best 11meter vertical ever, period.

[RoadWarrior]

I once owned a copy of the Sigma 4 back in
the 1980's. Good performimg antenna, but, high
winds broke the top section off twice, so, i
sold it to my friend who fixed it up.
He passed away, but, his kids still have the antenna
inside there attic. I'm going pick it up soon and
just for curiousity test it against my I-10K.

 

[freecell]

does your copy use the whip for the top section or the tubing element?

 

[bob85]

roadwarrier try making it 32feet long when you have tested it at 27 feet see what you think, i have owned and sold 5 original avantis both versions, a salut 27feet 3 legs, a commtell 444 27feet 4 legs which i smashed up in a rage when i bust a sepparator while errecting it at 73 feet after fixing the basket that had fallen appart in high wind, and 4 sirio vector 4000's the absolute weakest antenna out there but i still have all 4, only the real avantis had any stamina in our weather, all the 27 footers worked about the same.

 

[RoadWarrior]

I'll let you know about the tubing when i see it
again as i just can't remember. I know it was made
by sirio though.

 

[bob85]

freecell i dont doubt you on this you understand antennas better than i do and your ideas seem to fit what i observe over here, yes the original sirio 4000 do have the solid whip top they are useless in any wind so i replaced the vertical with an extended avanti original two extra sections and double skinned the bottom section with a second section from another avanti, now can you make any sense out of my other questions?? i am eager to hear your angle on it.

 

[RoadWarrior]

I also remember it being 27ft.
I'll never forget that as a friend and i put
it together inside my apartment...LOL...
My ex-wife came home early from work that
day and through a royal fit. To make matters worse,
we neglected to measure my doorway and the
darn hoop wouldn't fit out the door...LOL...
Not a good thing to happen when your wife is on a rampage.

 

[bob85]

hahaha i have been there i assembled my first avanti when i was 15 years old in our front room while my mom was at the shops, she caught me red handed and went crazy at my antics, it too would not fit through the staggered doorways to get it out and she very nearly helped take it appart the hard way

 

[freecell]

bob85,

i don't see how anyone could ever assemble, install, tune or use one of these antennas without seeing the relevance of the facts that i have presented here in this thread. it's encouraging to know that someone observes the similarities. as to the rest of your question, i have yet to experiment with any extended 7/8 wave designs. as such i won't be discounting anyones experience with them out of hand until i have worked with a few of them myself.

"now why would the designer tell chief that the 5/8 was the better antenna because of takeoff angle, if the gain is higher on the 3/4 then the radiation angle would i think have to be higher too for the 5/8 to beat it, then why do all my and my friends tests show the sigma4 style to be stronger locally and at distance than our regular 5/8 antennas?"

let's explore that statement for a moment. first you have to understand that one antenna can have more gain than another antenna although the gain in the first antenna might occur at a somewhat different to>angle than the second antenna and visa versa. it is also generally assumed by some that the lower to>angle is always the preferred angle of radiation for skywave ionospheric propagation. this can only be determined by the individual user within the parameters of the local surroundings and geography that he must deal with. to simply say that one antenna has a better to>angle than another antenna tells one absolutely nothing. what may well be an advantageous to>angle for one operator in one geographically unique location may not be of much use for another operator in a different operating environment.

i'll attempt to address some of your other questions here shortly.

 

[bob85]

i am all ears, i have experienced many times the situation where a halfwave gp or antron has had an advantade over a sigma into this side of europe which is to me short skip but i have never seen an antron get anywhere near to the sigma design for local none skip opperation, there seems to be too many variables when talking skip to just say one kind of vertical antenna is better than another for all possible conditions, past experience has shown this is not the case for me but more often than not the 5/8 and sigma style have the edge when working the longer distances into australia and the usa from my locallity, my i10k was working fantastic the other week when we had the crazy dx, i worked the whole of europe and the uk at least as well or better than the guys around me with their antennas mounted higher than mine, you could say i was whipping them in dx land, i told jay about it and he gave me a satisfactory explanation.

 

[RoadWarrior]

How high is your I-10K to feedpoint BOB85???
Mine right now is 18 1/2 ft. But, will be 47ft soon.
I do more local talking than Dxing. But, enjoy dxing.
As for you guys Sigma 4 discussion on angle of
radiation and such i will just sit back and read. As
i do not know the answers to make an input on the
subject.
It's been a long time since i used a Sigma 4 type antenna.
I do remember it got out very good.
But, those antennas are just to long for my use.
I'm just very happy and satisfied will the strength and
performance of my I-10k... Whether the Sigma 4 type beats it or not. LOL

 

[Master Chief]

I have a few minutes, I'll do my best.

at what point as we increase the angle between radiator and rods do the said rods become groundplanes?

DO you mean decrease? When they stop acting as part of the matching network. A "Ground Plane" antenna uses 2 or more elements to SIMULATE the earth's ground. The purpose of the gage in the Sigma IV is not to simulate the earth's ground.

now why would the designer tell chief that the 5/8 was the better antenna because of takeoff angle

You have this mised up a bit. Mr. Blaese's comment to me about the 5/8 is that for a single radiator, the highest amount of gain possible is .64 wave. Anything longer than that has undesireable wave patterns.[/quote]

if the gain is higher on the 3/4 then the radiation angle would i think have to be higher too for the 5/8 to beat it, then why do all my and my friends tests show the sigma4 style to be stronger locally and at distance than our regular 5/8 antennas?

I can't speak to that. I can speak to my own experience which is just the opposite. My 5/8 wave beat my Sigma IV. The Sigma IV is a end fed 1/2 wave radiator with a 1/4 wave matching section. Since it is not a ground plane antenna, I'm sure height above ground has something to do with it. Mine was 90' in the air. I didn't test it at different heights.

why does using 4 rods rather than 3 increase useable bandwidth on both the 3/4 and 7/8 length radiator?

It is written that 3 is better than 2 and 4 is better than 3, but any more than 4 is a waste. It would have to be engineered correctly, but it seems reasonable to say that 4 is more of a perfect cone than 3.

why does increasing the radiator length to 32 feet approx increase signal strength over all distances out to around 90 miles which is my max talking distance from my present location and at least 110 miles from my parents house?

Increase it over what? The regular sigma IV. We had concluded that the "7/8" wave antenna is actually an end fed 5/8 with a 1/4 wave matching section. 5/8 exhibits more gain than a 1/2 wave.

why does moving the gamma tapping point and retuning by altering gamma and radiator length for a low vswr while monitoring distant reliable stations ( houres of work ) allow an increase in signal strength on tx and rx by as much as almost 1.5 s units ( measured on yaesu ft990's ) over the factory tapping point and tuning instructions, the gains are permanent and more than the difference between our 5/8 and the 7/8 locally by almost 1s unit

You sure like to talk about all your hard work. The antenna manufactures need to build the antenna so any idiot can put it up and run it straight out of the box. Even Jay's antenna has measurements that work right out of the box. But, if you fine tune it, you can optimise it for where you are operating. Good job on your part! Most people won't take the time!

 

[Master Chief]

like we said before, if you want to prove it for yourself, remove them and see what happens. what you will see is the same thing that happens when you install any ground plane antenna without the radials or when you install a mobile antenna for base operation without the addition of an elevated radial system. the behavior is identical. VSWR measurements in the vicinity of 2.5:1 - 3:1 will be seen at the feedpoint.

just remember this:

MC stated:

"When the elements were brought UP, they now interact directly with the main element constituting part of the matching network;"

so you're saying that if the radials aren't swept up that there's no interaction and now they don't constitute part of the matching network? you yank the radials off of any ground plane based antenna system and let me know if you still have a "match." i believe a VSWR between 2.5:1 - 3:1 is typical for a ground plane design in the absence of its radial system. if you do then the radials aren't part of the matching network.

Remove them and you remove part of the matching network that makes the Sigma IV work. Its like removing the coil (et al) from the base of a 5/8 wave. Of course the match will be out of sight.

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."

MC posted:

"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.

the author even mentions the idea that the upswept radial elements could be replaced with a cone of the same geometry to achieve his design objective. i fully understand why he went with the skeleton element design instead.

I can explain it. Because they are not part of a ground plane system that is used to SIMULATE the earth's ground. A car's body does not sweep up. Anything above the antenna actually diminishes its performance, which is why it is recommended to mount it high in the middle. Truckers need to get the majority of the antenna, and at least the coil ABOVE the cab of the truck.

Where, anywhere do you see where the inventor said it is a "ground plane"? He does mention radials and they do project radially from the base, just as the main element does.

What the engineer DID was to design an antenna that met his design goals. He wanted an antenna that took up less room in the air. He took the ever popular J-pole and made it work.

Read this and tell me you don't see the simularities.
http://www.cebik.com/vhf/jp1.html

 

[Master Chief]

i have experienced many times the situation where a halfwave gp or antron has had an advantade over a sigma into this side of europe which is to me short skip but i have never seen an antron get anywhere near to the sigma design for local none skip opperation, there seems to be too many variables when talking skip to just say one kind of vertical antenna is better than another for all possible conditions, past experience has shown this is not the case for me but more often than not the 5/8 and sigma style have the edge when working the longer distances into australia and the usa from my locallity, my i10k was working fantastic the other week when we had the crazy dx, i worked the whole of europe and the uk at least as well or better than the guys around me with their antennas mounted higher than mine, you could say i was whipping them in dx land, i told jay about it and he gave me a satisfactory explanation.

When I first installed my I-10K, I had it on an A/B switch with the antron-99. The guy is skip land said the antron was louder (antenna b, as I didn't tell him what was what). But, the locals say a HUGE difference between the two.

We usually use the term, "take off angle" when talking about beams, but the term can be used here too. Depending the the height of the skip layer, different take off angles will reflect off the ionosphere and hit different parts of the skip zone. As an example;

A 1/2 wave antenna has a higher angle of radiation than a 5/8. With the skip layer at the same height, the signal from the 1/2 wave antenna will not skip as far as the signal from the 5/8. If the receiving station is in the zone favored by the angle of the 1/2 wave antenna, he will hear a stronger signal than from the 5/8 antenna. I can explain this more using a flashlight and a mirror if you like.

This is a whole different topic, but when using a horizontal beam antenna (not a ground plane) where the height above ground will change the take off angle, you can actually change your skip zone by varieing the height of the antenna! The ham radio contesters do this by having a motorized tower or a multiple stacks that allows them to switch antennas in and out of the stack.

So, the reason one antenna will work better than another antenna into a particular skip zone is base on its angle of radiation and the height of the skip layer.

Locally, the better of the two antennas will always out perform the other.

 

[Master Chief]

I'm just very happy and satisfied will the strength and performance of my I-10k... Whether the Sigma 4 type beats it or not. LOL

As far as getting the signal out in the air, the I-10K has LESS loss than the Sigma IV, so it stands to reason that it will put out a better signal. Locally, you would be hard pressed to beat it. When talking skip, mother nature gets in the way and its a crap shoot. Since they are not the same antenna, comparing them to eachother is difficult. But, if we took the Avanti Sigma 5/8 (my favorite) and the Penetrator (Jay's favorite) and compare those two 5/8 wave ground plane antennas against the I-10K, then the I-10K would beat them soundly every time.

Wait a minute, the I-10K WAS tested against those antennas and DID beat them soundly every single time.

And I'm not even talking about the mechanical superiority of the I-10K either; just the electrical characteristics!

 

[bob85]

chief i am warming to you, the i10k is the best 5/8 i ever owned so we have some common ground right there although i have not managed to get any significant gains over my initial settings following jays instructions, maybe i need to play with it some more, i think i understand the current theories on dx propagation i even learned about chordal hopping, i have been working worldwide dx since the late 70's and licenced since 96 but thanks for explaining the situation for those that dont know, and dont forget i am not the one that thinks i know how the sigma style antenna works i have all but given up on trying to understand whats really going on with it when a bunch of guys that all seem to be clued up are so far away from each other in how they think it works, i just know the 32 footers work great but are totally useless in mechanical strength, we have tornados and golfball hale forcast for later today and i want it to come, i will be one of the only people left on the air with my i10k and my locals will see that its money well spent if they buy a i10k instead of our usual weak ass antennas, have a nice day.