To 7/8 or NOT to 7/8, that is the equastion

[Needle Bender]

Be careful NB,
i have tried different permutations of beefing vectors up,
adding any extra weight or wind load to the upper radiator makes them even more floppy,
i ended up honing the hub to take an AVANTI radiator,

Slotting to get rid of the screws is a good idea, The screws rot and the holes enlarge with the constant rocking in the wind,

i would use lightweight breeze Aero Seal hose clamps like the i-10k uses & trim any excess band with a dremel,
They are- strong enough and lighter than pressed hose clamps.

Bob, thanks for the clamp brand info! One of my pet peeves is when I tighten a hose clamp to where it's just beginning to squeeze and 'POP!' - now it's junk. Actually always was.
- Good to know of a brand that's hopefully strong enough to handle some real torque!

And one of the options in adding a full 3' length of (metric)1/2" is being able to move each of the other radiator sections down inside a few more inches to help beef it up a bit, hopefully limiting the flex.
I also may add an 8' x 5/8" fiberglass rod into the bottom. 5/8" will still flex but should limit it to somewhere near 1/2 the normal NV4K base flex. I might even use a small piece of 5/8"-1/2" I.D. tubing to couple a 1/2" rod to the top of that 5/8", another 1/2"-3/8" I.D. piece of tubing to couple a 3/8" to the top of that, for increased internal structural rigidity. My chore will be finding metric tubing so the fit is spot-on.

Man NB, posts your results or some readings on an analyzer if you have one please. I would like to see what it does at like 20-25ft to the feedpoint. I can get an idea at least of what to expect. And pics of the upgrades that you do make. It would me much appreciated. I'm at the cross road of just getting another sirio tornado, or to try the vector 4000. I too like the slits and hose clamps which will be done to next antenna as well. Go light weight as possible!!

Well if you can only go 25' to the base, keep in mind the point of max radiation (high current node) is 9' down from the top of the radiator so at 20' (plus 18') it will be very close to 1 wavelength (36') above the ground, not a bad place to have it. I wonder if dropping it 2' might not set it at a sweet spot, depending on your ground efficiency.

NB:
When you say test at 45', do you mean antenna tip height at 45' or is that where the base(feed point of antenna) will be located?

Sorry if I missed this before.

I'm referring to the base where it's mounted to the push-up telescoping mast.

 

[gamegetter]

NB:

i'm not following your reasoning to 222 for his 25' mast installation. Can you explain?

the way i see it, if the radiator is 27 foot long(and acts as an electrical 1/2 wave, then the point you mention for high current node would be at 43' above the ground.

Here is my math:
mast at 25'+tip of radiator at 27'=52'

52'-9'=43'.

i can see your point of the 2' drop if electrically it behaves as a 20' wave. so yes some play there to find the sweet spot.

 

[Needle Bender]

NB:

i'm not following your reasoning to 222 for his 25' mast installation. Can you explain?

the way i see it, if the radiator is 27 foot long(and acts as an electrical 1/2 wave, then the point you mention for high current node would be at 43' above the ground.

Here is my math:
mast at 25'+tip of radiator at 27'=52'

52'-9'=43'.

i can see your point of the 2' drop if electrically it behaves as a 20' wave. so yes some play there to find the sweet spot.

LoL- you lost me somewhere in there. He mentioned a 20'-25' mounting height and I used the 20', plus 2/3 of the NV4K of 18', = 38'. Then I mentioned maybe drop it 2' for a 36' height above ground to the center of the top 1/2 wave where I believe is the point of highest current.

But sometimes simply higher is better.

 

[Road Squawker]

jeez, 33 posts so far, and no one has questioned what an "equastion" is

 

[bob85]

NB
The Breeze all stainless aero seal clamps fall somewhere between those cheap clamps that pop far too easy and the quality pressed hose clamps like jubilee brand & mikalor,
They have never let me down in 9 years of using the i -10k,

Sure you can get stronger clamps like the Mikalor tri torque or the superclamp on the bottom of the vector,
imho the aeroseal are a good compromise between strength and weight for beefing up the vector.

 

[222DBFL]

Thanks NB! Info is much appreciated!! Look forward to your results. And again, thx for the replies. Have a good one.

 

[Marconi]

Attached below are 4 Free Space models with pattern overlays for my 26.8' foot New Vector 4K model with dimensions set to specifications. All I did was change the radiator lengths to the other 3 lengths noted in this thread by Needle Bender for comparison.

31.6' for a 7/8 wave Saliut
29.6' for a .82 wave
27.7' for a .75 noted for the Sigma 4 length
26.8' for a .75 noted for the Sirio NV5K length.

I posted the 4 overlays, one for each radiator length in order to more easily compare the gain and angle results for each antenna being discussed.

The active Primary pattern starts with the 26.8' model and it is noted in black ink. The others are in different colors and are made active using the ( * ) beside the description.

Attached below are the supporting models and overlays. Just click on the file: IMG.pdf

The note "watch this area"... is IMO the area of the antenna that is ill-effected by making the radiator longer than 3/4 wave. It looks to me to be the reason we see the angle go higher when we add extra length to the radiator. I can't explain why these Free Space models show to be contrary to reports by others, but maybe NB will check this trend out for us when he does his real world testing and reports back.

Note: If we just look at the Free Space gain for these models and don't consider the maximum angles they produce...we might get a totally different idea for the results.

 

[gamegetter]

At an elevation of 45' feet to the base from the ground, i would stick with the original avanti sigma 4 design.

For this antenna(sigma4) my cutoff point for mounting would be 25 feet to base.

Anything lower and a 5/8 wave would suffice. The exception being the GM which may be fickle with anything too close. But i like the plug and play of the GM.

 

[bob85]

For me the sigma style antennas work better than any shorter antenna when close to the ground, current maxima is higher & they see over obstructions better,

The gainmaster does seem to not like been mounted near the ground, Mounted on a 14ft pole the GM was a little behind my i-10k,
@20ft its very close to the i-10k,
Maybe if i raised them higher the GM would be in front a little.

 

[Needle Bender]

Attached below are 4 Free Space models with pattern overlays for my 26.8' foot New Vector 4K model with dimensions set to specifications. All I did was change the radiator lengths to the other 3 lengths noted in this thread by Needle Bender for comparison.

31.6' for a 7/8 wave Saliut
29.6' for a .82 wave
27.7' for a .75 noted for the Sigma 4 length
26.8' for a .75 noted for the Sirio NV5K length.

I posted the 4 overlays, one for each radiator length in order to more easily compare the gain and angle results for each antenna being discussed.

The active Primary pattern starts with the 26.8' model and it is noted in black ink. The others are in different colors and are made active using the ( * ) beside the description.

Attached below are the supporting models and overlays. Just click on the file: IMG.pdf

The note "watch this area"... is IMO the area of the antenna that is ill-effected by making the radiator longer than 3/4 wave. It looks to me to be the reason we see the angle go higher when we add extra length to the radiator. I can't explain why these Free Space models show to be contrary to reports by others, but maybe NB will check this trend out for us when he does his real world testing and reports back.

Note: If we just look at the Free Space gain for these models and don't consider the maximum angles they produce...we might get a totally different idea for the results.

Glad you're enjoying this, Marconi, and thank you for your energies! I love your graphs and wonder if the Avanti pattern might not benefit from the shorter cone?
I'm still wondering about that 7/8 pattern & recalling Donald's input regarding EZNEC not being able to correctly deal with the oddities of the cone currents of this NAC design. Or has a newer version been released which now IS able?

jeez, 33 posts so far, and no one has questioned what an "equastion" is

 

[Needle Bender]

migt

At an elevation of 45' feet to the base from the ground, i would stick with the original avanti sigma 4 design.

For this antenna(sigma4) my cutoff point for mounting would be 25 feet to base.

Anything lower and a 5/8 wave would suffice. The exception being the GM which may be fickle with anything too close. But i like the plug and play of the GM.

Agreed, mostly. I'm wondering about your conclusions regarding mounting height for the NV4K. Is this info from Henry's treatise?

For me the sigma style antennas work better than any shorter antenna when close to the ground, current maxima is higher & they see over obstructions better,

The gainmaster does seem to not like been mounted near the ground, Mounted on a 14ft pole the GM was a little behind my i-10k,
@20ft its very close to the i-10k,
Maybe if i raised them higher the GM would be in front a little.

I like your input Bob, and have to admit, I have wondered if the GM has too little energy in the higher angles (which you have in the bottom-fed 5/8 & NV4K) for as energetic local in-town contacts. How much are local contacts benefitting from a little 20°-35° energy, thus perhaps making the GM a little weak in comparison to even an A99 at times? Even for some non-skip DX, I wonder if sporadic E and even D-layer reflection isn't dependent on some higher angle radiation?

 

[gamegetter]

NB:
just my observations at my location and environment.

which is why i always say "you have to see what works best for you in your situation" via trial and error.

 

[Needle Bender]

jeez, 33 posts so far, and no one has questioned what an "equastion" is

NB:
just my observations at my location and environment.

which is why i always say "you have to see what works best for you in your situation" via trial and error.

How much have you tested different designs at your QTH? May I ask in what part of the World you reside?
Once the 5/8 P500 was up to 36' above ground a the radials, it's taking the ribbon against my new local stations running A99s, IMAXs, an 827 and MACO V5/8s. I asked, they are all at or above 36'. The guy with the 827 is also at 36' & right on my heels but has a bit more elevation (40') and 50% more power.

 

[Marconi]

I wonder what the Avanti design would look like with the shorter cone?

Good question NB. I tend to agree with Bob's ideas on the subject.

My free space model for the NV4k with 4 x 107" radials instead of S4's 3 x 90.5" radials...looks to improve the Sigma 4 design by producing a lower maximum angle and some improvement in gain.

I'm also working on the Vector models with different length radiators I posted above, in order to help show how they might respond being over Real Earth, with and without a mast, and using isolation (ISO) of the mast from the antenna.

 

[gamegetter]

NB
Looks like you need more power and an antenna that will "lock down the town"!