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.
