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5/8 Wave groundplane 1.5:1 SWR all over the band

Discussion in 'CB Antennas' started by mattsowders1989, Dec 4, 2019.

  1. 2NC995

    2NC995 WDX995 / DAN

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    Right, but that’s my point...an antenna analyzer is not something most CBers are using.


     
    Shadetree Mechanic likes this.

  2. The DB

    The DB Sr. Member

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    On a mobile antenna, you won't notice the difference between the low SWR point and the self resonant point. But you also won't notice the difference if you are outside both of said points and still under 2:1 SWR. If you want to get the antenna to the lowest SWR possible, more power to you, it won't hurt anything, but you won't gain anything by it either.

    With some base antennas this may not be the case as they have matching circuits that can tune any number of configurations to a very low SWR simply by adjusting the matching circuit (aka the Maco V5/8 antenna where you can adjust the tap on the ring).

    This being said, this isn't the nature of this discussion. There are other dynamics added in, such as the requirements of the op's amplifier. There are also several sub discussions around other things that have come up.


    The DB
     
  3. 2NC995

    2NC995 WDX995 / DAN

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    I would gain the satisfaction of knowing my equipment will be happy with the low SWR, and that’s important to me. I don’t think I’m obsessive about it, but putting the low dip in the middle is a very simple matter, and ensures the load is as good as it’s going to get across what ever range I plan to operate.

    Im definitely not a believer in the “way we’ve always done it” mentality, but speaking for myself, I don’t plan to avoid an extremely simple adjustment that will let the equipment run in the “happiest” part of the curve.
     
    #63 2NC995, Dec 16, 2019
    Last edited: Dec 16, 2019
    Shadetree Mechanic likes this.
  4. undertaker

    undertaker Undertaker

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    I have an mfj 259 b good investment if you are going to playing with antennas..
     
    #64 undertaker, Dec 16, 2019
    Last edited: Dec 16, 2019
  5. 2NC995

    2NC995 WDX995 / DAN

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    Something I plan to buy, but more for making my own antennas than setting up out of the box type things. I’ve been reading reviews on various models for months, haven’t decided how to spend my dollars yet!

    I tend to think that for most CBers, using commercially manufactured antennas, that adjusting via SWR is more than satisfactory. But...always wanting to learn more.
     
  6. Marconi

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

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    I agree DB.

    Using a typical CB radio that only covers 40 channels (0.44 KHz of bandwidth curve) will likely never show the real truth of resonance...just using their radio to measure.

    At best they might see a straight horizontal line or one with a little slant to one side or the other, but it will not look like a curve.

    IMO, this is why many CB operators say their SWR is flat.
     
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  7. magnuman

    magnuman Well-Known Member

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    If you solder the Coax directly to the antenna it makes it difficult to measure the resonance and SWR of the "antenna alone" which is important to maximizing efficiency.
    You can tune a non resonant antenna to show a low SWR by changing the length of the coaxial cable. Losses in the cable frequently make the antenna appear better than it is.
    Stick you SWR meter directly under the antenna and tune from there. It is much easier with a plug on the end of the cable and Antenna!
     
  8. Marconi

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

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    Good point magnuman.

    I think this member was lucky he checked closer to the ground before he had to take his antenna all the way down. Maybe it would have been more convenient had he direct connected all of his connections in the system. Maybe the bad jumper had a bad connector too?
     
  9. Jaydean

    Jaydean New Member

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    I have the same antenna. It is the newer version purchased from Strictly Ham in Australia. Mine is exactly the same, I cant get the SWR below 1.5 to 1. I replaced the matching system with copper as the drawn aluminium one is very brittle and eventually breaks. Good antenna but I also would like to get the SWR down a bit more.
     
  10. Road Squawker

    Road Squawker Sr. Member

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    Well, if it really is that important to you, you can always put the meter at an even multiple of a 1/2 elect wavelength and get a valid number.
     
  11. magnuman

    magnuman Well-Known Member

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    That is True......
     
  12. M0GVZ

    M0GVZ Sr. Member

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    That is caused much more by the fact there's common mode RF on the coax so the coax is forming part of the antenna and is also radiating as an antenna too. You alter the length of the coax and you're effectively altering the length of the antenna.
     
  13. kopcicle

    kopcicle Sr. Member

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    well let's see...

    no endorsement implied . A bit more information than a MFJ259C can supply:
    https://www.aliexpress.com/item/400...chweb0_0,searchweb201602_3,searchweb201603_53

    then

    http://www.hamskey.com/2017/12/adding-bluetooth-module-to-mini-vna-tiny.html
    Curiouser and curiouser said Alice...
    Seems a hack that could be applied various places.

    http://www.w5dxp.com/notuner/notuner.htm

    [​IMG]

    Although ladder line and not coax you get the idea.


    Anecdotal:

    I use a SGC SG-230 auto-tuner for this monstrosity in the back yard.
    e33ff22607f7d1b3b5eb70a96edb8f8032955a76-1.jpeg e37492a671b2a6fd613c164799199bbcf2d98bd3-1.jpeg

    I've used it to great advantage on multiple antennas. There are two related "gotchas"
    however. It does not like to tune half wave radiators or multiples of half wave wave transmission line , in coax or ladder line. It hunts or just goes stupid on occasion.
    Otherwise it has offered zero issues in ten plus years.

    @mattsowders1989 , it doesn't really apply to your situation but it's where the thread drift took us :)
     
    2NC995 likes this.
  14. Rick330man

    Rick330man WDX 404

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    "Remember what the door mouse said: 'feed your head.'"
     
    wavrider likes this.
  15. Chris Cross

    Chris Cross New Member

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    You don't really get SWR? picture your lungs, when your radio gets a signal its like breathing in, when you key up to talk it's like exhaling, now instead of exhaling with ease you have air blowing at your face like a car going 65mph and your head is outside the window. Your signal feeds back into your radio getting into the way of the other signal trying to leave. Your radio will work and in time your finals will have a much shorter life, if you match your antenna to a 1:5:1 at the most your signal will have a lot more punch and go further.
     

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