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Modified Vector 4000

Discussion in 'CB Antennas' started by bob85, Oct 3, 2009.

  1. BJ radionut

    BJ radionut Supporting Member and 6m addict

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    Vortex Antenna.jpg


     

  2. Marconi

    Marconi Usually if I can hear em' I can talk to em'.

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    Bob, I may have some details mixed-up here, but on 12/31/20 your post #691, discussing a V4K with 4 x 1/4 wave horizontal radials added below the feed point, and measuring the signals, at close range, using your dbm device...showed 89.2 dbm with radials...and 90.2 dbm without the horizontal radials added below the feed point. You reported this produced a net difference 0.5 Sunit :unsure: in signal loss for the V4K without the radials vs the V4K with the radials added showing a better signal.

    Considerations Continued:
    Then on 1/7/21 you did a similar comparison in your post #728, for the V4K with the cone using 1/4 wave radials (stock type V4K) and it produced 89.7 dbm vs. a model with 3/8 wave radials instead, like the Vortex Q82 Mark 2. And, it showed 86.1 dbm for a net difference of 3.6 Suints...I think.:unsure:

    Did I get close in my considering your results here. If not, could you fill me in on this difference, which seems like a lot more advantage for the Vortex Q82 M2 over the stock V4K similar to what Vortex is claiming?

    I know the Vortex website use to show us a big gain which was way more than my models showed. I claimed that their model must have been showing overstated gain...which I see a lot in my models as I attempt to get the models more correct.

    The definition of Vortex is a whirling mass. IMO this whirling mass could be going up into the sky above Earth or along the horizon, or it could also mean going down a rabbit hole. Forgive my attempt at a little humor.

    I seem to recall that maybe DB warned me that the Average Gain results can be misleading, so for several day I've been trying to model this distinction or idea as noted. I could have got what DB said wrong also...I have not tried to find this post were we were talking about AG results and accuracy.

    DB, do you remember anything along these lines with me and this issue?


     
    #737 Marconi, Jan 8, 2021
    Last edited: Jan 8, 2021
  3. The DB

    The DB Sr. Member

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    The only thing I can think of is I did mention that if AGT was far enough off that I have noticed that the correction factor didn't line up with the results after correcting the AGT in said model. This was far outside the range of what we would call acceptable AGT, so I doubt it is anything you have to worry about.


    The DB
     
  4. Marconi

    Marconi Usually if I can hear em' I can talk to em'.

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    I don't think that was what I had in mind, but thanks for the response. If I see an Average Gain that is as bad as you described, I'd figure there is something grossly wrong with the dimensions of said wire or a wire is loose somewhere in the model.

    Like I was changing the feed point around to get a better match and I accidentally change said wire number instead...for example. :LOL:
     
    #739 Marconi, Jan 8, 2021
    Last edited: Jan 8, 2021
  5. bob85

    bob85 Supporting Member

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    Eddie, the first test with & without radials was 89.7dBm without radials 90.2 with radials,

    The 3/8 cone version did show 3.6dBm higher signal ( not gain ) & 3dB+ improvement in SNR,
    that's significantly more than Vortex claim for the increase in low angle gain,

    since the tests were not done at the same time & only 1/4wave @50mhz above ground
    i put no stock in the 3.6dBm advantage but its made me interested enough to build another with 1/4wave radials to do more testing,

    Both me and Nav think there was likely an issue with the first test antenna,
    i hope there was a fault, i don't want the 3/8 cone to perform better,

    3/8 radials on 27mhz are a floppy pita even using the stupid duty Vortex tube,

    i sorted more old vector parts today, they need a good clean & tubes slotting for hose clamps,
    hub needs drilling & tapping, grub screw is siezed & smaller than later versions, hoop & gamma need cutting down.
     
  6. nav2010

    nav2010 Active Member

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    Why would you want the 1/4 wave basket version to perform better?
    An 1/8th wave extra on the basket ain't gonna cause any stability issues weather wise and you may have dropped on a unique design upon which you can further elaborate and experiment. You won't find that out until we do a one for one test in a 15 minute window.
    The 6m version of the V4000 with 1/4 wave basket may not perform as good as the 27mhz version does because of the difference in frequency and proximity to ground but the 3/8th version may perform equally well as the 27mhz version responding differently to ground effects.
    The real crunch test is both antennas at least one wavelength above ground on the same mast.
     
  7. bob85

    bob85 Supporting Member

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    Looks weight & wind load is why i like the 1/4wave version,

    3/8 radials on 50mhz are reasonably stiff with 1 spreader & the shorter monopole is stiff,

    Vortex use the strongest tube ever seen in a cb antenna & the 13ft+ radials still flop around unless you use 2 spreaders, it weights 17kg & its top heavy with high wind load high up on the antenna,

    no other cb vertical puts as much load on your mast as the q82 mk2.
     
  8. Marconi

    Marconi Usually if I can hear em' I can talk to em'.

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    I know Bob, you told us these tests were close up and preliminary. I just wanted to make sure I was not thinking one way and you the other.

    At 5 or 6 miles I've seen some strange results while comparing some of my antennas.
     
  9. freecell

    freecell Member

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    • "the first test with & without radials was 89.7dBm without radials 90.2 with radials,"

    dBm = dB-milliwatts
    mW = milliWatt

    • Power (dBm) Power (dBW) Power (watt) Power (mW)
    • ...-100 dBm .......-130 dBW ......0.1 pW ......0.0000000001 mW
    • ...-90 dBm .........-120 dBW ........1 pW ........0.000000001 mW
    • ...-80 dBm .........-110 dBW .......10 pW .......0.00000001 mW
    pW = picoWatt

    0.1 pW = 1 ten billionth of a watt
    1.0 pW = 1 billionth of a watt
    10 pW = 1 hundred millionth of a watt

    without the - operator in front of the figure everything changes.

    89.7 dBm = 933,254.300797 Watts
    90.2 dBm = 1,047,128.548051 Watts

    0 dBm = 1 mW or .001 Watts

    ?
     
    #744 freecell, Jan 9, 2021
    Last edited: Jan 9, 2021
  10. bob85

    bob85 Supporting Member

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    -89.7dBm below 1mw, its a vector 4000 not Wardenclyffe tower;)
     
    freecell likes this.
  11. freecell

    freecell Member

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    nikola never worried about a few pW.
     
    bob85 likes this.
  12. Shockwave

    Shockwave Sr. Member

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    How does going beyond 1/4 wavelength radials in the basket, impact the feedpoint impedance that the CMC would be loaded with? Doesn't the low impedance path that the CMC is loaded with at 1/4 wavelength, start to rise exponentially, towards about 2,000 ohms once you reach 1/2 wavelength? What prevents this mismatch from causing a loss in performance, as a result of minimizing the CMC loading, by raising its path of resistance?

    What happens to the phase relationship between the basket and the main radiator when the basket covers more than the first 1/4 wave of out of phase radiation, from that main radiator? Don't we begin to cover over a portion of the in phase radiation from the center pole, or is that main radiator extended in proportion with the basket length to prevent this? I may have missed it someplace but do we have models showing this phase relationship between these longer baskets and the central monopole?

    I can't help believe that on a band where most antennas do not completely clear the average tree line, that some of the improvements seen are not the direct result of simple added height. Marconi has been suggesting this for many years. I've also noticed that the advantage of adding another 1/4 wavelength or 10 feet in antenna height, mostly evaporates once you're already at 100 feet or more. On the other hand, if the center of radiation is not already clearing most roof lines or tree tops, another several feet could easily make a notable difference.

    nav2010 questioned the performance of the antenna when scaled to higher frequencies. I've scaled them down in physical size for some overseas clients to work on the VHF band III, at up to 200 MHz. with no reduction in measured gain. That is about the highest frequency I've found the design to be useful at because it has a unique "Achilles heel".

    In every other transmitting antenna I've worked with, once you work out every weak link in the design, the only thing you have to worry about is reaching a power level that will cause the antenna to arc from its end or tip. An easy fix on an end fed vertical with the addition of one Corona ball.

    The first CST computer model of this design showed an interesting phase relationship between the top of the basket ring and the central monopole inside. The phase difference is 180 degrees at the exact point that that we have a voltage peak along the radiators. This phase relationship causes an already high voltage point on the antenna, to be twice as much when measured between the ring an monopole.

    Now think about what happens when you scale the antenna to operate at twice the frequency... The gap between the top of the basket ring and the monopole inside, is cut in half. You quickly run into a situation at higher frequencies, where you're struggling to get the antenna to handle a few hundred watts, before it starts to arc here. That's why similar designs used beyond VHF high band, only handle a few hundred watts. You can't get around that problem unless the antenna is inside a vacuum.

    Even if you never run enough power to cause a Corona arc, adverse weather conditions will inhibit normal operation when the ring must be spaced too close to the monopole, due to frequency of operation. Because the top of the ring and the same location on the monopole inside, are high impedance points being 1/4 wavelength away from the source, they are also very easily loaded by things like snow and ice buildup between the two points. Once you're past 200 MHz. snow can wreck your VSWR.

    When the space between the ring and the cone is close enough that snow can fill the basket more than about 2/3rds of the way, or it directly bridges the gap between the ring and monopole, expect VSWR issues. If you happen to have this problem, you can fix it with a few feet of that outdoor, electrically heated plumbing tape. Because there is no insulator at the base of this antenna, you can wrap the area below the connector, where the mounting U-bolts are, with this tape. It will conduct heat through the aluminum to prevent snow and ice buildup in that critical area.
     
    #747 Shockwave, Jan 10, 2021
    Last edited: Jan 10, 2021
    HomerBB likes this.
  13. bob85

    bob85 Supporting Member

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    Donald,
    I take what Vortex claim with a pinch of salt until my tests show there is some truth in what they claim,
    You know where they got all the advertising claims for the original q82 from,

    The mk2 Vortex has a 3/4wave monopole with 3/8 cone,
    they don't extend the monopole when they extend the cone, in fact the monopole is a little shorter than the mk1 version with 1/4wave cone,

    I don't know what to expect when i compare 1/4wave cone to 3/8 cone as close to the same time as possible,

    what's happened so far is my scaled q82 mk2 had a significant advantage over the 1/4wave cone version,

    That's not what i was expecting & may not be the case when i have two antennas i can swap on same mast/coax within a very short time,

    i have never seen anything like that advantage when comparing other antennas & especially against what for me has always been the best performing vertical cb antenna,

    the results need a rerun in a more timely fashion,
    if any advantage is there when i have two antennas a rethink of what's going on is in order,

    i have not seen current distribution on the 3/8 version, the images on Vortex website are tiny thumbnails i can't see,

    did Vortex make a 3/4wave center fed dipole ?
    i aim to find out if they found something we all missed.

    putting the spreaders up at the hoop at a voltage node is not where i would put it even on 27mhz other than for a test for the reasons you outline above, it also looks Fugly,

    with 27mhz versions you don't really have an option they are so floppy.
     
  14. Marconi

    Marconi Usually if I can hear em' I can talk to em'.

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  15. freecell

    freecell Member

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    "The mk2 Vortex has a 3/4wave monopole with 3/8 cone."

    then how is it a .82λ vertical monopole?
    @ 26.800 mhz. it should be 30 feet in overall
    vertical length. 983.6 / 26.800 X .82λ = 30.095
    feet. @ 26.800, .75λ = 27.526 feet. which is it?
     
    #750 freecell, Jan 10, 2021
    Last edited: Jan 10, 2021

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