New thread to debate V-4000

[Shockwave]

There's a polarization wave reversal every half wavelength or quarter?. In a way it reminds me of my X-Dipole(Circular Polarization) antenna thread. The upturned radials would be radiating on the reverse wave by the time the positive/forward half wave/quarter reaches the top of the Vector. Correct me if I'm wrong but that's how I'm seeing it with my mind's eye.

The phase of current will reverse every 1/2 wavelength along a radiator. What is not apparent to some is that the phase of the vertical allowed to radiate has already been delayed by 90 degrees with respect to the source because the cone has confined it.

When we add the 90 degree phase shift and extra 1/2 wave element, we have really matched the phase of the top section to the phase of the cone and half of the original vertical extending above the cone. Using a full 180 degree shift would cause 50% of the added 1/2 wave to buck the phase of the cone.

 

[Lil'Yeshua]

The phase of current will reverse every 1/2 wavelength along a radiator. What is not apparent to some is that the phase of the vertical allowed to radiate has already been delayed by 90 degrees with respect to the source because the cone has confined it.

The radial bottom attachment point is where the reverse current phase enaminates from. The gamma match to vertical radiator is still within the radial basket. How's does this figure in?

 

[Lil'Yeshua]

The radials are a certain length so there is a delay before the forward phase begins. That would give it time to not cancel itself.


Or not.
I was thinking in element length but wouldn't the entire reverse phase continue the radials?


I'm still in the nursery on this.

 

[Shockwave]

I was thinking in element length but wouldn't the entire reverse phase continue the radials?

Only on the inside surface of the radials will you find the currents inverted with respect to being constructively phased. CMC flowing on the outside of this cone provides in phase radiation currents.

 

[Marconi]

how are you modelling the antenna eddie? real transmissionline or mathematical model in eznec?
this guy claims the mathematical transmissionlines built into the program won't radiate unless its a two wire balanced line used into unbalanced loads,


http://www.eham.net/ehamforum/smf/index.php?topic=32091.0

Bob, I don't recall if I've added a feed line to my S4/NV4 models when attempting to try and support my opinions for this design, or not. I know I didn't add a feed line to the loaded 1/4 wave radiator inside the cone "demo" model I just posted. I'm not even sure it is a sound idea, but it came to mind and when I tested the idea the model showed almost ZERO gain with a match showing near 0.00x ohms of resistance and about 43 ohms of reactance, so I decided to try and use it as a demo.

When I do add a feed line to a model I'm guided to use the three wire idea along with the Eznec transmission line feature. Here is page 83, from the Eznec Manual explaining the feature.

IMO, this feature will not work using coax without including the 3rd line and you can read the rest of what it says in that regard, where it is described what can happen if the antenna shows CMC's or not.

One thing I might have done by mistake is to leave or make this 3rd wire larger than the feed line I attempt to add. For example if the model has a mast that connects near the feed point and that diameter is .75" or 1" I might forget to change the mast diameter to that of the feed line used. I also have not checked what difference that might make either, but I'm sure there will be some difference.

Another thing is when I have a model that shows CMC, we can see evidenced for such currents on a mast if included. So we can get a notion from a model that has CMC even without using the TL feature...just like we understand in the real world.

If you check one of my S4 models that is mounted 32' above average Earth you will see there is very little difference between the out of phase currents at the feed point...so we don't see much CMC even though we can assume all end fed vertical monopoles can and do produce some magnitude of CMC's.

BTW, did the report I posted give you any incite into your predictions for what happens as we increase the length of the S4/NV4. I did the report using both 90.5" radials and 107" radials and I was going to do the model with the feed point at the base of the radiator, but I got tired and did not finish.

Again, I hope I am clear in this...whether we agree or not.

 

[Shockwave]

The radial bottom attachment point is where the reverse current phase enaminates from. The gamma match to vertical radiator is still within the radial basket. How's does this figure in?

Apparently the location of the gamma inside the cone does not impact performance. Sirio's CX line of antennas actually places the gamma match inside a solid large diameter aluminum tube that forms the base section in the higher frequency versions.

 

[Lil'Yeshua]

Apparently the location of the gamma inside the cone does not impact performance. Sirio's CX line of antennas actually places the gamma match inside a solid large diameter aluminum tube that forms the base section in the higher frequency versions.

If the vertical radiator is 3/4 wavelength long then a half wavelength long forward phase exists on the vertical on the first phase then the reverse phase excites the radials while there is a quarter wave delay on the vertical radiator before the next forward phase begins. ???



http://www.sirioantenne.it/docs_download.php?file=ID-075_09-04-2008.pdf


Or does the forward current phase excites the entire vertical radiator at the same time?

 

[Shockwave]

If the vertical radiator is 3/4 wavelength long then a half wavelength long forward phase exists on the vertical on the first phase then the reverse phase excites the radials while there is a quarter wave delay on the vertical radiator before the next forward phase begins. ???




Or does the forward current phase excites the entire vertical radiator at the same time?

Wow, you're asking some very good questions! I have always expected as you move away from the feedpoint that we would find a nice 1/2 wave current node beginning at the feedpoint. If you pay attention to the CST model you will note this very much expected behavior is not at all what we see taking place.

For some reason beyond my ability to explain (and EZNEC's too) this design creates its first current node along a short 1/4 wave and not the anticipated 1/2 wavelength of current. This can only be because the upward swept radials are having another effect we have not yet explained.

PS: I just remembered that when you extend a radiator beyond 1/2 wavelength that the current inversion begins at the feedpoint. Just like a 5/8 wave has an 1/8 wave of inverted currents at the base. The difference here is the out of phase base current is extended to 1/4 wavelength and when the radials are also 1/4 wavelength and folded upwards, it created the "non apparent collinear" effect Cebik talked about.

 

[nosepc]

Gamma match devices have great power lost by radiation unwanted.
They do not work as part of the antenna impedance are only couplers.
Are undesirable elements in the antennae, but necessary for coupling
Make them great for dissipating heat, but the loss is directly proportional to its size.
They generate capacitive reactances changing the pattern and antenna efficiency negatively

 

[Lil'Yeshua]

One of the guys on that Eham article I posted suggested dropping the Eznec in favor of the CST program in order to explain this antenna's mode of operation. I'm not familiar with that one yet.

 

[Shockwave]

You just love to try and mislead people Nosepc. If your gamma matches get hot because they have loss, try switching the dielectric insulator to Teflon and watch the loss and heat go away.

Lil'Yeshua, whoever suggested using CST to model the Vector has probably already came to the same conclusion that anyone else needing an accurate model of this design has. Only CST has been able to produce results that resemble the field tests thus far.

 

[nosepc]

You just love to try and mislead people Nosepc. If your gamma matches get hot because they have loss, try switching the dielectric insulator to Teflon and watch the loss and heat go away.

Lil'Yeshua, whoever suggested using CST to model the Vector has probably already came to the same conclusion that anyone else needing an accurate model of this design has. Only CST has been able to produce results that resemble the field tests thus far.

You try to deceive people.
Since the size of the gamma-match no matter why not put a tantalum capacitor instead of such adapter that does not melt everything?

You need a large adapter to dissipate much power lost.

 

[bob85]

i think i understand what your model shows eddie,
i don't dispute the original was too long with the 90" sleeve, the 5/8 j-pole models also show worse performance than a conventional j-pole, even the 5/8 super-j,
i won't be shortening my sigma to exactly 3/4wave until im ready to lose a little signal im my yard, i can't explain why that is at the moment,

with regards to nec,
i would like to understand how it sees the cone,

if eznec has no function for radiation from transmission-lines with cmc unless they are two wire balanced lines with an unbalanced load which can be modeled as two parallel wires like a j-pole,

how will the mathematical model built into eznec include any common mode there may be on the outside of the 4 radials which looks to me like what cst shows?

i can see it working with a regular j-pole evidenced by cebik's j-pole article which is a balanced line feeding a 1/2wave radiator, and plenty more j articles,

so what happens when you make it an unbalanced situation by adding the extra radials, does it then ignore any cm radiation from the lower 1/4wave in its gain and pattern calculations,
making the model a 1/2wave elevated 1/4wave higher above ground?

sirio claim the same 4.15Dbi gain for all their 3/4wave sleeve antennas,

imho that's not possible for a 1/2wave antenna in free space unless its packed with Dilithium crystals,

can you add extra wires to simulate the outside of the radials to give any cm current somewhere to flow as suggested in the link?.

 

[Robb]

He looked right at it but could not see it.

Oh well . . .

 

[Shockwave]

You try to deceive people.
Since the size of the gamma-match no matter why not put a tantalum capacitor instead of such adapter that does not melt everything?

You need a large adapter to dissipate much power lost.

Lets get back to reality NoSee. The Sirio line of CX antennas uses a match that has no capacitor on the same type of antenna design. The loss you assume is present due to capacitive reactance has no improvement in performance with this design. It holds no more power and has no more gain than the Vector even though the matching network has no capacitive reactance.

My clients run 3 kw at VHF into the antenna continuously with no heating of the Teflon gammas. In fact they are weather sealed in heat shrink tubing that would melt right off if RF heating was taking place at this power level.

RF heating is never a problem in a well designed Teflon insulated gamma. The first failure is always related to RF breakdown voltage of the insulator used and not the current or heat. Please get some experience before you attempt to teach others.