Avanti Sigma4: An alternative view point

[KomaToast]

There used to be a guy here in the DFW area that built these antennes for years and everybody thought they were great.

I lived about 40 miles from him as the crow flies and the best one I ever heard him talk on was what he called a 7/8 wave.
Don't know how long it was but I could hear him good and it was mounted on his test stand about 10 feet above the ground.

He moved out of state a few years ago and I haven't heard anything about him since.

KT

 

[BOOTY MONSTER]

i know there's some fans of the sigma 4/v4k here and thought ya'll might be interested in the replies i got on my thread about mine over at eham . on the 3rd page a guy pops up saying .....

"I was an engineer at Avanti when the Sigma IV design was being built. It's a J pole- nothing more and nothing less. No magic, "

and ....

"It's an end fed half wave- so same gain as a dipole IF you can keep radiation currents off the mast and the outside of the coax- this is the downfall of all of the groundplanes, J poles etc. "

http://www.eham.net/ehamforum/smf/index.php/topic,75921.0.html

so they have the same gain as a dipole . i wonder where his engineering degree came from ..... and if hes padding his resume .
seems the often quoted and seemingly revered W8JI is not a fan either . oh well .........

 

[HomerBB]

Experience is never the servant of debate.

"Among others, the Country Preacher said that, and he don't lie"

 

[bob85]

i can understand why mr cebik did not want to get into arguments with folk he said did not understand that design,

i agree with w8ji, our tests are far from scientific,

on the other hand the results are typical of what you will see if you install your antennas like 99% of people do, not isolated and not very high above ground,

unless that is you live in cali, then they only work better than a groundplane if you are ginger,

they work great if you live in TN and have the antenna isolated and choked like the one below

 

[bob85]

this is like magic roundabout,

in their own words from the avanti astrobeam article eddie showed me, the avanti engineers said they did not understand how the astroplane worked even though they made it,
if they don't understand the astroplane they don't understand the sigma4 either,

w8ji makes sense with his isolation ideas to me but i also have broadcast fellows telling me he's wrong to claim that a 4 radial groundplane needs to be isolated,
we have people claiming that a 1/2wave endfed does not need radials,

my own experience with the 1/2wave a99 following w8ji's ideas,
we found that isolating the mast, adding 1/4wave wire radials and choking the feedpoint cured terrible biting rfi/tvi in the shack AND improved signal strength,
removing the radials but leaving the mast and choke causes the rfi to return,

im open minded to the idea that the manufacturers don't know what they are talking about with regards to how to install their product,

none of the antenna manufacturers tell you to isolate the antenna, in fact when i brought up w8ji's isolation ideas jay and others claimed the 4 radials decouple the mast/feedline and needs no isolation,

we even have claims that the mast radiation is beneficial to the vector4000 ( i don't buy that ),

when the 5/8wave is isolated and choked and still loses to the vector is that just the 9+feet of height advantage of the current maxima ?

who do you ask when the smartest antenna guys you know of don't agree.

 

[BOOTY MONSTER]

i just go by my results . my first 5/8 did a lot better than the 1/4 wgp at the old place . the two 5/8wgp's i made here weren't impressive here 6-7 ft off the ground IMO , but the sigma/vector style did better on the ground and is doing much better in the air a little . W8JI suggested my 1/4 wave was constructed wrong ...... maybe so . that seems odd though ...... it was just a simple open circuit starduster type wire contraption . maybe i did build a really simple antenna so wrong , and much more complicated (IMO) antennas much closer to perfect . or maybe it's because i didn't compare at similar tip heights ..... just similar feed-points . but putting a 1/4wgp at the same tip height as the S/V just is not a option for me here and i doubt even a absolutely perfect 1/4 wgp at the same feed-point as the S/V type would perform nearly as well .

so for my situation a 1/4wgp is not the most effective omni and i'm not gonna take a step or two backwards in my performance results just because one of the (apparently/supposedly) brightest antenna minds on the forums doesn't like or care for my current omni .

W8JI had this to say about antennas bleeding and splattering when i commenter on how the imax is known to bleed ......

"So you are saying an antenna can cause "bleeding and splattering"? Exactly what is the non-linear mechanism in the antenna that does that? I wonder where statements like that come from, because unless the antenna has non-linear components in it...it cannot possibly cause intermodulation."

to which i had no reply .......... and i don't know what a "non-linear component" is . but i know imax and antron antennas are known to be bleeders and doing as you suggested bob (isolating and adding a proper choke and ground elements) helps or cures the problem .

or maybe the problem is im just a CB'er ? ...... maybe getting a piece of paper on the wall from uncle charlie will instantly make me smarter and make a 1/4wgp just as effective as my .875wl antenna within my installation limitations .

 

[bob85]

booty, its just a confusion of terminology, bleedstick is a cb term, when you take cb lingo to an amateur forum you can expect some will ride you like a mule,

i never experienced any none faulty antenna that causes you to crap on frequencies other than the one you are using,

now if one antenna puts out a stronger signal to your locals and causes more desensing of their receiver it could get incorrectly branded as a bleedstick,

say i put up a starduster on the same pole as my vector,
my locals would say my vector bleeds more than the starduster but thats nothing to do with the antenna been a dirty bleeder or none linear function of the antenna,
i have no cruddy connections acting like a dirty diode in my antennas,

my take on what a cb guy really means by bleedstick is an antenna that has common mode currents on the feedline that get into you or neighburs electrical equipment, bite your lip ect,

no radial endfeds have a reputation for that, w8ji's explanation is as good as any i have seen,
his methods of curing it have worked for us several times, not once have i seen any antenna maker or shop tell you to isolate your antenna, most think isolating antennas is cb hocuspocus,

when you follow the makers installation instructions to not isolate and to run skinny ground wires from the antenna to ground, and your 5/8wave gets a whooping from your vector who is to blame?

if your name is not kirchhoff its not you at fault.

use what works best for you on the mast you have

 

[bob85]

what did CEBIK mean when he said there was more going on in that design than was apparent to most people & that by folding the radials up towards the monopole a form of co-linear array could be created that could out perform a ground-plane,

i have already pointed anybody interested towards the arrl open sleeve article & skeleton sleeve fed monopole as examples of 3/4wave sleeve monopoles with in phase radiation from the lower 1/4wave,

lets look at what CEBIK tells us about j-poles,

http://www.cebik.com/content/a10/vhf/jp3.html

the claim from the j-pole camp is the sigma is a simple 1/2wave with no radiation from the lower 1/4wave,

here is the uniform omni pattern they imagine, its a close spaced wire j-pole with very little radiation from the lower1/4wave,

but what happens when its not a close spaced wire j,
you get radiation from the short leg,

and CEBIKS wide spaced model over ground

notice the lob sided pattern due to radiation from the short leg,
its clear that there can be radiation from a radial sleeve just as there is in the open sleeve antenna and skeleton sleeve fed monopole contrary to what the j-pole camp parrot on forums,

its clear that that radiation effects the pattern in the direction of the short leg and that maximum gain is in the direction of the short leg

radiating currents flow on the outside of the sleeve due to imballance, we have antenna mode and transmission-line mode currents flowing in the lower 1/4wave and the result is some radiation from the sleeve that is in phase with the upper 1/2wave just like the open sleeve /ssfm and sigma4,
the radiation can be seen in shockwaves cst plot of the vector 4000,
the whole antenna radiates in phase as AVANTI claimed,

the wide spaced j has one sleeve element, a direction of maximum gain, a direction of minimum gain, a front to back ratio and an average gain that falls between min & max gain,

the arrl open sleeve antenna has two sleeve elements giving a bidirectional pattern with max gain inline with the sleeve elements, are we starting to see a pattern/trend

the ssfm has 4 sleeve elements, it has an omnidirectional pattern with at least some of the benefits from the radiating sleeve,

http://k6mhe.com/files/ssfm.pdf

"but its a simple 1/2wave" is all they ever say/post,

not so, the in phase radiation is there for all to see in the cst plot shockwave obtained from sirio and posted for anybody interested,

make up your own mind, does the lower 1/4wave radiate in phase with the upper 1/2wave?
all we ever had from the j-pole bandcamp is "its a simple 1/2wave j-pole"
they have NEVER posted anything,



then we have a guy that doubts you can alter radiation angle,

i have posted what the arrl tells us happens with the open sleeve antenna when the monopole is extended,

lets look at what CEBIK says about the j-pole, is there a general trend when the monopole is altered in length?

altering the monopole length alters the phase relationship between sleeve and monopole, shortening the antenna has marginal effect on radiation angle so long as sleeve dimensions are adjusted for a good match,

lengthening the monopole longer than 3/4wave causes high angle radiation and less gain on the horizon just like the arrl claim for the open sleeve antenna,

the sigma/vector gamma allows many different length ratios to be tested with a good vswr without having to respace/alter the length of the sleeve to obtain a good vswr

we can only guess what the actual monopole electrical length is as the sleeve raises the resonant frequency,

it was my opinion based on experimental tests that the stock old style vector was too long and the original sigma4 too short, i posted that 8+ years ago when i was ukmudduck and this debate started on the cb forums,

why did i end up a little longer than shockwave?, maybe because i had my vector close to the ground & his was elevated high above ground,

why did the engineers at sirio shorten the vector monopole and lengthen the sleeve?
they claim it gives a lower radiation angle @ the same gain,

why do some people claim their 5/8wave outperforms their sigma4?
because they don't understand how the sigma works or how to set it up for best performance,

i am still waiting for anything from the j-pole camp parrots.

 

[jazzsinger]

No, I doubt they went to showing far field when the CST image is evidently intended to show what is as near field as possible, the RF radiation which is coming directly off the antenna skin.

I really don't know how I could be more clear about the issues presented in my previous post...?

Like you say this cst plot shows near field, its what happens in the far field of an antenna which really matters, and how the radiation from radiator and basket combine in the distance,and no plot is going to show that unless you got a 75 mile wide screen monitor, which given the present state of electronics is unlikely, so we can only assume the view Donald/Sirio has supplied does exactly that in the far field knowing it outperms all others without exception yet at those sort of distances.

@ Eddie, how do you know the guy in Europe who tested the antenna knows anything about antennas? has even got a clue how to solder properly?,isn't testing in a valley,which where i live has significant effect on any antennas radiation pattern, you will always perform better line of sight here up and down the valley than you will to either side where the hills exceede in many places 300m asl.

i have no idea who the guy in europe your reffering to is, but i have spoke extensively in the past with Donald by pm and through many threads on this forum and have ABSOLUTELY no doubts about his credentials or knowledge, what is this mystery Europeans credentials?

If Sirio listen to Donald which i know they do, then why does so many people on here doubt him? Sirio are no mugs and they certainly wouldn't listen to anyone who didn't bring something positive to the table, of that I have no doubt.

any mug can do a review, but actually understanding,describing,relating what they are seeing is wide open to misinterpretation and misunderstanding.

the first ever post Donald brought to this forum, Bob 85 and i spoke by pm or paltalk can't remember which, but Bob had previously shown me Donald's website and products, i told Bob right away and i'm certain he will confirm this, that guy who just posted is the guy who makes those antennas you showed me, Bob wasn't sure, i said pm him and find out, i was bang on. despite knowing nothing about Donald i knew who he was in one post, knowledge like his is rare and stands out a mile. I might not know as much as Donald, but I do know instinctively when someone is brighter than me.

I still find it hard to believe that you guys still debate with the only person ever to prove by cst that everyone else (except Bob and a handful of others) who said it was a j pole with non radiating basket were WRONG. He's proved the basket does indeed radiate in phase with the main radiator, where everyone else said it didn't radiate at all with a handfull of exceptions. the great Masterchief the biggest promoter of this wrong assumption, no longer shows here, WHY IS THAT?

what happens in the far field we can only assume, but countless tests in many areas and from many people always come to the same conclusion, in the far field the sirio vector 4000/avanti sigma 4 it was improved upon from, both have something happens in the far field that make them see a much further transmitted signal than conventional 1/4,1/2 or 5/8 waves, i wont even mention .64 waves as to me that is nothing but snake oil and even if it was true would be nigh on immeasurable, what happens on these antennas is measurable by the simple fact that switching from any verticle to sigma 4/vector 4000 gives you more chance of being heard with a better signal at extreme range, of that in my mind, there is no doubt.

i'm not saying they are the best skywave antenna ever, as that is nigh on impossible to prove as its mainly down to conditions and i've seen 1/4 wave gp's,1/2 and 5/8 waves outperform beams mounted on same mast many times, but when it comes to extreme line of sight antennas, i've only ever seen one, and so has Bob that gave the sigma 4 a run for its money, that was a ham international big mac and theres not many of them left to do direct comparisons tests due to their pish poor construction and many weak points, not to mention severe weather that batters northern europe frequently where most were sold.

 

[jazzsinger]

Well guys here is Ole Grampa doing his thing with modeling again. I used my Sigma 4 model to compare it to the same model with the radiator extended out to 36' feet. I then generated a pattern and captured a trace of the pattern to overlay with the default model Sigma 4 model that I published earlier here on the forum.

Hopefully you will see that what happens is exactly what Shockwave tells us happens when you extend the Vector radiator out longer to a full wavelength.

YouTube - ‪Booty Monster's question re: a full wavelength Vector 4000‬‏

did you try extending it to around 1 and 1/4 (circa 45 feet) wavelengths Eddie, cause if i'm reading Donald and arrl statements correctly thats what would be required as the bottom 1/4 wave of radiator is shielded therefore isn't a part of the radiator as such. that would leave you a 4:1 ratio radiator above the baskets cancelling effect. just a thought for you.

 

[jazzsinger]

booty, its just a confusion of terminology, bleedstick is a cb term, when you take cb lingo to an amateur forum you can expect some will ride you like a mule,

i never experienced any none faulty antenna that causes you to crap on frequencies other than the one you are using,

now if one antenna puts out a stronger signal to your locals and causes more desensing of their receiver it could get incorrectly branded as a bleedstick,

say i put up a starduster on the same pole as my vector,
my locals would say my vector bleeds more than the starduster but thats nothing to do with the antenna been a dirty bleeder or none linear function of the antenna,
i have no cruddy connections acting like a dirty diode in my antennas,

my take on what a cb guy really means by bleedstick is an antenna that has common mode currents on the feedline that get into you or neighburs electrical equipment, bite your lip ect,

no radial endfeds have a reputation for that, w8ji's explanation is as good as any i have seen,
his methods of curing it have worked for us several times, not once have i seen any antenna maker or shop tell you to isolate your antenna, most think isolating antennas is cb hocuspocus,

when you follow the makers installation instructions to not isolate and to run skinny ground wires from the antenna to ground, and your 5/8wave gets a whooping from your vector who is to blame?

if your name is not kirchhoff its not you at fault.

use what works best for you on the mast you have

i agree with Bob Booty, going on a ham forum with cb lingo will get you mocked, splattering, is caused by non linear amplification, not the antenna, bleedover is usually caused by overloading the front end of a receiver/an amp splattering, the term means to bleedover into adjacent channels or even other parts of the spectrum, depending on severity and frequency of the harmonics produced, they may or may not be strong enough to be noticed or cause rfi to other service users, don't mean they ain't there though.

like Bob i would instantly recognise your bleedstick term as an antenna known to produce olympic status rfi/tvi or excessive noise pickup due to common mode current flowing on shield outer/causing it to form part of the antenna as well as part of the supposedly shielded transmission line.

many hams are quick to mock cb'ers and their terminology, ironically even ones less smart than the person they are mocking, as a certain ham found out with me when he tried to mock me on an amateur forum, and was brought crashing to earth by another ham who isn't as narrowminded to cb'ers and posted an argument between me and said ham from another forum i had long forgot about where i made him look like a tit, just before i got banned, duhhh, which incidently is what my signature is about as it was a quote from Bob to that very same ham who was celebrating the fact i was banned therefore no longer able to dispel his bullshit, sadly for him Bob wasn't banned and neither were a handful of other hams on that forum that have shown me nothing but complete respect, even in their section of said forum.

ironically after I was banned, yet another ham (i beleieve) posted about said ham and me that he missed me as the internet was made for "Jazzsinger v Retard" threads, so not all hams are the same just as not all cb'ers are the same, despite my many disagreements with Garth over the years, never once have i seen him and many other hams i've argued with post bullshit in the cb section of this forum, these guys have my respect far more than any cb'er or ham for that matter passing on myths through ignorance. they tell it like it is,its that simple. I respect that even if it'S ME THEIR PROVING WRONG.

better too keep your mouth shut and learn,than to open it and prove your an idiot in presence of those who obviously know more, that applies to any forum on any subject.take me on any forum about any subject, even ones i don't know, i'll have the bullshitters all tagged in hours, they all have one thing in common, constantly linking to others for information and shallowness of knowledge in their answers, especially when challenged, if they really knew they'd type it themselves in depth. i generally find people who know, are passionate about a subject, therefore tend to over elaborate.

 

[AudioShockwav]

I even did it for you.

http://www.worldwidedx.com/cb-antennas/161948-new-thread-debate-v-4000-a.html

Have fun.


73
Jeff

 

[kb9ezl]

Saliut 27 Antenna

I've tried all kinds of CB and Ham antennas and as far as DX on 10 meters this design
I found was the best. The only problem with the antenna was the ability to hold up
against ice storms. Not many can unless they are made of aircraft aluminum grade.
This antenna doesn't need to be mounted high to work overseas DX. If you want local
coverage it needs to be mounted high. Mechanical design is the only problem with it
since it has a tall vertical element. The Saliut 27 wasn't made with high quality
aluminum so an ice storm will bring it down. http://www.worldwidedx.com/images/smilies/sad-smiley-019.gif

Dennis

Interesting Read Bob, Thanks for sharing



My .2....

I Lived in a very rural area, had a nice tall 3 story House, easy roof to work on, and an about perfect test base. On the roof I had a pair of 10 foot Tripods separated by 45 feet of roof, 20 Feet of Well pipe leaving the base of the antenna at 63 Feet. At the time was no such thing as Antrons, Sirio, larrys, Macos, Etc...

I did have the Sigma IV, Starduster, Penetrator 500, and a Sigma II. Surrounding Terrain was Flat except a large Hill (Ski Hill) to my SW at about 8 miles. While I wasn't perfect in my test I was pretty thorough.

Radios used were:
Base: Johnson 500/Collins R390, Tram D201 D&A Phantom.
Mobile: Hygain V, 102 Whip (roof mounted Aprox. center of car roof), and an Old School Palomar 4 transistor mobile.


The tests were run over about a week. Consisted of talking to the mobile without interruption to a local (1940 foot elevation)Mountain, about 60 miles as the crow flies. For base to base comparison I used 3 contacts. One at about 20 miles Moonraker 4, and a Penetrator. One at about 55 miles, Starduster. And one about 110 miles with a PDL II.


Back in the day gas was cheap, time was plentiful, and I was a pretty full of energy.


Up until about 15 years ago I still had the Paper with all the appropriate signal strengths, and distances. Unfortunately not anymore.

I do recall the antennas were all within a small range on my R390, The Tram was a bit more difficult to read but results were the same.

stationary mobile to base, and base to base the Sigma IV was the winner. though for the first 20 miles the difference was minimal. Signal was measured about every 5 miles at a quick stop. it wasn't until 50+ miles the antenna began to really shine.

I was able to talk to the mobile the full 60 miles QRP except in the case of the Starduster, was a few times I lost signal. This was rolling and could be attributed to conditions.

Base to Base was pretty much a repeat. The Sigma IV beat all the others with a noticeable signal increase both TX and RX. at 110 miles the Sigma IV made enough difference to allow a reliable conversation with less then 25 watts possible.


Also years later I did some tests, which consisted of a Penetrator and a Starduster copy, VS a Larry... Same results.

Interestingly I also had a very cool fairly close copy (Spec wise) of the Moonraker 4... I don't remember the maker (Cushcraft maybe?) but it was pre-assembled, you just bolted the boom together, telescoped the elements, locked the hinged elements in place and you were done... Very impressive antenna, or so I thought.

Carefully measured and tuned the antenna. Put it on my 10 foot tripod in place of the Larry.... Boy what a huge disappointment, the larry did better both TX, and RX.

Now in this case, it shouldn't have been, but it was... antenna was mounted about 36 feet center boom. The Larry was obviously a bit higher due to its profile.

Only thing I can figure is possibly because I was in a slight hole. Lived right on a lake, and even to the South where it was level the Larry still kicked its butt.


Moving forward to the mid nineties I compared the Sirio Sigma IV with the Antron.. What a huge difference. No matter the distance. I will say the V58 was also a big difference, was not as strong as the Sirio though.


Over the years I've owned the original Avanti, the Larry LW150(think that was it) A gold anodized copy CTE?, and the Sirio. All were decent antennas, the gold version was very annoying to get tuned up, but once I managed it was great. None of them matched the build quality of the Original. I will add Attention to detail in assembly was important on all of them.

Since my Start in radio in the 70's I've owned Just about every antenna made My all time favorite is hands down the Sigma IV. Copies 2nd, then Sigma II, and Penetrator. Would like to try the some of the modern antennas but I just cannot Justify the cost.

 

[M0GVZ]

A Moxon works great on 10/11m, has more gain than the vertical mono element antennas and will work well from 20ft. You get the additional bonus of being able to null out QRM so if you're in the north east of the USA and want to work Europe you don't have to try and listen through 30+ of CONUS.

If I could only have one antenna for 10/11m that would be it. Simple to build, cheap and not a ridiculous size either.

 

[Marconi]

kb9ezl, I have an original Sigma 4, made by Antenna Specialists. I've reported that the S4 is a great antenna, but my signal reports never did show it to be much if any better that several other designs from a Starduster to the I-10K...among others that I own.

In reading the account of your results I find it curious that your S4 seems to be just as effective as what Bob85 reported for years with his Vector 4000 Hybrid...being easily detectable as superior to all others.

At some point on two occasions separated by a year or two back around 2006, I did some testing with my S4, while talking with Bob almost daily via email and comparing results to several other popular CB vertical antennas I owned. I did all kinds of things to my S4, and often as I was trying to get better results at Bob recommendations. I was never successful at seeing much if any improvement, and that disappointed both of us.

At some point near the end of these projects Bob told me that the S4 was not capable of getting the long range results his modified Vector showed him. I think now that Bob said that as a conclusion, but at first it really pissed me off that after all our words and lots of work over several years, back and forth up and down, he would tell me at the very end, after all was said and done, such was the case...not only with my S4, but also with one that he previously owned.

All of these accounts noted here present a rather obvious question as to what was reported over all time for this particular antenna. IMO, there is no way to really test, for sure, in the manner we CB hobbyists have at hand...to do real testing and thus we see differing reports at different locations. Your report is just another of such differing reports.

I thank you however for posting your results, and I don't question what you report, I also find my S4 to be a fine antenna.