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I may be reading the article wrong but it mentions infinite perfect conducting groundplane which is what the 5/8wave proponents use to bolster their claims of gain for a radiator with 1/8wave of deconstructive radiation,

Having a super efficient ground mounted antenna is OK in some situations but its no good if it can't see through buidings & other obstructions for people that live surrounded by obstructions.

According to the arrl antenna books which I quoted in the first post of this thread many years ago
a 3/4wave monopole fed at its base has 1/4wave of out of phase radiation from the lower 1/4wave whereas the open sleeve antenna with its close spaced radials has radiation from the lower 1/4wave that is in phase with the upper 1/2wave compressing the pattern & increasing gain over the simple 3/4wave monopole

The explanation the arrl gives us is that when you bring the radials close to the monopole resonant frequency goes up & impedance goes down,
transmission-line mode currents flow between monopole and radials,

impedance drops because the transmission-line mode impedance is seen in parallel with the 3/4wave monopoles antenna mode impedance,
current flows into that impedance & current flows on the outside of the radials as in phase radiation just like the in phase radiation from the short leg of a J-pole caused by the unbalanced termination of the 1/4wave stub increases gain in the direction of the short leg,

we have not seen any model that shows how much radiation comes from the outside of the cone in the sigma4 because the only model anybody has done is Henry's model that was terminated with resistors & not unbalanced as in the real antenna,

Transmission-lines don't radiate when they are terminated with a resistive load regardless of the load been equal to the characteristic impedance of the line or not,

all we are seeing is a small magnitude of radiation due to the conductors of the cone not been very closely spaced and perfectly parallel to the monopole,

I have asked time and time again if NEC or other software can model the cone in isolation with an unbalanced load replicating the real antenna and thus far nobody has come up with a solution,

Homer why not build a ssfm & compare it to the sigma style antenna,
just make sure you use a quality isolator & not a lossy CB antenna mount like the guy who published the skeleton sleeve fed monopole article,

That would answer how far behind the ssfm a sigma style antenna is if its behind at all.

<blockquote data-quote="bob85" data-source="post: 766882" data-attributes="member: 18">I may be reading the article wrong but it mentions infinite perfect conducting groundplane which is what the 5/8wave proponents use to bolster their claims of gain for a radiator with 1/8wave of deconstructive radiation,Having a super efficient ground mounted antenna is OK in some situations but its no good if it can&#039;t see through buidings &amp; other obstructions for people that live surrounded by obstructions.According to the arrl antenna books which I quoted in the first post of this thread many years agoa 3/4wave monopole fed at its base has 1/4wave of out of phase radiation from the lower 1/4wave whereas the open sleeve antenna with its close spaced radials has radiation from the lower 1/4wave that is in phase with the upper 1/2wave compressing the pattern &amp; increasing gain over the simple 3/4wave monopoleThe explanation the arrl gives us is that when you bring the radials close to the monopole resonant frequency goes up &amp; impedance goes down,transmission-line mode currents flow between monopole and radials,impedance drops because the transmission-line mode impedance is seen in parallel with the 3/4wave monopoles antenna mode impedance,current flows into that impedance &amp; current flows on the outside of the radials as in phase radiation just like the in phase radiation from the short leg of a J-pole caused by the unbalanced termination of the 1/4wave stub increases gain in the direction of the short leg,we have not seen any model that shows how much radiation comes from the outside of the cone in the sigma4 because the only model anybody has done is Henry&#039;s model that was terminated with resistors &amp; not unbalanced as in the real antenna,Transmission-lines don&#039;t radiate when they are terminated with a resistive load regardless of the load been equal to the characteristic impedance of the line or not,all we are seeing is a small magnitude of radiation due to the conductors of the cone not been very closely spaced and perfectly parallel to the monopole,I have asked time and time again if NEC or other software can model the cone in isolation with an unbalanced load replicating the real antenna and thus far nobody has come up with a solution,Homer why not build a ssfm &amp; compare it to the sigma style antenna,just make sure you use a quality isolator &amp; not a lossy CB antenna mount like the guy who published the skeleton sleeve fed monopole article,That would answer how far behind the ssfm a sigma style antenna is if its behind at all.</blockquote>

[QUOTE="bob85, post: 766882, member: 18"] I may be reading the article wrong but it mentions infinite perfect conducting groundplane which is what the 5/8wave proponents use to bolster their claims of gain for a radiator with 1/8wave of deconstructive radiation, Having a super efficient ground mounted antenna is OK in some situations but its no good if it can't see through buidings & other obstructions for people that live surrounded by obstructions. According to the arrl antenna books which I quoted in the first post of this thread many years ago a 3/4wave monopole fed at its base has 1/4wave of out of phase radiation from the lower 1/4wave whereas the open sleeve antenna with its close spaced radials has radiation from the lower 1/4wave that is in phase with the upper 1/2wave compressing the pattern & increasing gain over the simple 3/4wave monopole The explanation the arrl gives us is that when you bring the radials close to the monopole resonant frequency goes up & impedance goes down, transmission-line mode currents flow between monopole and radials, impedance drops because the transmission-line mode impedance is seen in parallel with the 3/4wave monopoles antenna mode impedance, current flows into that impedance & current flows on the outside of the radials as in phase radiation just like the in phase radiation from the short leg of a J-pole caused by the unbalanced termination of the 1/4wave stub increases gain in the direction of the short leg, we have not seen any model that shows how much radiation comes from the outside of the cone in the sigma4 because the only model anybody has done is Henry's model that was terminated with resistors & not unbalanced as in the real antenna, Transmission-lines don't radiate when they are terminated with a resistive load regardless of the load been equal to the characteristic impedance of the line or not, all we are seeing is a small magnitude of radiation due to the conductors of the cone not been very closely spaced and perfectly parallel to the monopole, I have asked time and time again if NEC or other software can model the cone in isolation with an unbalanced load replicating the real antenna and thus far nobody has come up with a solution, Homer why not build a ssfm & compare it to the sigma style antenna, just make sure you use a quality isolator & not a lossy CB antenna mount like the guy who published the skeleton sleeve fed monopole article, That would answer how far behind the ssfm a sigma style antenna is if its behind at all. [/QUOTE]

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