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

[davev8]

As per the title, all the photos are in the link
I did some googling some time back and found no info on how a coil between a 1/4 wave section and a 5/8 wave section will give the necessary 180 degrees of delay or if a coil can be used this way to make it work as a collinear
as we know a 1/4 wave antenna doesn't need a matching device nor does it if you lengthen it every multiple of a 1/2 a wave is 1/4 wave then 3/4 wave and so on
this antenna is 7/8 long overall.. is not the coil making it act like a 1-1/4 wave as far as matching is concerned by just adding inductance and nothing else
if the coil is giving it 180 delay its a cunningly simple design where a sample coil matches it to a 50 ohm and makes it a collinear at the same time
link

G-MAX - 10/11 meters antenna for Radio Amateurs

Grazioli G-MAX is a Ground Plane Collinear antenna for the 10 or 11m band. Extremely robust, high performance and with a very low radiation angle.

www.grazioliantenne.com

 

[The DB]

is not the coil making it act like a 1-1/4 wave as far as matching is concerned by just adding inductance and nothing else
if the coil is giving it 180 delay its a cunningly simple design where a sample coil matches it to a 50 ohm and makes it a collinear at the same time
link

Inductance and capacitance have the effect of changing phase. It is literally their only job when it comes to antennas. This effect, however, has a wide range of uses, from shortening 1/4 wavelength antennas (possibly the most common use) to antenna matching. Changing the phase in this antenna is actually a combination of both of the above, although definitely less for matching than phase correction.

The model in the link you provided shows it is actually less than 180 degrees of phase change, which has me curious why they said it was a full 180 degrees. I would say it was closer to 1/4 wavelength of phase change, not the 1/2 wavelength they claim. The bottom element is also closer to 3/8 wavelength long electrically. When it comes to phasing, this length would match much better to the 5/8 wavelength element above. If this were a true 180 degree phase change you would have a 1/2 wavelength element on the top and a 1/4 wavelength element on the bottom, to get from the claimed 5/8 wavelength section to the claimed 1/4 wavelength section you would need 3/8 (or 135 degrees) of phasing, not 180...

I should also point out that inductors aren't the only way achieve the change in phase this antenna has, capacitors can do it as well, as well as phasing stubs, and all three of these methods will end up with a very similar feed point impedance, which calls into question the mentioned "second function" they mentioned.

The radiation pattern does look like a typical co-linear pattern, and it doesn't appear that the antenna is mounted that far above the earth either, although its length may be a bit deceptive here as it is close to 30 feet long if not a little longer so its probably at least that high above the earth in said model, although it does not include a mast, which depending on the situation can either help or hurt the radiation pattern.

I also like the fact that it can be direct fed without having to go through any matching circuits that antennas longer than 1/4 wavelength in length typically need. I think this is actually a bigger deal than most realize, and because of this it wouldn't surprise me if this antenna could handle far more than the 5kW of power the claim.

If you can get a structure that can handle that antenna at about 30 feet or so above the earth, I think it would do amazingly well, but its not going to be cheap...


The DB

 

[davev8]

Thankyou for your reply ..the more i learn the less i know..
price is 290GBP in the UK inc delivery for reference a Sirio gain master is 160GBP and a Sirio new vector 4000 is 130 from the same vendor
if the top of the G-max was at the same height as a vector 4000 do you think it may outperform it ?..if I had one I think i would have to have the feed point a little lower as I am pushing the length of the stub shaft on my tower with the V4K which is 18 inch longer than standard...its bit over 60 feet ar the feed point

 

[bob85]

2 guys have the g-max up that I talk to,
one has a sigma4 & g-max up,

With one guy I see no change in his signal over his imax but I don't know how either are / were installed,

The other guy is my buddy 22 miles from me atcf,
He has mr coily 5/8 vortex Avanti & most other good antennas,

The sigma4 & G-MAX are installed at about the same height to base of antennas, In A/B testing his signal on the g-max is a little stronger than his sigma4 to me,

I think G-MAX is better built than the old 5/8 over 1/4wave BIG-MAC which also had an edge over any of the shorter antennas,
I don't expect them to withstand very high winds.

 

[AudioShockwav]

2 guys have the g-max up that I talk to,
one has a sigma4 & g-max up,

With one guy I see no change in his signal over his imax but I don't know how either are / were installed,

The other guy is my buddy 22 miles from me atcf,
He has mr coily 5/8 vortex Avanti & most other good antennas,

The sigma4 & G-MAX are installed at about the same height to base of antennas, In A/B testing his signal on the g-max is a little stronger than his sigma4 to me,

I think G-MAX is better built than the old 5/8 over 1/4wave BIG-MAC which also had an edge over any of the shorter antennas,
I don't expect them to withstand very high winds.

Hello Bob, it's been too long since we have seen you.
Hope everyone is well at home.
73
Jeff

 

[davev8]

2 guys have the g-max up that I talk to,
one has a sigma4 & g-max up,

With one guy I see no change in his signal over his imax but I don't know how either are / were installed,

The other guy is my buddy 22 miles from me atcf,
He has mr coily 5/8 vortex Avanti & most other good antennas,

The sigma4 & G-MAX are installed at about the same height to base of antennas, In A/B testing his signal on the g-max is a little stronger than his sigma4 to me,

I think G-MAX is better built than the old 5/8 over 1/4wave BIG-MAC which also had an edge over any of the shorter antennas,
I don't expect them to withstand very high winds.

Hi Bob that is useful info. Until I made the thread i did not know if the G-Max was real. or marketing BS, although I am not thinking of replacing the V4K any time soon
so would the new V4K be a little better than your mate's sigma4 and match the G-Max?
i think the trick for antennas' survival in high winds is to have them on a flexible pole that can sway ..my V4K survived the 75MPH winds from the 2020 Storm Ciara here on the Lincolnshire cost with only a broken eye on the end of a radial that I think was a manufacturing defect..i did do a vid beefing the basket up very easily if any ones interested I will post a link ..
.i think I may be in range of you Bob, I am 6 miles north of Skegness

 

[AudioShockwav]

Interested, go ahead and post the link.

73
Jeff

 

[Blackcat630]

Any "Beefing up" info would be appreciated. I'm thinking of trying out a V4K this spring when I make some antenna changes. It would be at 50 ft to the base. It's durability and strength have been the only factor discouraging me from purchasing one.

 

[davev8]

Interested, go ahead and post the link.

73
Jeff

here you go

 

[davev8]

Any "Beefing up" info would be appreciated. I'm thinking of trying out a V4K this spring when I make some antenna changes. It would be at 50 ft to the base. It's durability and strength have been the only factor discouraging me from purchasing one.

what i did off the bat to mine was throw away the self-tapers that hold sections together slot the tube and use hose clamps, i also used penny washers to bolt the ring together as in the video i posted i also taped at every joint Heverly which i think it helps with mechanical strength like where the plastic cross brace connects to the radials i think its stops things rubbing together and wearing out over time. for me the jury is out on the use of self amalgamating tape ..on my V4K it was the 1st time i used it, it was quality 3M tape and had only been on for 2 or 3 years when i did the repair in the vid ..BUT although it sticks to its self very well it did not stick to the antenna that well where there are tight radiuses, there was some corrosion underneath it ..in contrast to a 5/8 wave i made 40 years ago that the remains have been lying on the floor outside at the back of my shed all this time when i wanted a house clip from it after all this time the good quality electrical tape had kept it more or less corrosion free ..i also think antennas survive the wind better if they are not solidly mounted and are on a poll long enubhf to let them sway ... the top of my antenna will lean over 90 degrees in 45MPH+ wind in fact when we had 75MPH winds and it was mounted at the back of the house I could but my back to the frount house wall look up and see the tip of ther anteena bobing into vaiw over the house!! ..that main radiator its still strait after 5 or 6 years on the Lincolnshire coast.. it was up 45 feet but this is the second winter that its 60-65 feet to the feed point i did recently have the top section snapped off but that was because i lengthened it 18 inches..i did make a vid of the repair but it is still on my phone i have not uploaded it yet

 

[bob85]

Hello Jeff, me and my other half are doing ok, just getting old, hope all is well at your end,

Dave, The G-MAX is real it is a 32ft+ collinear & does seem to have an edge over the vector style antennas, not enough to make me rush out & buy one,

The downside of compressing your doughnut for more gain is the antenna & mast need to be stiff otherwise you tend to look like a mobile station if the wind is blowing,
Not sure if I can reach near skegness to be honnest,
I only have a gainmaster up at 35ft to base, still waiting for a man bringing me some ali scaff poles to raise it higher,

I cut down 2 vectors for 6mtrs, now im making one for 4mtrs when I find some teflon tube for the gamma & decent socket to replace the sirio socket.