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Antenna Tuner Questions

Discussion in 'Ham Equipment' started by Riverman71, Sep 30, 2018.

  1. Riverman71

    Riverman71 Part-time Member

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    I know the function of an antenna tuner is "reduce" the actual SWR to an acceptable level in the eyes of the transceiver so it does not restrict its power output. And that the actual SWR, in reality, does not change.
    What I would like to know is this:



    1. For owners of the following transceivers, how high of an SWR can your internal tuner effectively handle?
    a. Kenwood TS-590SG
    b. Icom IC-7300
    c. Yaesu FT-991A or FTDX-3000 or 1200

    2. For owners of an external tuner, how high of an SWR can it handle? (Please denote Brand/Model).

    Thanks!
     

  2. 543_Dallas

    543_Dallas Sr. Member

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    I have an ftdx1200. The internal tuner runs out of range somewhere between a 4:1 and 5:1 vswr.

    I have a Murch UT2000a that I have used with antennas that measured 18:1 with my mfj antenna analyzer. Coax loss was extremely high in this situation and the antenna was not a great performer. With this tuner I have used my 5/8 wave cb ground plane on 20 thru 10 meters.

    What matters most to the tuner is the impedance it has to work into. That varies with feedline length if everything in the system is not of the same impedance. A high impedance load creates a high voltage situation and can cause arcing. When feeding a low impedance load, like a short antenna, the tuner has to carry a lot of current. Light duty component overheat, loss is high and things might even melt.

    Tuners do more than fool the transmitter. The matching device in a half wave antenna or 5/8 wave antenna is basically a fixed tuner. When we move that tuner from the antenna feedpoint into the shack we can still get a good match but efficiency is poor due to the coax loss. Coax loss skyrockets when the the swr is high. I have felt rg213 get hot with a few hundred watts when the swr was high.

    Ladder line does not have this problem. If you use heavy enough feedline the only losses you have to worry about is the tuner. Use a good tuner and you'll have a very efficient doublet that can be used on all HF bands.
     
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  3. L2

    L2 Member

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    IC-7300 3:1
    LDG AT-1000 Pro II 10:1
     
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  4. w9cll

    w9cll W9WDX Amateur Radio Club Member

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    LDG IT-100 10:1 range
     
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  5. jon666

    jon666 Sr. Member

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    LDG IT-100 10.2 range
    last time i had my 7300 in shop right now its in storage):
     
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  6. BenMara

    BenMara W9WDX Amateur Radio Club Member

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    Palstar AT4K 30:1
    Impedance: matching range 20 Ohms to 1500 Ohms
     
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  7. Mudfoot

    Mudfoot Sr. Member

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    MFJ-939 Matches 6-1600 Ohms (SWR up to 32:1) -- that’s a 50% wider matching range than competing products that are less capable and higher priced . . . and it’s made in the USA.
     
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  8. Riverman71

    Riverman71 Part-time Member

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    All of the SWR charts I find stop at 10:1 with an estimated 66% power loss. Is it practical and/or worthwhile to even bother with a SWR of 20:1 with a good tuner?
     
  9. Mudfoot

    Mudfoot Sr. Member

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    Sure, if that's all you got, want to talk and your tuner can handle it.
     
  10. 543_Dallas

    543_Dallas Sr. Member

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    It might match a 6 ohm load but that gets harder to do with a tuner rated for more power. 200 watts at 50 ohms is 2 amps. 200 watts at 6 ohms is almost 6 amps. I would imagine to find some light duty parts in that tuner and that it would be very lossy at 200 watts into a 6 ohm load. It might even fail.

    Remember this is rf current not dc current. Because of the skin effect the conductor rating will be less than if we were using dc current.

    For a legal limit tuner. 1512 watts into 50 ohms is 5.5 amps. 1500 watts into 6 ohms is almost 15.9 amps. Same current as 12,640 watts into a 50 ohm load.
     
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  11. Riverman71

    Riverman71 Part-time Member

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    Ah! That would be me. :D
     
  12. Road Squawker

    Road Squawker Sr. Member

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    theres a reason they stop there,.... Jus Sayin;)

    Its not only about the tuner losses.
    Coax is rated in db loss per 100 feet when operated into a 50 ohm load (or whatever other characteristic impedance the coax may have).

    operating into a 20:1 vswr will result in unacceptable loss by the coax itself.

    IF you insist on operating that way, at least use ladder line, preferably 600 ohm.
     
  13. Riverman71

    Riverman71 Part-time Member

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    I'll probably wind up getting a new radio (been wanting one) with an internal tuner and sticking to the bands that tuner can handle.
     
  14. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    It is far better to stick with an antenna that presents a decent SWR or somewhere close enough that the tuner is only needed to tweak it a bit on the band edges if need be.
     
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  15. Riverman71

    Riverman71 Part-time Member

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    Got it.

    My list of contacts would be pretty short calling CQ while operating QRP with a SWR of 25:1 made manageable with a good tuner. And 50' of RG8X. And the current solar conditions. :D

    BUT, if I did make one, it would be, as the Beach Boys say, Fun, Fun, Fun!
     

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