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Question on the Vector

Discussion in 'CB Antennas' started by The DB, Sep 15, 2014.

  1. Shockwave

    Shockwave Sr. Member

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    I wasn't aware that this design defied collinear gain theory. For if it did all collinear antennas that used the common folded phasing stub would also be defining collinear gain theory since they do not add any extra spacing between elements either. I also don't believe all of the gain comes from the simple idea of a 1/2 wave over a 1/4 wave. Far too much change in the distant signal can be seen by making small changes in element lengths for me to ignore the likelihood that beam tilt is also possible with this design.



    Simply lengthening the radials forming the basket causes the signal feeding the upper 1/2 wave to be delayed with respect to currents on the cone. Bob did this, I did this and so did Sirio a few years later in the new Vector. Just a few degrees of delay and we have downward beam tilt. This is a change that cannot be seen locally. All of my testing was done with a vertically polarized FM station transmitting approximately 30 miles away.
     

  2. jazzsinger

    jazzsinger Bullshit Buster

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    It would be very very hard to guess what the signal difference would be between two very similat 0Dbd gain antennas at fullwave spacing and similar height with similar coax.

    The part of the picture you are missing out is there may be multi signal paths on both antennas, all of varing phases, now depending on different obstacles, natural or man made you also have reflections/refraction all coming into play which give peak spot and blind spots and all sorts of spots inbetween.

    Assuming for a minute there is only one path on each antenna and a massive obstacle in the path of one antenna and nothing in path of other it pretty obvious what one will win. But take a look at the double slit experiment and all of a sudden you realise there will be peaks and troughs and allsorts of paths going on, all it takes is for a high sided lorry to move and you've lost or gained on that path depending if it was blocking, reflecting or refracting that path.

    All double mast comparisons suffer this flaw and thats before you even consider the changing nature atmospheric conditions add to wave propagation.

    I wouldn't say dual mast comparisons are cb bullshit, more they introduce far too many complications for accuracy.

    I remember once sitting in hills above Glasgow in qso with a 68 div station late at night line of sight, something I could repeatedly do from that very high location nightly, he had a moonraker 4 pointed right at me, he was giving me s6 and I him s4, we moved the car approx 2 feet as tail end was sticking out a biit on single track road, he jumped to s9 and I to about s6, I ain't suggesting a 2 ft move gave me a 2 s point increase in every direction, justhis, I probably lost signal in many other directions, but it shows how a tiny movement can affect signal path and either reduce multipath cancellation or arrive in phase and give addition, that was only 2 feet, can you imagine the difference in terrain over a 36 ft gap to a statio 30+ miles away, incidently io'm about 30 miles from the coast and then lies the irish sea before I hit 68 div and he was a good 10 mile inland.Inbetween some very rough and high terrain.

    the terrain and path changes between those two antennas could be enormous, one antenna could get there easily and too another he lies in a blind spot he can either barely or not hear. Its a total lottery. Put both antennas on same pole you've taken all those factors out instant, signal paths are all the same, especially if you change over fast, coax is the same, mast is the same. Results will be a lot more meaningful.

    I ain't seen any antenna tests done like that, nor have i seen any that use a calibrated step attenuator and a digital voltmeter/uv meter to measure accurately the signal difference, all rely on heavily innacurate s meters.

    I just look at the bigger picture Eddie.
    Jazz 73
     
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  3. Marconi

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

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    Well Jazz, do you really think it impossible for CBr's to make some fairly good conclusions about antenna performance, testing TX/RX signals using our relative radio meters?

    If so Jazz, do you really think using high tech equipment is the only way to really test and compare what we want to know in this regard?

    Do you think if we turn our RF gain down to close to zero...we can tell a little better...or is the cut back (receive gain) circuit still functioning to make all signals more well rounded and balanced...so to speak?
     
  4. jazzsinger

    jazzsinger Bullshit Buster

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    Hi Eddie.


    I wouldn't say its impossible to make antenna comparisons. I just think its very hard to make accurate measurements, especially using seperate masts.


    the s meter will show relative increases/decreases of signal levels but not accurately. Backing it right off could be as bad as having it fully open.


    Most s meters are logarithmic voltmeters (may not be case on digital ones) as are swr/power meters and generally the most accurate/most linear part is mid scale where the divisions are spaced more evenly, at the low end they are very far apart and high end heavily compressed.


    When you add an extra mast you completely change propagation paths. That makes comparison more dependent on terrain than antenna, if done on same mast terrain stays the same as do all other parameters. Much more meaningful results. Steady signals also help.


    I'm not a believer of same tip heights or i max heights. Its a test of design so mounting location/feedpoint is part of design so should be the same on all antennas.


    If you have to add another 9 ft of mast to make tip or i max the same your measuring an antenna against an antenna and mast extension. Its the design your testing so if feedpoint is high or i max low its more a design flaw in my opinion.


    it all comes down to how accurate you want your measurements and how important it really is to you. It also depends on what you class high class tools which I don't think are necessary to realise which antenna is better but if you want to know by exactly how much then quality test equipment is essential.


    I'm quite happy to use stardusters,penetrators,sigma 2/4, astroplane,mighty magnum 3,vector 4000, top one,clr2,tornado, 827 or any other decent design as all will do the job well i use them for which is mainly skywave dx.


    I don't really care if ones a fraction of a s point up on the others, all are proven performers and chances are no-one will notice it.


    Jazz 73
     
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  5. Marconi

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

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    Jazz, I can't disagree with anything you've said here, including your conclusions.

    The mistake I made is trying to show you guys what I did and how I did it.
     
  6. Knight rider

    Knight rider New Member

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    Hey fellas I'm new here and im sorry if im in the wrong section. Which is the best cb antenna, the gain master, I max 2000, or a moon raker type? I have a 5 element verticle beam but the elements got bent and I need to replace em, but until I do I am looking for another antenna. Thanks for the help in advance.
    KR,
     
  7. Marconi

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

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    Welcome to the forum KR. I like the Gain Master, because it is effective and I find it works great in the CB band and has very little to no TVI type problems...in 11 meters. I've had mine up about 40' feet to the feed point for 2 - 3 years now, and I think it is holding up well, but I live in a mild weather area too.

    I have 3 sets of guys lines and I set them with a bit of slack so the wind works on the mast and the antenna together. IMO this takes the load off of the antenna a bit.

    Good luck and keep us posted.
     
  8. Knight rider

    Knight rider New Member

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    Thank you Marconi for your reply, I see what your saying about the slack in the lines. For a little extra money I think I will ease my mind and choose the gains master. There is so much to learn about this, but I feel like I have joined the right place to get the knowledge.
     
  9. Marconi

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

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    Just a note. The mounting brackets that came with my Sirio Gain Master broke the first time I tried to remove then from the mast I had attached them to about a month or two after I first installed it. The threads in the nuts or the u-bolts were messed up probably from the wind. They did not break while installed, but when I tried to remove the antenna from the mast. I use a couple or three fence/gate brackets and they have never failed me.

    See image below.
     

    Attached Files:

  10. sdmahr

    sdmahr Active Member

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    I've used those fence brackets with great results. MUCH stronger and a better grip that cheap chinese u-bolts.
     
  11. Needle Bender

    Needle Bender ...he thinks it's funny that I stepped in it

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    Makes sense to me. As I believe this to be an off-center fed full wave vertical with the bottom 1/4 OR SO inverted (folded up) to capture it's next 1/4w up and to radiate a bit itself, though the cone top would be a voltage not a current node, it should show a little additional radiation.
    I doubt your 30 mile test as that's well over the horizon and well past the point to be seeing 'ground wave'. I suspect D layer reflection showing the opposite. Seems shortening the cone should move the upper 1/2w toward a 5/8 radiator lowering the TOA, unless you're also moving the feed point of the Gamma.
    Have you used near-field measurement to test for lower TOA when lengthening the cone?
     
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  12. RetroGrouch

    RetroGrouch New Member

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    I know its old by this deserves another look.
    This has got to be one of the best posts I have read anywhere ever
     
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  13. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    That is interesting, does the feed point of the gamma affect the radiation angle? Or am I reading this wrong? Just trying to learn.
     
  14. The DB

    The DB Sr. Member

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    When referring to the near field, or in the case of this post anyone in local contact range, then yes the angle of radiation can be changed by modifying various dimensions of the antenna. Bob85 has reported this as well as I think one or two others, and modeling also shows that this is possible, which shows a wide range of angles the antenna can be adjusted to radiate towards. I do not know offhand which changes made how much of a difference in this angle offhand, but it does exist.

    However, when referring to the TOA, as it applies to DX, that angle does not change when changing various dimensions on this antenna as it is based on how high a certain part of the antenna is and the quality of the earth below.

    Using D layer reflection as Needle Bender suspects to get a contact 30 miles out would be NVIS territory. NVIS requires a much lower frequency than CB uses to work.

    On a beach, looking out over the ocean, an average adult can see about 20 miles out. However ships of old had something called a "crows nest". What benefit did that give crews of ships? To see further out. Applying this to antennas, even at 30 feet, an antenna is high enough to "see" an antenna 30 miles away, which requires no propagation to communicate from one antenna to another as they are line of sight (unless of course their is something like a hill in between).


    The DB
     

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