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Fact or Fiction ... Antenna tuners/meters for dummies (please help) Thanks

Discussion in 'CB and Export Equipment and Accessories' started by WINKDOGG, Nov 24, 2019.

  1. WINKDOGG

    WINKDOGG President CFO & CPFO WorldwideDX Radio

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    Hey guys I know this has been asked a million different ways in a million different places but I'm hoping to help myself and other CB skip shooters wrap their heads around tuners , swr (standing wave ratio) , meters and meter quality . That being said , I'm not claiming to be a real tech or electrical engineer but I have been skip shooting and talking local CB for around 25 years . I do most of my own basic tuning , mods and repairs as well as building my own antennas (for fun using a calculator and google) I have a general understanding of antenna theory and the basics but would love some of you techs, hams, even electrical engineers to put some things in plain English to put to rest all of the misinformation or miscommunication and misunderstanding about SWR , tuners and meters in general .

    Im leaving this post open for questions and answers but please no tough guy stuff or trying to make me or anyone else look bad for asking questions and trying to learn , thanks !

    MY MAIN QUESTION : I run an MFJ-941E antenna tuner with my Maco v-5/8 as well as my horizonal and vertical homemade wire dipoles . I was confused a bit the other day when a respected local said "your antenna tuner is just making your meter LIE to you " . I know with the tiny $20 tuners probably do just that "trick my meter" but I always believed a good heavy tuner with real open air capacitors will in fact TUNE MY OUTPUT TO MY ANTENNA . Maybe Im wrong but I know hams use this type of tuner and I tend to think hams are a bit more technical than most of us CB'ers .

    I also have run swr meters inline AFTER my tuner and the meters all read the same 1:1 after the tuner . So aside from the "true watts" discussion are AFFORDABLE meters reliable enough ? I have never blown the finals in any of my 40+ CB's regardless of how crappy my swr meter was , so I believe as long as its functioning properly any swr meter is certainly better than nothing and most are fairly accurate .

    So what do I / We need to know about tuners and meters in general ??



    Thanks as always in advance for everyone's input !!!

    Four-Two-Zero (not four-twenty) in the Garden State

    How Bout It DX Land ????
     

  2. binrat

    binrat WDX Club Coordinator
    Staff Member

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    I treat anything past the output of the radio jack a part of the antenna. Here is a video for your viewing pleasure. Lengthy but some good info.
     
    wavrider, WINKDOGG, Woody-202 and 2 others like this.
  3. Unit 75

    Unit 75 "TRAINMAN"

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    I can understand you using a tuner on your wires. Is there a reason your using the tuner with the Maco??
     
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  4. fourstringburn

    fourstringburn W9WDX Amateur Radio Club Member K5KNM

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    Tuners don't really tune antennas, they compensate for any mismatch in or along the antenna system.

    Your Maco antennas is tuned by lengthening or shortening the antenna to the closest resonate point ideally where you operate at. You then rely on the antennas bandwidth to operate on either side of that.

    A tuner can lower the SWR outside of the antennas sweet spot so it looks good on a SWR meter, but the actual SWR at the antenna never changes.

    We Hams use tuners on multiband antennas so we can operate our radios safely beyond the resonate point on many of those multibands.

    On 80 meters with my multiband wire antenna, my actual SWR at the antenna feedpoint is as high as 10:1 or more. The ERP (effective radiated power) isn't very good and my radio's high SWR protection circuit will kick on if I tried to operate it like so.

    But because I use a tuner, I can get a low SWR so my radio will transmit full power but the true radiated power out the antenna is about a 65% power loss due to in-efficiency losses. So, on 100 watts, I still can transmit 35 watts with an inefficient antenna. I also use an amp to boost the power so my approximated ERP is increased before any other typical losses are calculated. There are always other some losses in your antenna system but many are small.

    Your SWR meter can show full power out from your radio and a flat SWR on the tuners meter. All this means is that you have a nice match in your antenna system before the antenna and your radio will be capable of full output power. However, it doesn't mean your transmitting full power out the antenna. The losses are dissipated out the antenna as heat and not effective radiating RF.

    Ideally, tune your antenna with a analyzer at the antenna feedpoint for the best ERP and you shouldn't need a tuner with a monoband antenna. Tuners can have losses in them too.
     
  5. 543_Dallas

    543_Dallas Sr. Member

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    Reflected power that isn't lost in the tuner or feedline as heat will radiate eventually. There's more going on than protecting the radio from a mismatched load. The video binrat posted is a good one.
     
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  6. fourstringburn

    fourstringburn W9WDX Amateur Radio Club Member K5KNM

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    True,

    I refer to it like putting your thumb on a garden hose. All the water eventually comes out but only the stream goes where you want it and some of the restricted water dribbles out the opening.

    I'll watch the video.
     
    WINKDOGG likes this.
  7. Road Squawker

    Road Squawker Sr. Member

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    "Tuners" do not tune the antenna. the SWR "looking into the antenna" doesn't change.

    they also do not tune your radios output, it is a constant 50 ohms (+/-), they only allow your radio to load into an approx 50 ohm load.

    If that is the case, why do you have a tuner in line?
    The "tuner" is just "seeing" the meter, not the antenna. take that meter out and see what the antenna impedance really is.

    Doesn't your MFJ tuner have an SWR meter built in?
     
    #7 Road Squawker, Nov 24, 2019
    Last edited: Nov 24, 2019
    WINKDOGG and Shadetree Mechanic like this.
  8. M0GVZ

    M0GVZ Sr. Member

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    Indeed it will and usually from the outer braid of the coax where you don't want it which is the reason many people set off things like neighbours burglar alarms or interfere with their TV.
     
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  9. Shockwave

    Shockwave Sr. Member

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    When your antenna is not tuned to 50 ohms, you see a higher VSWR because it no longer matches the impedance of the coax or equipment after it. The location of the mismatch in impedance is where signal loss occurs. While you can correct the impedance mismatch at the radio end with a tuner in order to satisfy the radio and allow it to make full output, you cannot remove most of the loss in signal unless the correction takes place at the antenna end, before the mismatched signal passes through 50 ohm coax.

    Coax works best when used with antennas that can maintain close to a 50 ohm impedance over the operating bandwidth. When using antennas that will operate well outside of that impedance range, balanced ladder line feeders are the best choice since they will not have nearly as much loss when the VSWR and impedance are corrected with a tuner at the radio end.
     
    #9 Shockwave, Nov 24, 2019
    Last edited: Nov 24, 2019
  10. Mustang 131

    Mustang 131 Sr. Member

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    The closer the match is to the feedpoint, the better.
     
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  11. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    The benefit of a remote tuner.
     
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  12. Road Squawker

    Road Squawker Sr. Member

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    Many people don't realize that the (say) 1.2 dB loss/100 feet that is on coax rating charts is calculated into a 50 ohm load.......

    feeding a high impedance load, that 1.2 WILL be much higher.
     
  13. kopcicle

    kopcicle Sr. Member

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    that would be an understatement
     
  14. kopcicle

    kopcicle Sr. Member

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    I'm going to drastically simplify
    Resonance and feed point impedance can be and generally are unrelated.

    I have several wires and one vertical that are resonant at several related frequencies.
    Two of the wires are stub matched at the feed point to get close to the feed line impedance.
    One of these antennas is a 34' vertical with a SGC SG-230 at the base.
    (this effectively removes this system from the discussion)
    None of these antennas have a feed point impedance of 50 ohms .
    The wires don't come close to 450 ohms or even 600 ohms.
    The one wire that comes close is the 80m OCFD but it's feed point impedance is all over the place.
    I accept a bit of feed line mismatch for frequency agility while using a tuner to keep the radio happy and deliver maximum energy to the feed line.
    In my case a Drake MN2700B. This is a Pi-L type tuner and provides a measure of low pass filter function as well.

    Resonance and feed point impedance can be and generally are unrelated.
     
  15. wa373

    wa373 New Member

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    One question posed by the poster is how accurate are "affordable" swr/power meters? I would consider "affordable" as between $100 to $150. :cautious:
     
    WINKDOGG likes this.

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