Question on the Vector

[Marconi]

The total length of the folded conductor used in the phasing stub you show in this example is 38 inches. That is almost the exact length of the 1/2 wave radiator above it. This phasing section may be a physical 1/4 wavelength however the electrical path is 1/2 wavelength and creates a 180 degree phase shift between its input and output.

I put 27.205 mhz into the calculator and the result for the phasing stub shows about 103" inches. Do you think that means to double it over?

A J-Pole has a 1/4 wave tuneing setup at the bottom like the Vector, why would it be different if made collinear. Since it showed the stub was only 103" I figured the thing was a 1/4 wave like you were claiming for the S4. Did I read it wrong?

Maybe I did read it wrong, the picture indicates a 1/2 wave phasing setup.

 

[bob85]

that's it eddie the equivalent circuit fig 8,
can you explain what cox means by Za & Zt splitting the antenna into two modes of operation ?

 

[Marconi]

Sorry Bob, I could study it a bit and maybe make a wild guess. What do you think it means?

When I originally read this I thought it might have something to do with the 3/4 wave ground plane antenna with horizontal radials vs. one with the radials raised up. That is what happens with my Eznec models. Zt looks to be at the base, and Za looks to be higher up in the image and I thought maybe that was referring to the gamma circuit maybe.

 

[bob85]

theres no gamma on the open sleeve antenna eddie,

what i think cox means is,

you have two sets of currents, antenna mode and transmission-line mode,
how much current flows in each mode is determined by the impedances Za & Zt which determine currents Ia & It flowing in the antenna,
total current flowing into the antenna is Ia + It,

he talks about it everywhere in the article,

"However, at the resonant frequency of the
sleeves, the impedance of the central monopole
is that of an end fed half-wave monopole and is
very high. Therefore IAis small. If proper element diameters and spacings have been used to
match the transmission line mode impedance,
ZT, to 52 Ω; then IT, the transmission line mode current, is high compared to IA"


if that's not how you read the article eddie please explain your how your single current idea fits in with what is claimed.

can you explain this claim using your single current total cancellation equation eddie ?

"At length ratios approaching 3:1, the antenna mode and transmission line mode impedance become
nearly equal again, and the central monopole again carries a significant portion of the antenna current. The radiation from the top 1/2 λcombines constructively with the radiation from the 1/4-λsleeve elements to
produce gains of up to 3 dB more than just a quarter-wave vertical element alone."

where did cox go wrong eddie ?
did he misunderstand H. B. Barkley who in his paper ( H. B. Barkley, The Open-Sleeve As A Broadband Antenna ) gives a more detailed explanation of the antenna,

reminded me of what cebik told me when he says

"The problem here is somewhat more complex, however, since the effective termination of the transmission line mode is not immediately obvious and the division of the antenna
mode currents is difficult to determine theoretically."

i almost had a shockwave arriving on wwrf moment when i read this eddie

"One method of increasing the resistive term of each transmission line is to increase the effective resistive end loading or radiation losses, by a greater parasite spacing.
This greater spacing has a detrimental effect on the reactance term, but the resistance can predominate for spacings greater than a certain minimum (as it apparently did in the theoretical curve) There is a maximum limit to the spacing usable., above which the low frequency behavior suffers, or severe pattern distortion occurs.

An alternative method may be to flare the parasites outward from the dipole, increasing the losses of the transmission line mode by radiation.
This, of course, is essentially reverting to the idea of the gradual taper to free space as a means of achieving broadbanding but the explana tion of the resistive loading of the transmission lines originates the suggestion.

However, the taper appears to destroy the analogy to the antenna mode of operation, so that analysis by the present theory would be questionable, and the results of this technique would most readily be determined experimentally,

One further means of increasing losses is by a reduction of parasite diameter, but some intrinsic broadbanding effect would undoubtedly be lost."

do skinny flared radials around a fat central monopole remind you of anything eddie ?

 

[Shockwave]

Marconi, the only way I know to tell if your model gets the phase correctly is the use of my 4 wire test. I don't believe anyone has corrected that problem yet. I think DB has done similar experiments in EZNEC to attempt to correct this phase and was able to show decent gain in his latest model. Unfortunately he still confirmed EZNEC only worked when the collinear model used a 180 degree phase delay in total contradiction to all field tests.

In the rare event you are able to get EZNEC to model a Sigma, you have the information to confirm it yourself now that I've explained it. I can't tell without adding the 4 wires. You need to run that test on your own model. When you can stretch the 3 wire folded phasing section out in a straight line and it measures close to a 1/4 wavelength over its ENTIRE conductor length, you will be the first ever to make EZNEC work with the Sigma.

Since the shorted phasing stub in the J-pole example is known as a "1/4 wave stub" even though it produces a 180 degree phase shift and has a conductor length of 1/2 wave, I will no longer refer to this type of phase delay by its insensible wavelength name since it's misleading, confusing and not accurate. I think it's inappropriate to name a phase delay based on its physical length AFTER the conductor is folded in half rather than to name it based on the actual amount of shift in wavelength or phase it produces.

 

[The DB]

Just a correction Donald, it was 4NEC2, not EZNEC. They are based on the same engine, but I'm not sure if EZNEC uses a modified NEC2 or if it is stock.

I have played with EZNEC some, the layout of EZNEC just seemed un-intuitive to me... With 4NEC2 I was able to essentially jump right in.


The DB

 

[Marconi]

Marconi, the only way I know to tell if your model gets the phase correctly is the use of my 4 wire test. I don't believe anyone has corrected that problem yet. I think DB has done similar experiments in EZNEC to attempt to correct this phase and was able to show decent gain in his latest model. Unfortunately he still confirmed EZNEC only worked when the collinear model used a 180 degree phase delay in total contradiction to all field tests.

Donald, whether Eznec does or doesn't work like I've suggested or not...this consideration to connect the wires correctly over user friendliness in data entry, will not improve the antenna performance like you might be expecting.

As I've noted, all performance figures remain the same either way. If Eznec has another flaw...then it will need additional understanding to resolve.

DB, can I ask you again...do you see something similar in handling your wires using 4Nec2, like I've reported here using Eznec?

BTW, I think there are numerous versions of how NEC products may be made available to users.

 

[Lil'Yeshua]

The basket; just my thoughts.
http://en.m.wikipedia.org/wiki/Inductance

 

[Marconi]

theres no gamma on the open sleeve antenna eddie,

what i think cox means is,

you have two sets of currents, antenna mode and transmission-line mode,
how much current flows in each mode is determined by the impedances Za & Zt which determine currents Ia & It flowing in the antenna,
total current flowing into the antenna is Ia + It,

he talks about it everywhere in the article,

"However, at the resonant frequency of the
sleeves, the impedance of the central monopole
is that of an end fed half-wave monopole and is
very high. Therefore IAis small. If proper element diameters and spacings have been used to
match the transmission line mode impedance,
ZT, to 52 Ω; then IT, the transmission line mode current, is high compared to IA"


if that's not how you read the article eddie please explain your how your single current idea fits in with what is claimed.

can you explain this claim using your single current total cancellation equation eddie ?

"At length ratios approaching 3:1, the antenna mode and transmission line mode impedance become
nearly equal again, and the central monopole again carries a significant portion of the antenna current. The radiation from the top 1/2 λcombines constructively with the radiation from the 1/4-λsleeve elements to
produce gains of up to 3 dB more than just a quarter-wave vertical element alone."

where did cox go wrong eddie ?
did he misunderstand H. B. Barkley who in his paper ( H. B. Barkley, The Open-Sleeve As A Broadband Antenna ) gives a more detailed explanation of the antenna,

reminded me of what cebik told me when he says

"The problem here is somewhat more complex, however, since the effective termination of the transmission line mode is not immediately obvious and the division of the antenna
mode currents is difficult to determine theoretically."

i almost had a shockwave arriving on wwrf moment when i read this eddie

"One method of increasing the resistive term of each transmission line is to increase the effective resistive end loading or radiation losses, by a greater parasite spacing.
This greater spacing has a detrimental effect on the reactance term, but the resistance can predominate for spacings greater than a certain minimum (as it apparently did in the theoretical curve) There is a maximum limit to the spacing usable., above which the low frequency behavior suffers, or severe pattern distortion occurs.

An alternative method may be to flare the parasites outward from the dipole, increasing the losses of the transmission line mode by radiation.
This, of course, is essentially reverting to the idea of the gradual taper to free space as a means of achieving broadbanding but the explana tion of the resistive loading of the transmission lines originates the suggestion.

However, the taper appears to destroy the analogy to the antenna mode of operation, so that analysis by the present theory would be questionable, and the results of this technique would most readily be determined experimentally,

One further means of increasing losses is by a reduction of parasite diameter, but some intrinsic broadbanding effect would undoubtedly be lost."

do skinny flared radials around a fat central monopole remind you of anything eddie ?

Bob, I missed seeing this post earlier.

This is breath taking new information, and I will not even reply for fear I would just confuse this message for all other's looking in.

I read my Eznec Manual that is right at 200 pages, front and back, twice all the way through, but this has got to top that I one...for what's necessary to really understand how the Sigma 4 works. How can I thank you.

This puts to shame Donald's simple idea that a 1/4 wave length radiator can produce a 1/2 wave pattern.

 

[Marconi]

The basket; just my thoughts.
http://en.m.wikipedia.org/wiki/Inductance

Lil'Yeshua, like with Bob's startling last report, I won't respond to this report either. I fear the contents might be confused for others, by my shamefully primitive remarks.

 

[Marconi]

theres no gamma on the open sleeve antenna eddie,

Bob I know you don't care, but my point was I was guessing that there might be a reason for a gamma if the radials were set closer that a 1/4 wavelength away for the base of the monopole, like the antennas we are talking about.

Why does it piss you off that I tell you when I don't understand something? Does everything have to be about our pride in expression.

I tried telling you already that when I first read that article I thought that discussion, your Fig 8, was talking about tuning the antenna...either at the base or farther up the antenna.

 

[Marconi]

The basket; just my thoughts.
http://en.m.wikipedia.org/wiki/Inductance

While I was considering all this information, I was on the watch for the edit done a month ago by anonymous.

In the gist of it all, I took away that the cone was nothing more than a tuning device that also helps block the out of phase currents for a 3/4 wave radiator that ill-effected the pattern by distortion due to horizontal radials, and worked just like a J-pole, but did it a little better. The big advantage is the extra height gained by raising the current maximum up higher than other shorter wavelength antennas.

Thanks.

 

[Marconi]

Bob, if you get tired of listening to me, try this instead. Maybe it will mellow you out a bit.

Daryl Hall and Chromeo doing Tenderoni



or Daryl and Johnny Swim doing Do What you Want

 

[bob85]

eddie,
my grandpa always told me that if what somebody says upsets you then you must value their opinion,

it does not piss me off when you don't understand something eddie, i find it amusing, your convenient nv4k comment brought tears to my eyes,
i was thinking maybe somebody put a broken gramaphone needle in your NovoPen ?

im here to get to the bottom of it eddie, no axe to grind no sales to make no antenna builder buddies to please no lies to tell ect,

i have posted a possible method of operation, did you read that eddie POSSIBLE ,

please post up something of equal detail from a respected source on your version of how it may work so that we may look at the evidense,

otherwise i will refere you to the last lines of this post from almost 6 years ago,
http://www.worldwidedx.com/threads/avanti-sigma4-an-alternative-view-point.31799/

 

[Shockwave]

This puts to shame Donald's simple idea that a 1/4 wave length radiator can produce a 1/2 wave pattern.

The shame is you're too damn hard headed to learn anything or consider field tests that prove your model and ideas cannot be replicated in the field. It's got nothing to do with the simple 1/4 wavelength radiator and everything to do with the PAIR of currents mixing together on that radiator.

You know a pair of currents out of phase by 180 degrees cancels each other but you apparently do not know how they combine when the offset in phase is only 90 degrees. Since the currents are 1/4 wavelength, their ends can be a full 90 degrees out of phase without any portion being deconstructive either.