1/4 wavelength of the vertical radiator is definitely producing pronounced levels of radiated signal.

i don't need to relocate myself from one desert to another to "see" any truth. take a field strength meter up to the base of the antenna and "see" the truth for yourself.

 

[Master Chief]

I don't have to. I have a copy of the patent and have read it. I think a re-visit to what constitutes a "ground plane" is in order.

Maybe you can explain how 3 "diverging elements" shorted at the end constitutes a ground plane.

I'm always willing to learn.

 

[228]

"I don't have to. I have a copy of the patent and have read it. I think a re-visit to what constitutes a "ground plane" is in order."

i suggest you read it several more times.

"Maybe you can explain how 3 "diverging elements" shorted at the end constitutes a ground plane."

the same way the ground plane in the body of a vehicle or a solid cone shape would replace the 3 diverging elements in the Sigma 4. i already understand what constitutes a ground plane or counterpoise "mass." whether it's formed by skeleton elements or continuous sheet metal it's still a ground plane.

"I'm always willing to learn."

then make the field measurements at the base of the Sigma 4 and quit parroting everything you hear without checking it out for yourself. take an ordinary ground plane antenna and a piece of wire and connect the far ends of the radial elements together as you arrange the wire around the perimeter. now go learn something.

 

[Master Chief]

then make the field measurements at the base of the Sigma 4 and quit parroting everything you hear without checking it out for yourself. take an ordinary ground plane antenna and a piece of wire and connect the far ends of the radial elements together as you arrange the wire around the perimeter. now go learn something.

I've done that. But the 3 elements on a Sigma IV is not a ground plane. We can't get any further until we can agree on this.

However;

I can take one of my I-10Ks and interconnect the end of the radials. Of course this effectivley loads the ends and I would have to shorten the actual radials. But why would we want to do that? We all know there is nothing better than full size elements. In this case, those elements ARE a ground plane; in the Sigma IV, they are not.

I'm not parroting. I was the first one to ever challenge the misconception that the Sigma IV is a 3/4 wave antenna. Just because you don't believe it doesn't mean I'm wrong.

Please find the part in the patent that states the 3 diverging elements are part of a ground plane. The Sigma IV is NOT a ground plane antenna.

It is a fantastic antenna though! Sure wish it worked better though.

 

[228]

"But the 3 elements on a Sigma IV is not a ground plane. We can't get any further until we can agree on this."

no, YOU can't get any further until i'm as wrong as you are.
why would i agree with you on that point when you're wrong?

so what you're telling me is that we both have to be wrong before you're willing to continue the discussion. now tell me again about how willing you are to learn. if we're both wrong then what's to learn?

the three, upwardly swept 1/4 wave conductors in the Sigma 4 comprise a ground plane and when you can think and analyze in at least three dimensions you'll come to realize it.

it makes no sense whatsoever for me to agree to be as wrong as you are just so that we can continue this insanely stupid thread. you tell me exactly why it's not possible and then i'll tell you just exactly why it is. if you have actually read anything in the patent you would already realize that you're in a no-win situation.

 

[freecell]

not to correct 228 but in addition, you can actually perceive this 2 dimensionally and i can demonstrate this way.

when we saw the 3 1/4 wavelength downward elements on the starduster that was a ground plane. when we saw the 3 or 4 1/4 wavelength elements at 90 degrees to the radiating element on a 5/8 or whatever that was a ground plane. when we see the same 3 or 4 1/4 wave elements swept upwards, all of a sudden that's not a ground plane anymore.