Is the Grazioli G-Max really a 10/11m collinear? how does a coil delay the signal 180 degrees

[Henry HPSD]

Hello all,

Bob, A while ago i was wondering the same thing... the Austalian collinear...
Then out of nothing when i woke up ... Duoro... that was it.
All I did find was :

DUORO - ANTENNA Sales

KUR02 is the callsign for Kurrajong CB repeater station located at Kurrajong Heights in NSW.

web.archive.org

The antenna is "listed" there, but sadly the page itself doesnt seem to be archived ?

I am (still) thinking about writing an article to publish on the website how one could construct it with some technical back ground etc.
It is on my "bucket" list, but so are a couple other projects hi.

Kind regards, Henry

 

[bob85]

That would be great Henry, I could build a sturdy Highlander with the tubes I have,
DUORO! you nailed it, I will resume my search

I read the case of the curly collinear article from CEBIK,
I don't understand why Grazioli claim the G-MAX is 5/8 over 1/4wave when the lower radiator is much longer than 1/4wave.

 

[bob85]

If anybody needs measurements to model the G-MAX let me know,

here is a link to how CEBIK made his model using equal segment lengths for physical coil & radiators,

The Case of the Curly Collinear

 

[The DB]

here is a link to how CEBIK made his model using equal segment lengths for physical coil & radiators,

Its strange that I don't recall seeing that Cebik article before, I'm pretty sure I read them all at one point or another...

I was never fond of the 5/8 over 1/4 or 1/2 collinear idea. I think part of it was I was worried about how the extra 1/8 wavelength of out of phase currents would mess with the collinear effect...

There is also an optimal length for said collinear sections to be apart, and in most cases, the 1/2 over 1/2 wavelength or 1/2 over 1/4 wavelength setups are naturally very close to said optimal distance between current nodes to begin with. Putting a 5/8 wavelength section on top instead would necessarily push said points even further apart countering any said benefit some people have set in their minds that they would get from using a 5/8 wavelength section, or so I think...

But then I have my own thoughts on what vertical is better for what, and with who I am responding to, I would just be preaching to the choir I think...


The DB

 

[bob85]

DB
I don't like the 5/8wave & its 1/8wave out of phase radiation cancelling some of the benefit it has in raising the upper 1/2wave higher above ground,
There is a better way,

as you say when its the upper part of a collinear that unwanted 1/8wave is also moving the current maxima further apart, I thought that would be a bonus,

ad the fact that the G-MAX lower radiator is about 147" & not 1/4wave
the currents are even further apart,

I was under the impression that optimum spacing for 2 end to end elements is close to .9 wavelength,
The G-MAX seems to be in the ballpark for spacing of current maxima on the two radiators, Less than .5db down from optimum spacing,

am I missing something ?

If I remember correctly Henry's Highlander had about 1/2wave upper radiator with a longer/taller phasing coil & also had a longer than 1/4wave lower radiator.

Thanks

 

[Henry HPSD]

We all want optimum, though i can imagine in regards to a collinear on 27 MHz.. it is more or less not a question of what we would like, it rather is one of what is mechanical possible.

@ Bob, Top part was ...if memory serves me well ...the top part was 6,7 meter.

Grazioli...I noticed the factory beeing very close to the proximity of the one from Sirio. And the name of the company is the same name as the founder of Sirio.
I have always wondered if there is a "connection" between them.

Im impressed if the gain figure provided is over average ground conditions.

I dont like the advertising campain telling things that simply are not accurate.
But then again, we are used to that from manufacturers hi.

I still have the extended double zepp up (for years).
Which does a similair job...not bad for a piece of wire.
Only down side is the supporting mast hi.

Kind regards, Henry

 

[The DB]

As I recall, peak gain was somewhere between 1/2 and 5/8 wavelengths apart, but I could be wrong. I do know there is an upper limit of distance between said current nodes, and I am thinking that 9/10 (i.e. 0.9) seems a bit high. I could be wrong as it has been a while since I've modeled this stuff...

In a 1/2 over 1/4 or 1/2 over 1/2 scenario, you have a physical 1/2 wavelength of antenna (1/4 on the top and 1/4 on the bottom elements) plus the physical size of the phasing mechanism between the two, of which a coil based system discussed in the G-Max (and in your Cebic link) will normally require more of said space that other methods require (depending on the specific design of course)...

All this being said, I do recall the EDZ models comparing very well against collinear models, which makes me question my thoughts on said distance requirements mentioned above...

Unfortunately as I have been bouncing around between linux distros lately I don't have any modeling program loaded, and the one I am currently running wouldn't be the best to load one up in (its an atomic version and will have trouble getting a version of wine going, for anyone who knows what that means...). It would be nice to get a third party model for comparison to the manufacturers...

Any who, on my end I'm calling my data speculation at the moment, as I'm pulling from memory from years ago...

We all want optimum, though i can imagine in regards to a collinear on 27 MHz.. it is more or less not a question of what we would like, it rather is one of what is mechanical possible.

I see how it is, sneaking in a post after I start typing one of my own

I agree with this, more or less. However, I think that people can be creative, and can likely get near as makes no difference if they choose to put out the effort (and maybe money?) even on a band like 11 meters...


The DB

 

[bob85]

Henry,
I have given some thought to an EDZ even the improved EDZ with the capacitors to bring all currents in phase,
at the moment its not practical,
I did encourage a local friend to build an aluminum EDZ for 2mtrs which works great,

With regards to the Grazioli I am not blinded by the advertising campaign,
I boungth it at a VERY good discount from a local friend who assembled it & could not tune it on a short pole, he put it back in the box & asked if i wanted to buy it,

I have been down this collinear road before with the BIG-MAC & remember its pros & cons,

While the G-MAX is better made than the BIG-MAC or SIRIO antennas its still a fair weather antenna,
The radials are whimpy, if I get a buzzard perched on one which is likely its goodnight vienna,

unfortunately the good quality tube I have won't stretch to building a more rugged G-MAX but it may be enough to build a Highlander.

 

[bob85]

DB
I am a patient guy,
an independent model would be very nice but I am in no rush,
no rush to put the antenna up either,

my buddy is talking about putting his G-MAX up higher so we can do some more tests, He likes his G-MAX & he has plenty of decent antennas to compare it to,

My first impressions are that the youtube videos of G-MAX vs xxx are pretty much inline with what I have seen in our tests,

I am on with cleaning up & comparing my two 50mhz vectors to see if removing the ring at the top of the sleeve is beneficial,
my buddy just made a 6mtr dominator from a sirio 827 so we can do some tests.

 

[bob85]

Henry you are right about the Grazioli family connection,

Giuseppe Grazioli founded SIRIO antenne in 1972,
His daughter Stefania & son Pier Francesco worked along side him for over 30 years,

Stefania now manages SIRIO,
after the death of his father Francesco who was SIRIO's product development manager decided to leave & start Grazioli antennas.

 

[The DB]

As I recall, peak gain was somewhere between 1/2 and 5/8 wavelengths apart, but I could be wrong.

I just loaded 4nec2 on by backup installation (something I always keep but sometimes forget I have). It turns out I remembered wrong.

I started with two 1/2 wavelength center fed dipoles in a collinear setup, and I moved them apart 1 foot at a time. Peak gain happened between 17 and 18 feet between them. Factoring in where the current nodes are, that is very close to 1 wavelength current node to current node.

You said you have the dimensions of the antenna? I have some of them from the manual but not all of them, especially that coil, I know it has 9 turns but know nothing else... Also, what frequency is it tuned for with said dimensions?

Here is a chart of the data, the numbers across the bottom are the distance between the two elements in feet, the numbers on the left are gain.

The DB

 

[The DB]

This is an initial look at the 5/8 over 3/8 groundplane collinear concept. My model is not based on the dimensions of the G-Max, although it will be compared to them with my thoughts given as well.

The model I made has a feedpoint impedance of 68.9 - j0.24, which is an SWR of 1.38 and very close to resonance, not bad for an initial look at a design concept...

Also my model is modeled at 1 wavelength above the earth, matching the models from the site. With certain similarities between said models I believe them on this, so I don't think they mounted the antenna super high to overhype said gain.

For reference, this is the data taken directly from the Grazioli antenna site. It is all one image, so I am posting it as is. We will be comparing the middle and right sections of this image.

My current and phase looks similar to the G-Max.

As their current distribution comes very close to my 5/8 over 3/8 design, I wonder where they came up with the 5/8 over 1/4 idea? Using a loading coil, such an idea is possible, but I just don't see why they would say that for this antenna...

Now for the gain...

I get far less gain, and the patterns are different. I'm not 100% sure why yet, and I don't have time to play anymore, have to get ready for work... From what I can tell, the angles of radiation are 1 degree off of each other, so in the regard we are in the same boat. I have far less gain than they do. This could be due to a combination of any number of things, different ground, I used aluminum elements and they used perfect conductors, different dimensions, ect.

This structure is already in the range of 75% efficient, which means 25% of the signal is being lost before the radiation happens. I'm pretty sure that if I adjust the lengths of the upper and lower sections I should be able to pick up more gain, and change the model so that it more closely matches the one they provide, but I doubt there is 2 dB worth of gain to pick up...

When I next get a chance I will have to experiment with using perfect conductors, and with adjusting the dimensions of the antenna.


The DB

 

[bob85]

DB

From the assembly instructions I slotted the tubes in for a frequency of 27.15-27.2mhz,

The measurements I gave are total assemble radiator lengths,
subtract 1" from the lower radiator for distance between feed point tap & lower phasing coil tap,
subtract 1/2" from the upper radiator,

The coil is 9" between the pegs,
9 turns x 116mm or 4.57" between the centers of the coil wire,
wire diameter is 6mm or .236"

If you need anything else let me know,

If 18.1ft is the freespace 1/2 wave @27.15mhz your spacing/gain chart is inline with what w8ji claims.

 

[The DB]

I took the model from above and made the changes as per your posts. Somehow I completely missed the lengths you had already posted on the first page of this thread...

Anyway, I presumed that if I shorten the upper and lower vertical element lengths that gain will go up, and it did. In addition to shortening said elements to your lengths, I also lengthened the coil from 8 to 9 inches to better match the antenna. One day I may or may not actually put the wires in to model said coil directly, but that is a decision for future me...

These changes netted a gain of nearly 1 dB, which was more than I was expecting, but its there. I should note that the original model under reported gain slightly, and this one over reports gain slightly, so there is that to consider, but even with that I am surprised at this change in results... Anyway, here is the model...

This model has a feed point impedance of 52.5 + j 1, which has an SWR of 1.05, so it matches very well. The structure also has a much higher efficiency than the model above, which is where I think most of this gain over that model comes from. It is still 1.1 dB off of the provided G-Max model...

I mentioned that I was using aluminum elements, and not perfect conductors, so to see the difference, removing the "lossy" aluminum elements in favor of "perfect conductors", nets me a whole 0.01 additional dB bringing it up to 5.38 dBi in gain so that isn't the cause of this difference...

Beyond this, I am wondering what is different between their and my models? Like me they seem to be using a lumped inductance, but unlike mine, theirs seems to be much a smaller section that doesn't account for the length of the coil? This can have an effect, but 1.1 dB worth? I highly doubt it.

I guess I can play around with earth settings and see what happens... I'm not sure what else I can to do duplicate their data short of seeing their model data itself and figuring out what else is different?


The DB

 

[bob85]

CEBIK got a little more gain changing to a physical coil, he thought part of that was the increased spacing,

Grazioli make 2 claims for gain,

In the Electrical data it says 5.65 dbi ( no frequency specified )
very close to your model a fiddle with the ground could find the difference or a physical coil maybe,

The model says total gain 6.48dbi @27.5mhz & 11mtrs above real ground,
can ground type do that ?

could be that you are not selling them