Vector 4000 Remake

[HomerBB]

A while back I put together a Sigma IV hoImebrew. It seemed not to be as successful an antenna to me as the previous Qv4k homebrew. I figured I was done with this style antenna until an intriguing possibility in the mechanical structure of the antenna I had made led me to believe I might see a different result if I changed the Sigma IV in two basic ways.

1. turn it into a four tube basket like the Vector 4k instead of the three tube basket it has, and
2. Redo the basket/cone tubing mount bracket so that there was a little space between the vertical and the bottom of the radials.

In the previous antenna the radials ascend directly from against the vertical :

I will be adding the additional radial and using this bracket I made to create some stand-off at the lower end of the vertical:

Some modeling done for me by a good friend, Marconi, suggests there may be some advantage to having the antenna structured in this way. I hope to find out if possible.

Perhaps time will tell . . .

 

[HomerBB]

So that everyone is completely aware of the modifications that will be made to the antenna getting it where I want to go I will place some photos here to reference the before and after changes to.

The antenna vertical is currently 29' 8-1/2" long.
The 3 radials (sic) are each 93-1/2" long from bottom tip to the ring tip.

 

[The DB]

Uh oh, hes at it again. Always love watching these builds...


The DB

 

[HomerBB]

Need a fix

 

[HomerBB]

 

[HomerBB]

FYI:

I will be adding the additional radial and using this bracket I made to create some stand-off

at the lower end of the vertical:

Homer, how difficult and what went into making the bracket for your vertical? Im needing something very similar to this.

Jaybird,
Difficulty is an individual matter, but this is not difficult to me. If I were to rate it I'd say medium difficulty for most

folks. For you, it's likely a breeze if you want it done. The joy is in the doing and the result.
I cut some aluminum bar strap into shorter pieces. I then laid them one at a time across a 1" gap on the bench vise. I took

the large end of my 1/2" brake-over bar from my socket set, laid it across the center of the aluminum stock along the gap in

the vise, then struck the handle with a hammer. This caused the aluminum flat bar to curve upward. When I had enough curve

to match the the roundness of a tube I then put the flat bat in the vise to the point I wanted to bend the then bar

backward. I did this on each end until the bar ends were equally bent back to form a 90 degree angle between them.
After I was done drilling the holes with a bench press, I smoothed the edges with my belt sander.

 

[HomerBB]

Some of you reading may be able to help me with this. Where do I need to go with each of these two things to optimize this antenna.

Vertical length
radials length

I ad a computer crash, and have misplaced my written notes on this.

These are what is on the Sigma:


The antenna vertical is currently 29' 8-1/2" long.
The 3 radials (sic) are each 93-1/2" long from bottom tip to the ring tip.

Thanks

 

[2RT307]

Glad to see the cooler weather has you shifted back into project mode, Home. I always enjoy following these builds.

73,
RT307

 

[bob85]

homer,
i think the monopole length depends on proximity to ground and surroundings detuning the antenna to some extent, i ended up a little longer than you or shockwave but mine was close to the ground,

i only tested radials from a little over the factory 90" and shorter,
going shorter was the wrong choice for my install,
the new vector uses longer radials about 106" i have the longer tubes but lack the enthusiasm,
my heads full of single ended directly heated triodes and electrostatic speakers right now,

your gamma strap looks longer in the pictures than any of the factory antennas,

your 4 radial hub looks like mine but i used 4 original avanti hub pieces bent to fit a tube a little under 2" diameter.

Some of you reading may be able to help me with this. Where do I need to go with each of these two things to optimize this antenna.

Vertical length
radials length

I ad a computer crash, and have misplaced my written notes on this.

These are what is on the Sigma:


The antenna vertical is currently 29' 8-1/2" long.
The 3 radials (sic) are each 93-1/2" long from bottom tip to the ring tip.

Thanks

 

[HomerBB]

Glad to see the cooler weather has you shifted back into project mode, Home. I always enjoy following these builds.

73,
RT307

I've been antsy, Brett. It will be a short window before the winter closes end. Gotta get back to work . . .

 

[HomerBB]

homer,
i think the monopole length depends on proximity to ground and surroundings detuning the antenna to some extent, i ended up a little longer than you or shockwave but mine was close to the ground,

i only tested radials from a little over the factory 90" and shorter,
going shorter was the wrong choice for my install,
the new vector uses longer radials about 106" i have the longer tubes but lack the enthusiasm,
my heads full of single ended directly heated triodes and electrostatic speakers right now,

your gamma strap looks longer in the pictures than any of the factory antennas,

your 4 radial hub looks like mine but i used 4 original avanti hub pieces bent to fit a tube a little under 2" diameter.

Thanks, Bob.
This will be very helpful. I wanted to know I was in the ball park.

The Gamma strap i never had a length for, I don't think, so I assumed the gamma needed to stay on the same plane as the radials.

How long would you suggest?

 

[HomerBB]

 

[HomerBB]

Today I have completed assembly and put it up at 27.5' to the coax connector. Tomorrow I'll try to tune it up with the MFJ-259b. I have run out of time today. Just leaving the Gamma where it was before, making the changes I have, and bringing the Gamma itself inside the cone of the radials it sits at 1.35:1 on 27.385 according to the SWR meter at the shack. I can talk and receive, but I won't be confident of the tune until I can use the analyzer: hopefully tomorrow.
I have set it at 27.5 feet although nearly another 10' of height is available to me. Coincidentally, the bottom of the vertical dipole sits about 45
feet away at that elevation so i thought I may as well see if there was any thing gained using the Q2v4k - :icon_e_wink: - that I can detect. I will raise it on up later. I know, I know, there are many who will want to have a hemorrhage over two masts, two coaxes, and a switch, but I am NOT going to put the two of them up and down on the same mast because of the antenna free-bleeders. See a doctor.

No, the antennas aren't leaning. The camera is weird . . .

 

[bob85]

i don't remember the exact length homer, i think i have one in the shack i will measure if i can find it.

two antennas and a switch :laugh:

 

[HomerBB]

Thank you, Bob. My fingers are crossed.