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Post by bob85 on Mar 3, 2009 11:51:21 GMT -5
never seen the real lw150 to comment, of the folk that claim to have owned both some say the lw was better built and other say the avanti was best, for me the best performers are the 4 radial extended radiator version, its just a pity they are nowhere even close to the strength of my i10k, looks like we are never going to see eye to eye on this one, "there is no antenna with as low or lower a take-off angle of radiation than a .64, period, end of story" wrong, there is more than one antenna that has a lower angle of radiation, to get the best out of any phased array first you must understand that it is a phased array, if you deny that you are on a none starter, just tuning like other antennas aint gonna do it, i have given the information elsewhere about how they work, i can live with some people believeing it works like a j-pole, i wont lose any sleep, i will go with my own and friends tests plus what antenna smart folk such as cebik and others have said, you stick with what you saw in your tests and we are all happy
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Post by ic751a on Mar 3, 2009 19:34:29 GMT -5
never seen the real lw150 to comment, of the folk that claim to have owned both some say the lw was better built and other say the avanti was best, for me the best performers are the 4 radial extended radiator version, its just a pity they are nowhere even close to the strength of my i10k, looks like we are never going to see eye to eye on this one, "there is no antenna with as low or lower a take-off angle of radiation than a .64, period, end of story" wrong, there is more than one antenna that has a lower angle of radiation, to get the best out of any phased array first you must understand that it is a phased array, if you deny that you are on a none starter, just tuning like other antennas aint gonna do it, i have given the information elsewhere about how they work, i can live with some people believeing it works like a j-pole, i wont lose any sleep, i will go with my own and friends tests plus what antenna smart folk such as cebik and others have said, you stick with what you saw in your tests and we are all happy I was referring to a single antenna, and obviously an omni since this is the context here, but it sounds like you're referring to a multiple antenna array. Also, I was kind of hoping to bring Eddie (Wolf) out of the ether as I know he has a phased omni he believes is higher gain / lower angle.
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Post by bob85 on Mar 4, 2009 4:36:20 GMT -5
i am refering to the sigma style antennas, they are a form of phased array and need setting up correctly to work at their best, have a look at my post www.cbjunk.com/forum/viewtopic.php?f=23&t=526 i spoke to eddy ( wolf ) about the sigma style antennas, eddy claims it is a form of phased antenna, im sure he made a post on wwrf in an old sigma thread about making the angle of radiation switcheable, i would like to see an original larry but nobody seems to have any pics, check this tagra bt104 out, does it look like a larry? i had the none anodised version, thecbmuseum.blogspot.com/2008/06/tagra-bt-104-sigma-iv.htmlfound the instructions for my old commtel 444 in my moms loft yesterday while removing insulation ready for new thicker stuff.
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Post by ic751a on Mar 5, 2009 18:50:04 GMT -5
Hi Bob,
Excellent article and I did read the patent from beginning to end. Interesting proposition that some sort of phasing of a 1/4 wave plus a 3/4 wave, or a pair of 1/4 waves and a 1/2 wave, or a pair of 1/2 waves with one halfway inverted would outperform the low angle of the .64, ...?
I wish it were all true. Not saying anyone is lying, I've just been there and done that with the LW-150 and hated, I repeat, HATED to let it go, but I did.
I do, however, still have my 1975 Penetrator. I kept it instead because at 45-70+ miles it performed better on both RX & TX in comparison to the LW-150.
I assembled the LW-150 as per instructions, tuned the Gamma as per instructions, and as always used 8 turns on an 8" former common mode current choke in the coax just under the antenna - since my uncle who got me into CB in 1967 was a Ham and showed me that trick to keep away from common-mode radiation, TVI, etc...
What can I say?
... I tried it.
... I WANTED it to be better!
... I had already used the Penetrator for at least 6-7 years and HOPED I had finally found a better antenna than the Penetrator that would upgrade my station performance, and look oh-so-cool while doing it.
... I loved the build quality of the LW-150 and was proud to be the first in my area to have one.
... I thought it was beautiful and if anything, I was biased in IT'S direction.
... I conducted tests for a month and finally, tired from all the hopeful but fruitless attempts to find that magic formula that would cause the Penetrator to take a backseat to the LW-150...
... I had to concede that the LW-150 was just not going to beat or even approximate the performance of the Penetrator and reluctantly,
... I sold it.
Now I wish I still had it just for testing and posterity sake, and to show off the build quality. I'd probably have it up just for a 2nd monitor rig, but it's gone and I've never really missed it.
I would compare it's performance to a Maco that was installed maybe 10'-20' higher than the Penetrator. It was good but just didn't hang in there for the distances that the Penetrator did.
I also recall a few others in town who later installed one of the copies and just couldn't keep up with my Penetrator station.
I read their claim of 1-1.7dB more than a .64, and I fully believe that is possibly correct, I just doubt the angle of gain. Near-field tests may have shown gain, but my far-field tests showed loss.
Thank you again for such a well-written and researched article, you actually had me considering trying one again, ...until all the memories came back at how disappointed I remember being. It was a beauty and I sure wanted that to be THE antenna of choice.
If you have one, use it and enjoy it, but I still believe a .64 will get your signal farther, ground wave.
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Post by ic751a on Mar 5, 2009 21:08:53 GMT -5
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Post by bob85 on Mar 7, 2009 14:13:06 GMT -5
751 glad you liked the post, what you describe in your results is exactly the opposite to what we see in our tests over similar distances, all i can tell you is it takes a lot of experimenting to get the sigma style working at its best, the 4 radial extended version works better for us than the original avanti.
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Sandbagger
Administrator/The Boss
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Post by Sandbagger on Mar 7, 2009 22:26:08 GMT -5
751 glad you liked the post, what you describe in your results is exactly the opposite to what we see in our tests over similar distances, all i can tell you is it takes a lot of experimenting to get the sigma style working at its best, the 4 radial extended version works better for us than the original avanti. My Sigma 4 was the best performing omni I ever owned. I picked up 1 "S" unit in signal over my old 5/8th wave. Although to be fair, I lived in a relative hole, and my range didn't extend much further than about 30 miles, and the people who noticed my increase in signal all lived within 5 miles of me. I now live at a much higher elevation, but I can't do the same A-B comparison to see how it works at different distances.
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Post by mark4 on Mar 14, 2009 20:37:48 GMT -5
Best antenna I ever owned is the one I'm using now. Radio Shack's .64 wave found it last summer NOS.
I also have a Penetrator put away but it needs to be overhauled.
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Post by zman on Mar 30, 2009 11:51:38 GMT -5
Someday i will get my Sigma 4 out of the garage and put it back up. I had it on a 30' push up pole but took it down because I didnt like the way it waved around in the winds. IMHO the Sigma 4 is one of the best antennas made aside from the Avanti sigma 5/8 which i have up on the roof now.
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Post by skipshooter on May 18, 2009 11:32:22 GMT -5
i have 2 lw 150 antennas one is new 1 is going up to replace my army stick the stick works well but the ears are not the best i am down in the valley so maybe this will help my ears i will reply with what i find out after installing
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Post by 68rd400 on Sept 2, 2009 8:08:38 GMT -5
found the instructions for my old commtel 444 in my moms loft yesterday while removing insulation ready for new thicker stuff. hi bob, I just found my old comtel 444 antenna, well most of it. theres a few bits missing I think. a couple of the radials are broken too. I was wondering if you could possibly scan the manual you have for me? or possibly tell me if there are measurements for the antenna on it? thanks in advance.. 68RD400 N. Ireland
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Post by zman on Sept 2, 2009 21:28:01 GMT -5
Well i put up my Sigma 4 the other day and tried it out on CH 38 LSB. It seems to work well enough but i think my Sigma 5/8 definetly has an edge on it when i talk local. I used the sigma 4 to check into a 10 meter net Saturday night (using the internal tuner in my Icom 746) and i managed to talk to a few locals. I think i will put the Sigma 5/8 back up.
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Post by zman on Sept 20, 2009 19:27:00 GMT -5
There is an original Avanti Sigma 4 for sale on Ebay right now.
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Post by mark on Oct 23, 2009 8:07:19 GMT -5
I agree on the sigma 4 working great for somebody living in a low lying area as I put one up with fantastic results when I used to live in the Salt Lake Valley. I too think I remember seeing the antenna model of a j pole and it has a higher radiation angle than a 5/8 GP. However!?!?! If you live in a flat area and want to do the best ground wave signal possible, there is only one way to do it. Get a good quality 5/8 Ground Plane (no Imax or Antron will ever do here) and put it up as high as possible! A good 5/8 wave GP (like a super penetrator) placed on a tower at 70 or more feet, can do AMAZING THINGS!!
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Post by cbrown on Oct 23, 2009 12:35:49 GMT -5
I had the Avanti Sigma II (AV-170) back up in the late 1970's. Performed very well.
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Post by bob85 on Oct 25, 2009 5:53:40 GMT -5
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Post by bob85 on Oct 25, 2009 7:04:23 GMT -5
there is no hype involved in the sigma4 design, the hype/confusion comes from the people who claim it is a j-pole, the j-pole crew have no technical answer as to how it works, their claimed inferior performance to a 5/8wave can easilly be proven to be false in field tests over real earth, the j-pole crew have not retracted/edited their claims which confuses newcommers to the topic, there is no confusion about its performance, all the clues are there in the patent including the variations on the design and a means to increase gain even further over the 5/8wave groundplane, when tuned correctly for maximum signal at distance the design outperforms any 5/8wave as claimed in the avanti patent, it has both higher gain and a lower radiation angle, the design also suffers less with coupling to its surroundings than conventional groundplanes, all i ask is that you do your own tests, buy a sigma4 or the better performing but weak constructed vector 4000/lw150, tune it for maximum signal at distance and report your results truthefully, more info in these links, www.cbjunk.com/forum/viewtopic.php?f=23&t=526www.worldwidedx.com/cb-antennas/31799-avanti-sigma4-alternative-view-point.htmlwww.worldwidedx.com/cb-antennas/36412-modified-vector-4000-a.htmlwww.worldwidedx.com/groups/antenna-group-d2-antenna-group-page3.html
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Post by ic751a on Nov 7, 2009 11:53:31 GMT -5
I looked at the pdf file of the pattern of that Skelton cone, and it looks just like a J-pole without the irregular pattern.
Now, I may have to try the 7/8 design, but I've already tried the 3/4 and wasn't impressed.
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Post by bob85 on Nov 8, 2009 17:55:08 GMT -5
yes it does look like a more symetrical jpole pattern, that is a direct fed 3/4wave using 1/4wave parallel sleeve elements, the radiation angle of sleeve antennas is steerable through changes in relative element lengths and angles, with propper tuning the 3/4wave avanti outperforms a 5/8wave, if it does not then its not tuned for best signal performance at distance, the extended version works even better but like the 3/4wave if its not tuned correctly it wont work at its best,
good luck with the 7/8wave.
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Post by ic751a on Nov 8, 2009 21:26:18 GMT -5
I keep reading the term, "Tuned correctly" as if there is some sort of magic wand formula... I would expect that there is a set length for a certain frequency of choice, and a certain gamma adjustment which will be the only length providing a 1:1 resonance for that specific frequency of choice. Is there more to it than that, and if so, please explain!?! I set my LW-150 BY THE BOOK and tuned it to as near a 1:1 swr as possible. So are you saying I did something wrong? Was I supposed to align it with the circumference in meters of the rings of Saturn divided by Pi times the resonance of a banana or something super secretively mysterious which only the extremely privileged hierarchical members of the Cult of Ultra-resonant Resonating RF Resonance know, but can never share? I'm getting a bit tired and frustrated (can you tell?) of hearing about this ultra-incredible antenna which I tried and proved to myself (and about 25 others in this area who were watching) was not as good as a .64 Hy-gain Penetrator, what more should / could I have done?
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Post by bootymonster on Nov 9, 2009 4:59:26 GMT -5
heres a post by jack/freecell from his forum at 292 Radio Shop / FireCommunications Network.......The Export Radio Specialists! . its pretty cool . he worded it so even someone with limited antenna knowledge (like me) can understand it . i find its also easy to visualize the 1/4 wave ground plane growing into a sigma 4 .
i asked if i could post it around and he said yes as long as i give him credit for his info , which i would have done anyway . thanks again jack
.................................................. .......
"i have posted this some time ago in The Members Portal, i've decided to release it here first in the Antenna Group. let me know what you think........
Where the story begins........
when the ground wave field strength of vertical antennas is examined, it is found that if a 1/4 wave antenna has 100 mV. field strength at 1 mile, a 1/2 wave vertical will have about 125 mV., a 5/8 wave will have about 140 mV., but a 3/4 wave will have only about 80 mV..
the conditions under which these tests were conducted assume a fixed amount of transmitter power with all antennas tested matched to the feedline so that Z=50 or R=50, X=0 at the target test frequency and that all antennas are tested at the same exact feedpoint height.
as the antenna design with regard to wavelength^ is extended from 5/8 wave to 3/4 something not unexpected occurs. additional lobes appear in the upper elevation plane reducing the amount of field strength in the major lobe at the lower takeoff angle and the measured ground wave signal strength is reduced.
(^ electrical, not physical)
and so, conventional antenna theory is confirmed and vindicated not only by the test results above but given further credibility and affirmation by the many college level engineering texts that have been written on the subject.
whether or not this was the starting place for the engineers at Avanti when they contemplated the design of the controversial Avanti Sigma IV is not known but it makes sense that this would be as good a point as any. herein was the challenge presented to not only defy conventional theory and design but also in the process to come up with a design that eliminated the formation of these additional and wasteful high angle lobes while increasing the ground wave gain and at the same time reducing the sensitivity of the design to objects in the near field which tend to wreak havoc with feedpoint matching and distort the radiation pattern.
first let's re-establish a few facts so that it's easier to follow along with what lies ahead.
beginning with a basic 1/4 wave ground plane with radials at a 90 degree right angle to the active radiating element, typical input impedance is roughly 36 ohms at a predetermined height above earth ground. as the radial elements are lowered towards earth ground the input impedance rises. conversely, as the radial elements are raised the input impedance is lowered.
as the radials are raised towards the radiating element something else interesting occurs. the radiating element becomes less sensitive to the influence of surrounding objects and terrain in the near field, allowing the antenna to be mounted in locations and at heights above ground that would be extremely deleterious not only to the feedpoint match but also to the radiated pattern emanating from the radiating element.
as the radials are swept upwards towards the radiating element capacitance between the radials and the radiating element increases, effectively raising the resonant frequency of the system or causing the electrical length of both the radials and the radiating element to be shortened.
so, the closer the radials come to the radiating element the more the coupling capacitance increases, the higher the resonant frequency climbs and the lower the feedpoint impedance drops, approaching single digits and 0 ohms.
also remember that the gamma match is used to match 50 ohm feedline to loads representing less than 50 ohms. let's assume at this point that we have raised the radials to the point that the angle represented at the apex (bottom of the antenna) is such that it approximates a value of 15 degrees. at this point we have gross mismatch, (single digit impedance) a 3/4 wave vertical element that started out resonant in the middle of the cb band (or whatever) and is now resonant much further up the band (1/4 radials included) but we have eliminated the sensitivity of the vertical element to surrounding objects and terrain which provides a distinct operational advantage, mentioned previously. now we have to match the feedpoint to the feedline and provide some compensating influence to counter the rise in the resonant frequency of the radiating element.
as we can see from the above the gamma match is the logical choice for impedance matching and we can re-resonate both the vertical element and the radials by increasing the physical lengths until resonance is re-established at the intended operating frequency. we can lengthen the radials and simultaneously improve the frequency vs. bandwidth attributes AND provide additional physical support for the radials by simply connecting an aluminum loop that will intersect the radial ends while extending the physical lengths of each from 89.5" to 107".
with that done we can now direct out attention to re-resonating the vertical element for the intended operating frequency by providing additional tubing length (inductance) beyond what is dictated by the standard 3/4 wavelength formula. with that accomplished all that is left is to implement the gamma match and then adjust these last two variables to match the feedline while maintaining resonance at the target frequency. this can be the tricky part as the gamma strap, referred to by SigmaIV enthusiasts as the "Dogbone" also comes into play with these other two adjustments.
after all of the hard work what you end up with is a full-size modified 3/4 wave vertical that easily produces twice as much signal as a conventional 3/4 wave @ 80 mV..
as to all of the questions posed by the pundits from the J-Pole camp i have only this to say. you have no clue what you're talking about. even the most uneducated person can look at these two designs based on nothing but geometry and determine that they can't be the same antenna design based on the dissimiliar symmetry alone. what seemingly escapes most of you is the way that the feedline smoothly transitions into the SigmaIV while closely maintaining the same basic concentricity (inner conductor to outer conductor diameters) as that of the feedline with no exceptions as to the size and type of feedline used. this efficiency factor coupled with the full-size 3/4 wave radiator and revolutionary upswept radial design is why the SigmaIV was ahead of its time when it was first introduced to the market and lends itself to the design of even longer antennas (in terms of wavelengths) to produce even higher gain figures without the restrictions presented by the development of multiple lobes as was the case in the conventional designs that we were previously limited to."
........................................
now , any thought on if this antenna performs better directly connected to metal mast and earth ground vs. insulating/isolating if from conductive mast and earth ground ?
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Post by mark on Nov 9, 2009 10:03:32 GMT -5
Well, good God. I talked to one of the guys that was on the design team at Avanti back in the day. I spoke with him about two years ago at length about this very antenna and the shocker of all shockers was that he told me that this antenna was designed by a guy at Avanti who had no formal technical training at all and was 100% self taught (nothing wrong with that but just giving the background). Your quoted article while interesting has several fatal flaws in it. Most glaring is the fact that the inverted cone is NOT an "upswept radial system", it is ONLY there for impedance matching and NOTHING else! Also that the 3/4 wave antenna gives less field strength than a 5/8 wave GP and this is a good thing? This antenna is one half wave above that cone! I was told this IS IN FACT DESIGNED AS A HALF WAVE J POLE and was done that way NOT to make it outperform a 5/8 but to create a product for people who did not want to have the large horizontal radial system. He admitted and said in no uncertain terms that their own 5/8 wave GP outperformed it in their own field tests. I relay this story for two reasons, One is that I LOVE that antenna and used one for years and always wanted to know about how it worked, and number two is that I get upset when technical errors get propagated among people who are trying to learn and they are taken as gospel truths. There are a couple other details which are flawed in this guys logic, but the worst thing he ever said was that, "even the most uneducated person can understand this". That is an extremely inappropriate statement, given that if you disagree, then you must be unbelievably dumb... I have been into this hobby for over 30 years and I know just enough to be dangerous, but I am posting this because the write up is in error and very misleading. The only thing worse than no information is disinformation and it is my one big pet peeve with the radio hobby... Ham radio is without a doubt the worst offender when it comes to dis/mis information. CBer's are usually not so bold about what they "think" they know.
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Sandbagger
Administrator/The Boss
Posts: 6,245
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Post by Sandbagger on Nov 9, 2009 13:11:41 GMT -5
Well, good God. I talked to one of the guys that was on the design team at Avanti back in the day. I spoke with him about two years ago at length about this very antenna and the shocker of all shockers was that he told me that this antenna was designed by a guy at Avanti who had no formal technical training at all and was 100% self taught (nothing wrong with that but just giving the background). Your quoted article while interesting has several fatal flaws in it. Most glaring is the fact that the inverted cone is NOT an "upswept radial system", it is ONLY there for impedance matching and NOTHING else! Also that the 3/4 wave antenna gives less field strength than a 5/8 wave GP and this is a good thing? This antenna is one half wave above that cone! I was told this IS IN FACT DESIGNED AS A HALF WAVE J POLE and was done that way NOT to make it outperform a 5/8 but to create a product for people who did not want to have the large horizontal radial system. He admitted and said in no uncertain terms that their own 5/8 wave GP outperformed it in their own field tests. I relay this story for two reasons, One is that I LOVE that antenna and used one for years and always wanted to know about how it worked, and number two is that I get upset when technical errors get propagated among people who are trying to learn and they are taken as gospel truths. There are a couple other details which are flawed in this guys logic, but the worst thing he ever said was that, "even the most uneducated person can understand this". That is an extremely inappropriate statement, given that if you disagree, then you must be unbelievably dumb... I have been into this hobby for over 30 years and I know just enough to be dangerous, but I am posting this because the write up is in error and very misleading. The only thing worse than no information is disinformation and it is my one big pet peeve with the radio hobby... Ham radio is without a doubt the worst offender when it comes to dis/mis information. CBer's are usually not so bold about what they "think" they know. Well the last thing we should be doing here is getting into a pissing contest with each other over "what might be", and "what it looks like" etc. and just look at it objectively. I'm curious about one thing you said, in reference to the guy at Avanti admitting that the 5/8 wave antenna "outperformed" the S-IV. If that is the case, and they knew it, then why did they rate the S4 with a higher gain value? Also I find the part about the designer having no formal education to be interesting. It brings me back a number of years, to when educated people were always telling me that the things I was building would never work. Heck I didn't have enough formal education then to know any better. But my lack of education allowed me to build them, and the funny thing is that often the things I made DID work. And only after analyzing them and figuring out why they worked was it understood. So many times knowing too much makes people say no to things before they ever try them to see if, in fact, that they might just work pretty well after all. I know I've said it before when the subject of this antenna comes up, but I owned one and for me, it was the best performing omni I ever owned. Back in the 70's and early 80's, the locals were all very competitive when it came to signal strength, and I would've had a fit if my signal dropped even 1/2 of a "S" unit to one of the locals, and there was no corresponding reason why (Like bad weather etc.). I knew what my signal was to each and every person I talked to regularly, and when I went from a 5/8th wave (which had replaced an Astro plane and a 1/2 wave before it) to the S4, everyone saw a slight increase. I'm not going to claim 3 or 4 "S" units or anything so ridiculous, but depending on the person and how sensitive their "S" meters were, I jumped anywhere from 1/2 to 1 "S" unit. A guy 7 or 8 houses down the street from me had the Sigma 5/8th, and my signal was stronger than his was. Now I've heard all the technical banter on how a 3/4 wave antenna radiates with such a high angle of radiation, that it wouldn't put a usable signal out to the horizon. I've read the claims that the S4 is basically a "J-Pole", and/or that it's only a 1/2 wave etc. So if any (or all) of this is true, then what accounts for my superior performance observations? Maybe it is in the angle of radiation, and the fact that I was in a relative valley compared to many of the others in the area may have played a part in this antenna being ideal for me (An Astro Beam on top of a 40' tower finally bested it). But one thing's for sure, it's no A99........... And don't blame the hams. CB'ers also stick to some strange theories. Where else can a 2 "pill" amp put out 400 watts?
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Post by bob85 on Nov 9, 2009 14:34:38 GMT -5
751 there is no majic tuning super resonance , i have stated many times that doing it by the book is not the way to get the best out of the design, you already said how long your lw150 was and thats too short even for a 3/4wave as was noted in the other thread, there is no majic resonant length, i have stated several times that the gamma allows you to tune for low vswr within a wide range of central monopole and radial sleeve lengths,
as you bring the radials closer to the central monopole the resonant frequency goes up and transmissionline mode impedance comes down, element lengths need lengthening in order to maintain resonance at your start frequency but that is not what concerns us, we tune for best signal strength at distance while maintaining a low vswr with the gamma, the information is out there in my own and others posts, if you dont understand it then ask, smartass remarks about saturns rings tell me you either cant understand what you read or dont bother reading what has been written, we are hiding nothing,
the sigma style antenna is tuned with steady fm signals at distances of over 50 miles, central monopole length and radial length are adjusted while monitoring reliable stable signals, at the same time you must maintain a low vswr through gamma rod and strap tapping point adjustments, as you make adjustments you will see that signal strength and bandwidth changed but you can still maintain a low vswr over a wide range of element lengths, you need stable conditions and a means to see small changes in signal, a dmm connected to the radio's s-meter signal works a treat, i use a fluke87 in relative mode and a large external s-meter, i also have a precision 50ohm attenuator to measure any change in .1db increments, it must be done without strong signals pumping your receiver agc, i hope this clears up how i tune the sigma style antenna.
the info on sleeve antennas how they work and how they are steerable is on the net and in the arrl publications,
i dont get sick and tired of people that cant understand what the design is and how it works, its not a simple antenna to understand,
i dont get sick of people that get involved in sigma4 threads claiming a 5/8wave beats the sigma4 even though our many tests and a few i know of in the usa report that the sigma style beats their i10k when mounted at the same feedpoint height,
i dont get sick of people that post hearsay in argument against what is clearly outlined in the patent claiming the sigma is a 1/2wave or j-pole of inferior performance to a 5/8wave but fail to post any technical article to back up the claim or an alternative method of operation to my modified open sleeve antenna theory,
CEBIK told me that style antenna often generate pages of meaningless argument because its mode of operation is not apparent to most people, since CEBIK said that what i was claiming in my adjustments and observations was very much possible and that such an antenna will outperform any groundplane antenna because of the none apparent colinear effect, i presume the people it is not apparent to are the people that think the sigma is a j-pole and inferior to a 5/8wave groundplane,
my claims fit the claims clearly outlined in the avanti patent , they fit what CEBIK told me, they fit every field test we ever did, no single element vertical ever equalled or beat the sigma style antenna at any location/height we tested at,
tuning correctly is everything to antenna pattern/radiation angle in that style antenna in the same way that having the correct relative lengths and spacings of two fighting sticks on a burb is critical to maximum forward gain or maximum front/back ratio whichever you choose to tune for,
mark, the misinfo is comming from the 5/8wave camp, not so much deliberate i hope but a simple lack of understanding and a propensity to belive hearsay rather than well documented antenna principles, while i agree that freecells posts are far from dipolomatic i can understand how peoples reluctance to learn while been happy to post nonesens about j-poles could frustrate him, what you say is in direct conflict with the patent and many tests,
if anybody is genuinely interested in the design read all you can find on open sleeve/skelleton sleeve/skirted monopoles and their derivitives, the information is there if you take the time to find it and digest the information.
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Post by bob85 on Nov 9, 2009 14:59:56 GMT -5
sandbagger, build a j-pole, test it against 5/8waves and a vector 4000, see the answer with your own eyes. at distance you can talk to people that are not workable on a 5/8wave or a j-pole, the sigma style antenna can be adjusted to give better performance than a 5/8wave on a hill or in a valley.
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Post by bob85 on Nov 9, 2009 17:42:55 GMT -5
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Sandbagger
Administrator/The Boss
Posts: 6,245
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Post by Sandbagger on Nov 9, 2009 19:37:50 GMT -5
sandbagger, build a j-pole, test it against 5/8waves and a vector 4000, see the answer with your own eyes. at distance you can talk to people that are not workable on a 5/8wave or a j-pole, the sigma style antenna can be adjusted to give better performance than a 5/8wave on a hill or in a valley. I'm not the one who doubts the S4. I had one and it worked better than my 5/8th wave. Unfortunately, I no longer live where I did in the 70's and 80's when I did my signal comparisons, so anything I might do now, would need a new set of reference data for a proper comparison.
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Post by ic751a on Nov 10, 2009 1:16:24 GMT -5
OK let me come clean; I was intentionally trying to get a rise out of the Sigma IV groupies because I find the truth comes out when poked in the ribs even lightly if the camp in question is only stroking their own egos, and I was expecting tempers to flare ...they didn't and I'm doubly impressed. Initially impressed because those of you who replied kept it polite as the day is long, and secondarily because I'm now interested when you begin to imply that known physics can be manipulated to achieve positive results rather AGAINST the book! So what I gather is, lengthening both the cone and the radiator of an initial 3/4 wave Quasi-J-pole whilst maintaining ~50ohms will achieve a net gain in near-horizonal radiation energy - I like it. Evidently simply making a 3/4 wave J-pole, (which it seems & sounds like what I had in the LW-150) is the easy way of making a cool looking bigger-is-better antenna which is sure to find it's niche, garnering it's share of the market $$, whereas working it until the high-gain / low angle antenna begins to hatch from it's 3/4 wave shell is the trick. OK, so, who has done this and what exactly are your measurements? It would seem it's time for someone to begin to market a real Skelton-pole. Thank you for your time, energy and patience, I'm just now beginning to imagine plans for renewed antenna testing enthusiasmismz. I would like to build mine from scratch, has anyone a close-ballpark measurement or design dimensions for this Skelton-pole? 73[/color][/size]
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Post by mark on Nov 10, 2009 11:03:14 GMT -5
Yes now we are getting somewhere... I have at this very moment a total scratch built Sigma IV laying out here in my yard. I too would like to see some guideline dimensions to help me optimize this antenna. I used 6063 + S/S hardware and made my bottom hub on a lathe and did everything first rate. It does tune up fine but before I put it up I would like to see some details which may help. The 6063 reinforced really makes this antenna stand up nice! I never did like the super flexy versions and especially the Sirio as the thing was like a fly rod with a 15lb fish in even a light breeze.
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Post by mark on Nov 10, 2009 11:11:12 GMT -5
OHHHH!! I forgot to mention that the Avanti guy I talked to said the 5/8 did outperform the Sigma IV at their test range which was measuring vertically polarized signals at 40 feet above ground (if I remember right)... Also he said the notion of the Sigma having more gain than the 5/8 GP was them utilizing the total length as a 3/4 wave antenna for CB marketing reasons... I think what I need to do is see if I can call the guy on the phone and ask him to answer again all these questions and give the background for the antenna and then post the audio file here on Grumpy's. I think it would be informative and interesting for everyone to hear this for themselves. He did not deny that it was a good antenna at all, in fact he said it was very good, but he also said the dimensions were super critical for good performance (as has been said for many years)...
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