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

[Needle Bender]

I would really appreciate some Ideas, advice, anecdotal input, superstition, or whatever you're willing to share.

I picked up a Salute 7/8 the other day, (or at least what's left of one, missing the top 7' of which is a joke of 3/8" & 1/4" tubing that is evidently designed to land either on the neighbor's roof or in his pool), but have enough tubing in my arsenal to recreate it into a strong 7/8 or 3/4 wave survivor, I'm just not sure which will provide the best performance.

Maybe I'm whack but I believe the Vector type antenna is an off-center fed vertical full wave dipole which offers rephasing of the bottom 1/4 wave cone via it's inversion from downward to folded upward, thus capturing & neutralizing the inner out-of-phase bottom 1/4 wave current, plus radiating a small amount of the outer in-phase current, thus allowing a clean & efficiently fed, elevated 1/2 wave to perform at the best a full 1/2 wave can, plus a little more from the cone.

Now move to the 7/8. Same basic thing except an 1/8 wave added to the top of the 1/2 wave sticking out above the cone, thus making an elevated 5/8.

This seems a bit self-defeating, adding an of out-of-phase 1/8 wave to the bottom of a nicely designed & correctly phased 1/2 wave radiator. Seems it would cancel the next 1/8 wave up, leaving only the top 3/8 to do the radiating.

So I'm left wondering why it would ever have gone into production if it's a poor performer compared to it's shorter older brother? And what about that monster BigMac 7/8? I've read it was the Big Daddy of them all.

I dunno, at this point I guess I'm leaning toward the Vector 3/4, partly due to the fact that Sirio offer it thus, and I'd expect they'd instead offer the 7/8 version if it were superior, and partly due to my concern for screwing up a really cool 1/2 wave design. The guys at Avanti weren't slug-heads.

Oh no, I'm writing a bloody book
-But if there's a chance the monster 7/8 would reign supreme...

OK, I'll enjoy hearing from anyone who has a thought, or several, about which to commit to with this 'Parts antenna'.

Then there's the gamma match...

By the way, the full, uncut OEM cone on the Salute (Saluit?) is only ~91" from the bottom radial bolt to the top of the ring so I'd need to increase it to 104" if I were to correctly fab a Vector.
73
...

 

[222DBFL]

The sirio vector 4000 is listed as a 3/4 coaxial j pole. Here are the specs and length. Hope this helps.

 

[222DBFL]

I have this on the list as well as replacement for tornado. Any input is appreciated. I will only be able to get it to about 20-25ft at the base of antenna. How will it compare to a tornado at 27ft to feedpoint? And now rugged are the newest vector 4000's??

 

[222DBFL]

And thx NB for posting this question. Been one I've wanted to ask about, the antenna (vector 4000), anyway.

 

[bob85]

For me and my locals the extended version works a little better than the 3/4wave version with the original 90" cone but not the full so called 7/8wave of the original vector,
something close to shockwaves .82wave seems best, certainly better than any 5/8-.64wave i ever used on the same pole,

That could be due to the taller antenna seeing over obstructions rather than any magic from the extended monopole,
i find the extended 106-108" cone works a little better than the original 90" cone.

sirio claim the extended cone and shorter 3/4wave monopole give a lower radiation angle,

The BIG-MAC worked better than any other vertical on the same pole,
id put the tweaked vector somewhere between sigma4 and BIG-MAC,

one day i hope to build with some help from Henry a better version of the BIG-MAC co-linear idea.

IMHO by FAR the most informative article on that style antenna is Henry's article,
http://www.cb-antennas.com/

 

[gamegetter]

greetings needle bender:

there is much to be said about the design of said antenna, look back at all the threads and discussions that have occurred over the years. through all of this debate one thing is for sure: However and whatever you decide to do to optimize the design for your location, may not prove the optimum design for someone else at some other location....and vice versa.

 

[space cowboy]

go with 7/8 since you can cut it to 3/4 if you don't like it. harder to go from 3/4 to 7/8.

 

[Needle Bender]

For me and my locals the extended version works a little better than the 3/4wave version with the original 90" cone but not the full so called 7/8wave of the original vector,
something close to shockwaves .82wave seems best, certainly better than any 5/8-.64wave i ever used on the same pole,

That could be due to the taller antenna seeing over obstructions rather than any magic from the extended monopole,
i find the extended 106-108" cone works a little better than the original 90" cone.

sirio claim the extended cone and shorter 3/4wave monopole give a lower radiation angle,

The BIG-MAC worked better than any other vertical on the same pole,
id put the tweaked vector somewhere between sigma4 and BIG-MAC,

one day i hope to build with some help from Henry a better version of the BIG-MAC co-linear idea.

IMHO by FAR the most informative article on that style antenna is Henry's article,
http://www.cb-antennas.com/

Thanks guys, I appreciate the input.

Seems what you're saying, Bob85, is to have about the same thing as a Sirio 827 in radiator length above the cone. Curious if you've tried an 827 and if so, what results did you enjoy?

 

[bob85]

NB i have two 827's in the garage, They are the best 5/8 sirio make and the strongest / heaviest antenna sirio make,
The most popular 5/8 in this area,

Downsides are they use an open copper coil connected to what looks like sintered aluminum alloy hubs,
They are prone to going open circuit, which is why i was given two by locals who bought new ones rather than strip the old one down clean it up and put it back up,

The radials vibrate pretty bad if you bolt them to the house and don't use the anti vibration ring,
My 1-10k has the edge in performance on the same pole and its more reliable electrically.

 

[Needle Bender]

NB i have two 827's in the garage, They are the best 5/8 sirio make and the strongest / heaviest antenna sirio make,
The most popular 5/8 in this area,

Downsides are they use an open copper coil connected to what looks like sintered aluminum alloy hubs,
They are prone to going open circuit, which is why i was given two by locals who bought new ones rather than strip the old one down clean it up and put it back up,

The radials vibrate pretty bad if you bolt them to the house and don't use the anti vibration ring,
My 1-10k has the edge in performance on the same pole and its more reliable electrically.

Ah, you're addressing something I've wondered;
So the somewhat shorter, 'less-than-a-full-.625-radiator-827' doesn't keep up with the I-10K. -And so I would presume nor would one expect it would keep up with a Tornado, P500, Sigma-II 5/8, or other full 22.5'-ish radiators, etc., strictly speaking with regard to performance?

 

[bob85]

The 10k has an edge in my tests and the only other local that swapped from 827 to i-10k,
id put that down to lower loss in the matching and having full size radials,
The length of tornado 827 and i-10k radiators are so similar it wont make or break the performance,

The only tornado we tested was the old style with 4 short radials, it lasted a few days at most before the wind smashed it up so we never got a chance to do a direct comparison against the 827 on the same pole, it was replaced by an original sigma4 that outperformed it.

 

[Needle Bender]

...The only tornado we tested was the old style with 4 short radials, it lasted a few days at most before the wind smashed it up...

Got me laughing with that one

I really can't see any more than a negligible efficiency difference possible between the .625 matching networks in question, ie: I10K, Sigma2, P500, even the R/S .64 coil, other than perhaps power handling.
All they need to do is drop 150Ω-200Ω down to 52Ω, that shouldn't be noticeably lossy regardless of the design used, but I do prefer a DC ground shunted matching network.

Anyway, I've decided to support Sirio & just purchase a new Vector 4K

...then get out the hack saw and have a real good time with the Salute. I've got this wacky idea I want to try.

Pictures at 11

 

[222DBFL]

Someone on another forum posted one he beefed up, a vector 4000. NB when you get the antenna, could you post up how flimsly or what not it is. And how high you plan to go with it?? Just cirious. Want to put one of these up but the weight is my biggest factor as to how high I can go. Thx much for any replies.

 

[bob85]

There certainly are differences in how they perform in our tests NB,
What causes it is open to speculation, i look at whats notably different and that's the full size radials and the matching,

good luck with your new vector, i see no harm in experimenting to see what works best for you,
some people swear by the gainmaster but in my yard on a 20ft pole it plays second fiddle to my 10k by a small margin..

 

[Marconi]

I like my GM because it is streamlined, lightweight and easy to install, and is as good in performance as any other CB mono-pole vertical I have.

But the big thing IS it produces very little to no detectable inference at my location, and is very quiet in operations compared to some others I own.