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Post by homerbb on Sept 14, 2012 14:53:29 GMT -5
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 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 . . . |
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Post by homerbb on Sept 14, 2012 16:49:00 GMT -5
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.      |
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Post by Marc on Sept 14, 2012 17:57:06 GMT -5
Homer
The new setup looks more like the org avanti setup just might do the trick!!?
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Post by homerbb on Sept 14, 2012 20:15:23 GMT -5
Well, I hope to get the antenna to behave more as it should. I may have to buy some better radials material, too. I want it to work at least as well as the first V4k i made. This Sigma just wasn't quite there.   |
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Post by homerbb on Sept 15, 2012 11:57:01 GMT -5
FYI: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. 
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Post by homerbb on Sept 16, 2012 22:28:53 GMT -5
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Post by zman on Sept 17, 2012 18:31:09 GMT -5
Makes me want to revisit my Avanti Sigma 4 and dig it out of the scrub brush along the fence!!!!
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Post by homerbb on Sept 17, 2012 18:50:47 GMT -5
If you don't have the time, send it my way! 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 -  - 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.  ;D      No, the antennas aren't leaning. The camera is weird . . . |
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Sandbagger
Administrator/The Boss 
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Post by Sandbagger on Sept 18, 2012 6:17:33 GMT -5
Makes me want to revisit my Avanti Sigma 4 and dig it out of the scrub brush along the fence!!!! I used to use a Sigma 4 back in the 80's and 90's at my old location. Compared to other omnis I've owned and mounted to the same mast, the S4 was the best performing out of any of them. Stronger signals to the locals and better receive. And this was compared to a 1/2 wave GP, an Astro Plane, and a 5/8th wave GP. Of course the Astro Beam mounted on the tower would best the S4, but that's to be expected. |
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Post by homerbb on Sept 18, 2012 18:55:42 GMT -5
I did a little more modification to the antenna today, but it isn't so apparent as to show much. I put in a different Gamma sleeve, and set to trying to tune the thing up using the MFJ-259b. What a challenge. The work platform of the tower was pretty useless with this antenna because although I could reach the coax connector to hook up the analyzer, the gamma adjustments were completely out of reach. SO the tower was cranked up and down several times until I ran out of tie and just quit. Too tired for more today. I am not sure where to take it from here, but it isn't where I hoped it would be in terms of the analyzer tuning. I have no references as to what to expect from tuning this type antenna using one. I have been unable to locate anything online referencing the anticipated outcome. As for reading SWR with the SWR meter in the shack - it loves this antenna. For now, some analyzer readings: with 89" coax into the shack - 28.665 ------------- 2.0:1 ----- R=55 ----- X=27 27.895 ------------- 1.5:1 ----- R=86 ----- X=0 27.385 ------------- 1.3:1 ----- R=46 ----- X=14 26.585 ------------- 1.5:1 ----- R=58 ----- X=20 25.725 ------------- 2.0:1 ----- R=82 ----- X=24 with 1/2ƛ electrical jumper on tower - 28.475 ------------ 2.0:1 ----- R=38 ----- X=13 27.550 ------------ 1.3:1 ----- R=48 ----- X=12 27.385 ------------ 1.3:1 ----- R=46 ----- X=15 27.345 ------------ 1.3:1 ----- R=48 ----- X=16 26.965 ------------ 1.5:1 ----- R=69 ----- X=18 26.480 ------------ 2.0:1 ----- R=118 --- X=0    |
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Post by homerbb on Sept 19, 2012 20:42:49 GMT -5
I added the capability of adjusting the length of the radials. I now have them a standard New V4k 106'5". I did not have the time this evening to remake the gamma tapping strap . . . tomorrow. I can say that there is a very noticeable difference in the receive on the Q2V4k and the dipole even as it is. Today I had only the time to fasten the ring to the radial mounts with self-drilling screws. Tomorrow I will replace them with some stainless steel screws and nuts.   |
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Post by homerbb on Sept 20, 2012 16:12:53 GMT -5
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Sandbagger
Administrator/The Boss
Posts: 6,247
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Post by Sandbagger on Sept 20, 2012 18:34:01 GMT -5
Okay. I got the dimensions adjusted to specs, and then I made a new Gamma Match. I felt the old one wasn't handling this antenna properly, so I made a bigger/beefier one. The new Gamma is a virtual copy of the old dimensions, with exceptions as noted below: tube -------- 5/8" diameter x 17" long (as opposed to 1/2" x 17") rod --------- 1/2" diameter x 30" long (as opposed to 3/8" x 33") I also made a new dog bone/strap from 1/8" x 3/4" aluminum flat bar with the tube to rod centers length @ 6" (as opposed to 5.25"). The Gamma Rod length is pulled out from the tip of the rod back to the sleeve tube top 23". The Dog Bone is set from the bottom radials bracket up the Vertical Radiator to a distance of 33". I put the MFJ-259b on the antenna with the E1/2ƛ jumper and measured for with the antenna tower standing in the air and feed point at 27.5" height these results:I then went into the shack with the coax feedline back on the antenna and with the analyzer measured the results from there:"Feelin' so much betta"Adding a feeline will almost always affect the readings you get from SWR meters and even a more sophisticated tool like the MFJ. It's tough to predict what the effect will be, but the more reactive the antenna is the more of an effect it will likely have. And of course, the length of the feedline will change the effect as well. |
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Post by homerbb on Sept 20, 2012 20:11:23 GMT -5
You're right. I am just happy that the antenna tuned, and that it isn't so incredibly widebanded as to indicate inefficiency.
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Post by homerbb on Sept 21, 2012 22:25:20 GMT -5
Latest photos. I moved the X strap that supports the radials in position upward . It wasn't long enough to go any higher until I modified it.   |
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Post by homerbb on Sept 22, 2012 10:22:23 GMT -5
I have made a few comparisons of this one, the Q2v4k, to the dipole with both having a bottom height of 27.5'; the Q2v4k (Quasi 2 Vector 4000 Homebrew) has handily beaten out the humble, but nimble, dipole in every case except those within 2 miles of me.
I am seeing and hearing perceptible differences between them, and reports are confirming this for me by some with whom I am in contact.
In the DX melee it is difficult to get reports, but I have managed some on the upper quieter channels with the Q2v4k reigning chief over the dipole by at least 1 to 2 S units. We know DX is the great equalizer.
On the local scene when DX is not ruling the band I have enjoyed better results with the Q2v4k as well.
Rogers, AR to Jane, MO ---- 20 miles as if in the neighborhood.
Rogers, AR to Berryville, AR ---- 31 miles, giving him 7 - 9 with him sounding as if he were within the 20 mile range.
Rogers, AR to Wyandotte, OK ---- 47 miles through the Ozarks with clearly readable transmissions each way. He sounded as if he were half that distance. He disappeared when I switched to the dipole.
I can not prove this, but I sincerely believe this antenna does as it is purported to do, it lays the signal much nearer the horizon than other omnis.
In every case I was working with 150 watts PEP.
I an hoping to catch some of those stations that work AM out in the Branson , MO area A 68 mile trip though some of our most rugged terrain, and beyond that that I have not heard since the Qv4k(my original homebrew) went on to another home.
This one has required more patience as I have striven to make it a permanent build since the beginning. It is not a soft line and sash cord build, no duct tape either!
Listen up for me, I'll be hunting you.
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Post by homerbb on Sept 23, 2012 19:06:21 GMT -5
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Post by homerbb on Oct 14, 2012 18:20:38 GMT -5
A question that always arises is about the durability of the Vector 4000. A lingering complaint is that this antenna lacks integrity and will break easily. For this redo I wanted to add more structural strength to the original design. I double walled the lower 5.5'. I used heavier walled tubing for the cone radials, I beefed up the dog bone for the Gamma Match, and rebuilt the cross supports stronger, but even a third modification for that has not yet been added to the antenna. It is to go up a little higher on the vertical when I out it on (this week). However, we had a monstrous storm pass through Saturday night. Winds were in excess of 60 MPH. Straight line winds were around 40 MPH continuously. I crossed my fingers and hoped for the best. I went into the shack and checked the SWR several times as the Moxon and the Vector 4000 wiggled and swayed with the winds. The Moxon mostly warped a bit here and there, but the Vector 4k laid over nearly horizontal. The V4k held a steady 1.0:1 SWR, and the Moxon moved from its usual 1.15:1 SWR on 27.385 to 1.4:1 settling back to 1.15:1 when it was all said and done. I took a quick photo of the two of them this morning after the storm. Neither antenna suffered any damage, but the very top of my push up pole beneath the V4k was left with a permanent bend which has my antenna leaning quite a bit. I am pleased for the way both antennas behaved in that storm. Trees fell, some buildings were roof damaged, and some smaller structured were demolished by the strong winds. Some trees lost limbs of 6" diameter. One of my neighbors saw is 8" trunk on a Maple split down the middle.  |
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Post by homerbb on Oct 14, 2012 19:35:24 GMT -5
As it turns out we did have a tornado. This one set down 2 miles from my house. ROGERS, Ark. (AP) - The National Weather Service has confirmed a tornado touched down in Rogers during overnight storms. A survey team from the National Weather Service in Tulsa, Okla., surveyed the scene on Sunday. A number of businesses sustained damage, including in the Pinnacle Hills commercial area. The weather service says radar indicated the twister touched down just after 9:30 p.m. Saturday as a wave of heavy rain and high winds buffeted the area. No serious injuries were reported. The storm knocked down trees and power lines. The weather service initially rated the tornado as an EF-1, meaning it would have had winds of between 86 mph and 110 mph, but forecasters later said the tornado had not yet been rated.[/i]   |
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Post by cbrown on Oct 15, 2012 8:43:38 GMT -5
That was a pretty good wind test, then. Hope non one was seriously hurt!
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Post by homerbb on Oct 15, 2012 9:41:23 GMT -5
No injuries reported.
The thing is, watching the wind in the trees and such, my impression was that they were greater than what I first read, 60+ MPH. Now it appears they likely were!
I'm just glad the twister stayed a couple miles away!
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Post by cbrown on Oct 16, 2012 8:31:25 GMT -5
With a tornado nearby, I imagine they were a lot higher than 60 mph.
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Post by homerbb on Oct 16, 2012 23:22:21 GMT -5
My thoughts, too.
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Post by trashyd201 on Feb 8, 2021 22:16:38 GMT -5
You're right. I am just happy that the antenna tuned, and that it isn't so incredibly widebanded as to indicate inefficiency. Beautiful Build of the V4K These are Amazing antennas. I had 3 of the earliest versions of this design two were called a Galaxy27 & the 3rd was a Salute LW150. I just bought the New Vector 4000 will see how this one compares to their performance. |
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- 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. 
;D 
