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Help understanding my antenna analyzer

Discussion in 'CB Antennas' started by Magard, Sep 21, 2020.

  1. Magard

    Magard New Member

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    So low resistance isn’t a big deal if swr is under 2


     
    Tallman likes this.

  2. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    (y)(y)(y)(y)(y)(y)(y)(y)(y)(y)(y)(y)
     
  3. Magard

    Magard New Member

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    So I figured these antennas out..... mirrors weren’t grounded to the doors. So now I got something that I can work with. So Swr is 1.08 potential. Ohms is 50 potential and resonance is 26.401
    At the moment. What I’m asking is if everything is wanting to work. What should I be tuning for optimally. I am at 1.12 swr at my normal frequency of 27.335. 45 ohms.
     
  4. 144inBama

    144inBama Electricity doesn't kill you, ignorance does.

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    If I'm understanding this correct.... you're resonant @ Freq. 26.401? If so, that means you're resonant on the Super Low (band B) between channels 29-30....
    *edit to add*
    1.12 is a very good reading....a lot of people struggle for that good of a number.
     
    #34 144inBama, Sep 23, 2020
    Last edited: Sep 23, 2020
    undertaker likes this.
  5. BJ radionut

    BJ radionut Supporting Member and 6m addict

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    Magard: Usable the way it is...However the antennas are too long as rigged now.
    Do these have adjustable whips on top?
    If so, are they bottomed out or pulled up?
    If you shorten them, you will move the resonate frequency up.
    If they are bottomed out, you can "tweak" it a little more. I would start by cutting like 1/2 inch off each antenna Whip bottom push them all the way down...Measure again>
     
    Road Squawker likes this.
  6. BJ radionut

    BJ radionut Supporting Member and 6m addict

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    If those adjustable whips DO NOT bottom out into the fitting...Just move them down about 1/2 inch on each side ...Measure Again
    Mark where they are now with a Marker(so you can find that spot again)!
    Don't cut them unless they bottom out in the fitting...SOME DON"T
     
  7. Magard

    Magard New Member

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    Thanks guys. I understand tuning a antenna up or down the band. I’m really after understanding more than swr tuning. I would like to understand the graph part of this analyzer. R and x what does negative x mean
     
  8. BJ radionut

    BJ radionut Supporting Member and 6m addict

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    Antennas and Radiation
    https://www.sciencedirect.com/topics/computer-science/antenna-impedance


    Scroll Down to:


    Resonant Frequency and Bandwidth

    "The input impedance Zin of the antenna is a function of the frequency of operation. Figure 6.5 shows the magnitude of the input impedance of an example antenna as a function of frequency. In this case, the antenna impedance looks like a parallel RLC resonant circuit. The frequency, fr, for which the impedance magnitude is maximum, or equivalently the reactance is zero, is often defined as the resonant frequency. It is desirable to operate the antenna at this resonant frequency so that it can be easily matched to an input transmission line with a real characteristic impedance. The frequency span Δfr, beyond which the impedance magnitude falls below half of the resonant value, may be defined as the impedance bandwidth of the antenna. The antenna may be usable in this frequency band. Outside the antenna's bandwidth, the input power to the antenna would be significantly reflected due to impedance mismatch, resulting in poor radiation."...

    "In such cases, the resonant frequency is defined as the frequency of best performance and the bandwidth as the frequency span over which the performance can be tolerated, as dictated by the application. It is meaningful to call the resonant frequency and the bandwidth of an antenna with an appropriate parameter prefix, such as the impedance–resonant frequency, the impedance–bandwidth, gain–resonant frequency, the gain–bandwidth, ..."

    More: X (=0) the reactance tells you when the antenna "resonate" in that specific frequency. That is what you usually need first, to make the antenna resonant at a specific frequency.
    Then, when you got an antenna close to X=0, then you check R, the impedance, usually you need to go close to 50 Ohms. R=Z
    Z is the total impedance, from R + X. If you get R=50 and X=0 then SWR will be 1.
    Not all antennas are designed for 50 Ohms.

    https://ham.stackexchange.com/questions/13157/rigexpert-aa-35-interpreting-the-information

     
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  9. Magard

    Magard New Member

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    So here is where I tuned it. These are dual 5 foot power sticks Quad Wire set up. Guys in the know I’m sure have a better name for them. I guess legendary top load antennas. I believe these are good numbers. Just a little encouragement for myself and others that taking the task upon yourself can result in good results. You can’t pay for someone to dual a system in like this. I choose this frequency because it’s what I talk on most of the day. Channel 19 is still really good.
     

    Attached Files:

    Slowmover, S&W357 and Tokin like this.
  10. BJ radionut

    BJ radionut Supporting Member and 6m addict

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    Magard: It just does not get much better than that!
    Enjoy! Good Job(y)
    All the Best
    Gary
     
  11. Magard

    Magard New Member

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    I just talked 40 miles across a valley to another mobile. He was weak but said I was loud and clean. Finally got this radio like it should be.
     
    #41 Magard, Sep 24, 2020
    Last edited: Sep 24, 2020
  12. S&W357

    S&W357 $upporting Member N.C. WDX-556

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    Great report (y)
     
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  13. Tokin

    Tokin The Man With No Shoes

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    Take the BATTERIES OUT of your analyzer and put it up in a clean dry place until your next antenna set up. DO NOT SELL IT. Some folks sell them because they just sit around and then wish they hadnt when they set up a base station or a new mobile rig.
     
  14. M0GVZ

    M0GVZ Sr. Member

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    Contest winning contester here., SWR makes you stupid. I never bothered trying to reach 1:1.0 and in fact I ran SWRs 10,20,30 or more times that at the antenna feedpoint using wire antennas multiband. Modelling my inverted L antenna fed by a SGC230 that was 85:1 SWR at its highest on one band, it could hear a gnat fart on the other side of the world, didn't stop me working the world, being told I was the loudest station in Europe on 40m during a contest where I was running a frequency with just 100W.

    As long as it was below 1.6:1 for transmitting, enough to keep the transistors in the PA happy (which is what the SGC matched it to), it was good to go and on valve gear I'd push it to 3;1. You'll notice no difference in receive or transmit by getting lower than that.

    Right now thats over back to the analyser.

    First point is you need to be connected to the antenna as near to the feedpoint as possible so that means using as short a length of coax as you can. If you can't do that you need to ideally be using an ELECTRICAL half wavelength of coax as the end of that will give you figures the same as the antenna end.

    You want to be looking at TWO different sets of figures.

    First you need to look at is what the feedpoint impedance (Ohms) is when Z=0 so scan around the results until you find where Z is the lowest or nearest to zero and read out the Ohms. That will tell you how efficient your ground plane is. A quarter wave over a perfect ground has a feedpoint impedance of 36.8 Ohms at resonance (where Z=0). The further away from that the more ground losses you have.

    Second one is your SWR. The SWR dip will be in a different place to where the Z dip is. You want this to be below 1.6/1.7:1 on a CB and ideally you'd see 50 Ohms at that point but if you're using the coax that came with the mount you may see a reading different than that due to the effect of the coax..
     
    #44 M0GVZ, Sep 28, 2020
    Last edited: Sep 28, 2020
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