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

[Needle Bender]

Pointless exercise. It'll make no difference.

I agree, and notice I mentioned .7 to allay any confusion between 26.8 & 28.6 but that was PRIOR to my realizing that 'Primary' WAS 28.6".
I'd like to know Bob85's final dimensions of both radiator and cone. I like 28.7' because of the fuller 30 degree pattern sufferring minimal loss at 8 degrees.

 

[Needle Bender]

I posted three Vector models. I also posted a Sigma 4 model to specs. All with masts attached.

1. 28.6' model is the Vector extended as your suggested, The black line is the Primary model
2. 26.8' the stock Vector and is blue

I should not have added the last two models. Forget the comparisons I added with the S4 length idea for the last two, green and red patterns. Black and blue are the two colored line patterns that apply to your question...as I understand it.



Sigma 4 model is 331" x .75" inches used for the overall radiator length, and 90.5" x .50" inches used for the overall length of the three radials.



NB, I will add the 1" to the "Vector 28.6' with mast" model that is set at 28.6' inches already...the black line in the overlay patterns above. Do you really think one inch will make a difference that matters? I would be surprised if it did. The Vector model also has a 5" inch diameter top hat that is not included in the overall radiator length, but is part of the model.

Hey Marconi, did you also shrink the ring down to 24" diameter on the Sigma4, as per the Avanti manual on CB T

 

[Marconi]

Hey Marconi, did you also shrink the ring down to 24" diameter on the Sigma4, as per the Avanti manual on CB T

NB, I don't think the Avanti version has a 24" hoop diameter on their Sigma 4. It shows to have 4 x 24" x 3/8" sections that make up the hoop however, but I'm not real sure what the exact hoop diameter really is on this model.

My S4 is made by Antenna Specialists and shows the hoop to be very close to a 30" diameter, and I think the original Avanti is close to 30" also.

 

[Needle Bender]

NB, I don't think the Avanti version has a 24" hoop diameter on their Sigma 4. It shows to have 4 x 24" x 3/8" sections that make up the hoop however, but I'm not real sure what the exact hoop diameter really is on this model.

My S4 is made by Antenna Specialists and shows the hoop to be very close to a 30" diameter, and I think the original Avanti is close to 30" also.

Oh geez, another 'oops'. I thought I hit cancel, after I double checked and saw it was the sections not the diameter. Was surprised when I got email letting me know you'd replied - just not my day, I guess

 

[Marconi]

Not to worry NB, wait until you get my age 77 yesterday.

 

[Needle Bender]

Not to worry NB, wait until you get my age 77 yesterday.

Well Happy Belated Marconi! I can't say you're maturity is showing, sharp as a tack from my perspective, and I enjoy your expertise with the patterns which I've found very helpful.
I was thinking earlier today, might be enlightening to overlay an Imax, Penetrator, Vector4K & a .64 - all mast mounted at both 36' & 50' over real ground

 

[Marconi]

I was thinking earlier today, might be enlightening to overlay an Imax, Penetrator, Vector4K & a .64 - all mast mounted at both 36' & 50' over real ground

NB, I have not put much work into my models for the Perpetrator 500 or a .64 wave antennas. The only .64 wave I know that is advertised as a .64 wave...is the Wolf .64. As constructed...my two models for the SP500 and the Wolf .64 show to be super sensitive (reactive) to minor changes I might make...and IMO this is a possible sign of a questionable model. I'm not sure how reliable they are as models, so I won't post them here as the comparisons you suggested.

I can make an Imax and setup the overall length a bit longer than a .625 wave to simulate a .64 wave radiator. I may do this Imax .64 wavelength along with an Imax at .625 wavelength, and compare the pattern overlays along with my New Vector 4K model, like you suggest...at 36' feet and at 50' feet.

 

[Needle Bender]

NB, I have not put much work into my models for the Perpetrator 500 or a .64 wave antennas. The only .64 wave I know that is advertised as a .64 wave...is the Wolf .64. As constructed...my two models for the SP500 and the Wolf .64 show to be super sensitive (reactive) to minor changes I might make...and IMO this is a possible sign of a questionable model. I'm not sure how reliable they are as models, so I won't post them here as the comparisons you suggested.

I can make an Imax and setup the overall length a bit longer than a .625 wave to simulate a .64 wave radiator. I may do this Imax .64 wavelength along with an Imax at .625 wavelength, and compare the pattern overlays along with my New Vector 4K model, like you suggest...at 36' feet and at 50' feet.

oh Marconi, I was just thinking a 22.5' with 1/4 wave horizontal radials for the .625 and 23' with the same radials for the .64 and whatever matching system you like to get 50-52Ω

 

[Marconi]

oh Marconi. I was just thinking a 22.5' with 1/4 wave horizontal radials for the .625 and 23' with the same radials for the .64 and whatever matching system you like to get 50-52Ω

NB, I haven't figured out how to use the matching feature that comes with Eznec, but IMO and within reason, I don't think correcting the SWR to show a better match makes much difference in the performance of a model, at least not so one can easily tell just using our radio.

Furthermore, I see virtually nobody using matching with their models in support of their antenna comments in professional type antenna literature, including W8JI and Cebik. This all may say something about why we don't hear much discussion on matching issues talked-about in the antenna modeling literature also.

I have made an I-10K model where I physically added the trombone matching device, and it does show to positively effect the pattern and and improves the match at the feed point. The addition of the trombone matching device also shows to add some horizontal radiation to the pattern. So, if this model is close to correct...then this big I-10K trombone tuner may be what accounts for the improved performance many CB operators report over other 5/8 wave type 11 meter antennas. IMO, the addition of a physical matching device to some of the other models of CB antennas...might also make some difference similar to what is noted for this model.

I posted this model on WWDX a while back, but it produced little interest.

This said, I tend to agree with DB when he says adding the matching feature to our models is beneficial to improved accuracy in modeling.

DB, can match his models using 4Nec2. If matching is essential for this idea why don't you ask him if he will do this project for you?

 

[Marconi]

NB, below are my two overlays of the New Vector 4k, a .64 and .625 wave radiators at 36' feet and at 50' feet in height above average Earth.

These models do not include matching. The Vector models at both heights show SWR near 1.50:1 at both heights so it looks as the antenna does not need much transformation in order to match. The other two models show <>35.0:1 SWR and need matching.

We see here that there is not much difference in performance, except it looks like the Vector does better higher up than the other two. I did not include the Imax with 62" radials, but it is worth noting at 36' feet it shows more gain, by .36 dbi, than all the others at 36' feet.

In my real world experience with these types of antennas my antenna signal reports tend to support these similarities in results...I just don't see the signal difference that others report, and thus I don't see the gain differences either.

If I didn't see this using my modeling...I would have only my words and my signal reports I've posted to support my claims.

 

[M0GVZ]

In my real world experience with these types of antennas my antenna signal reports tend to support these similarities in results...I just don't see the signal difference that others report, and thus I don't see the gain differences either.

Part of it is down to faults in testing methodology from a lot of people and part of it is them trying to convince themselves that they've not just blown $250 on an antenna which works no better than the $50 one it just replaced. A lot of the wording in the posts in this thread and others in "is X better than Y" and "if I do this how much better will that make it work?" pretty much give the impression the poster is trying to convince themselves they've not just wasted a bunch of money.

Like you I've done a lot of antenna modelling and I've built a lot of what I've modelled. The real world results I've seen from the various designs and alterations to those designs have convinced me that the models are sufficiently accurate enough that we can take the comparisons of various CB models like you've done and that the differences illustrated between those being compared are going to reflect the real world. Any large differences are therefore down to the fact there's been a change, either a previous unrecognised fault has been rectified, some condition has changed such as using a different length pole and thus changing the height of the antenna which improves or worsens local contacts or in the case of DX that the ionospheric conditions have changed.

Some of the gains claimed are just quite ludicrous. 6dB is a fourfold increase in signal and 6dB difference is damned hard to the point I'll say it is impossible to achieve from one antenna to a similar antenna - i.e an Imax 2000 to a Vector 4000. Some claim several S points but that's just ridiculous. Here's what an increase of 6dB looks like and its certainly not several S points and to get that 6dB increase I had to double the size of the antenna. I certainly didn't increase it by just a few percent as is the difference between a 5/8 wave and .64 wave.

 

[Needle Bender]

Thanks Eddie & Conor. I appreciate all input & info. Too bad Donald tucked tail & ran away, I'd enjoy hearing his input regarding the Vector patterns. I wonder if he'd argue they're inaccurate due to the program inability to correctly deal with it's curent nodes?

While motoring around Lake Tahoe a few weeks ago I heard a number of stations from the valley but only the two ice cream cone antenna stations hit S7 & S8 where the similar power guys on 5/8 antennas were only S3-S5, this from approx 85 miles away in my mobile. I had Shock's posts vehemently claiming, the Vector performance is much superior to that of a 5/8, ringing in my mind

 

[gamegetter]

too many variables...

were all stations running same power and were at the same distance to you
did all antennas have the same line of sight with out any obstructions, or were there more trees, buildings or elevations affecting some stations and not others.
how do we know that each individual station was running as efficient as it could on so many potential different equipment, wiring, and other variables.

if you were mobile, then moving around could introduce several of the above variables.

 

[Needle Bender]

too many variables...

were all stations running same power and were at the same distance to you
did all antennas have the same line of sight with out any obstructions, or were there more trees, buildings or elevations affecting some stations and not others.
how do we know that each individual station was running as efficient as it could on so many potential different equipment, wiring, and other variables.

if you were mobile, then moving around could introduce several of the above variables.

Oh, I drove maybe 12-15 miles while listening and the two stations with Vector 4K type were consistently stronger than the similarly powered stations using mostly 5/8 including a couple with an 827 and one Shockwave 5/8, and all typically run 2 transistor amps, except the guy with the Shockwave 5/8 who runs 4 transistors. I doubt it would be remotely plausable to blame a tree or building as the reason for the Vector clones to be consistently stronger, but again, it was just an anecdotal observation.

 

[222DBFL]

Just ordered myself a NV4K yesterday. Gonna give one a shot here!! I think if I get the feedpoint to about 30ft. I'll be okay. That will place tip at 57ft. Give or take. Should be high enough to get my signal out a bit. Any wise words from you gents as to any mods needed? Is the cutting slits and hose clamp mod worth the effort? If so I'll be doing this before placing new antenna up. It is almost 4ft shorter than the original 31ft. 8480mm vs 9540mm or so the older was. 8480mm= 27.82ft. Vs. The 9540mm which equals about 31.29ft. So antenna should be a bit stiffer. I'll have to look it over when I get it. Again, any advice as to mounting and mods to strengthen antenna are all appreciated. It's not going in a high wind area per say, although we get our share of bad weather, my antenna will have some trees that help block a lot of wind. So I al hoping this will not be an issue. I've also read to guy off the top sections with a couple runs of Dacron rope. Idk, so I am asking. Thx for any responses and look forward to getting a vertical back up soon!! The A99 (dummy load) wasn't cutting it!!! And it was bought as a gift and I got to choose which one I wanted so I hope I chose correctly.