High SWR on G5RV

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KE5UKI, Aug 2, 2008.

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  1. KE5UKI

    KE5UKI Ham Member QRZ Page

    I'm running a Yaesu FT-450AT with a built in automatic antenna tuner. It is connected to a RadioWavz G5RV antenna with an air-balum choke at the connection of the coax and feed line. The antenna tunes up fine on 80, 40, 15, 12, and 10 meters, with SWRs in the 1.1:1 - 1.2:1 range. But, it will not tune on 20 meters. My understanding is that the G5RV is resonant at 20 meters and thus should be the most likely band for the antenna/radio to tune on. But I cannot even measure the SWR on 20 meters as the meter is pegged.

    Anybody have an idea as to why my antenna will not tune on 20 meters.

    Something else that's strange, I've worked some of my farthest DX on 20 meters even though the SWR is out of sight.

    John, KE5UKI
     
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    ::I wouldn't trust the SWR reading from the FT-450 in this case. Here's why: If the SWR is above 3:1, the FT-450 transmitter shuts down entirely and produces no output power at all; thus, it's impossible to work DX, or really anything else, if the "SWR is out of sight."

    Something's wrong, there.

    WB2WIK/6
     
  3. AG3Y

    AG3Y Guest

    I certainly agree with Steve. I would put an external SWR meter in the line and see what it reads. There is something amiss with your internal metering ! You should check the SWR on the line itself, on the antenna side of the tuner to see if the antenna is, indeed, resonant, or not.

    Good luck ! 73, Jim
     
  4. K8AG

    K8AG Subscriber QRZ Page

    G5rv swr

    Hi John,

    I have a homebrew ZS6BKW antenna. The ZS6BKW is a derivative of the G5RV and exhibits lower SWR on most bands (even some WARC bands). I have an FT920 and it works well with the internal tuner 80-6 except for 75, 30 and 15. It also has been pretty good in performnance. My current record is 6000 miles per watt.

    FWIW

    73, JP, K8AG
     
  5. G0GQK

    G0GQK Ham Member QRZ Page

    The ZS6BKW is not the same as a G5RV. It was designed by a station who is now G0GSF. Its a different length so its an entirely different dipole.
    see www.reflections.co.nz/index.php/archives/43
    then go to ZS6BKW antenna revisited from sprat #129

    Its a far better antenna.

    How you are able to load up all these bands from an internal ATU is a mystery.
    I think on some bands the power output must be about 10 watts, but as the G5RV was specifically designed for 20 metres in 1946 and not for 10, 12,15, or 17 metres because these were not ham bands in 1946 defies logic

    G0GQK
     
  6. KR2D

    KR2D Ham Member QRZ Page

    Why is it a mystery? When I had a G5RV, the tuner in my IC-746Pro would match it on all bands 160m to 6m.
     
  7. K8AG

    K8AG Subscriber QRZ Page

    Zs6bkw

    The ZS6BKW was based on the G5RV, but it was optimized using a computer (for what that is worth).

    As for matching all of those bands, rigs like the FT920 list a max SWR as 3:0, however my guess is that depends on bands.

    It is quite a bit shorter than the G5RV (90' vs 102'), but I have found it very convenient covering a lot of bands well enough.

    73
     
  8. AG3Y

    AG3Y Guest

    But how well did it work? I can match my transmitter into a 50 ohm dummy load without a tuner. But I sure wouldn't want to try to WORK ANYBODY with it ! :eek: :rolleyes:
     
  9. W5DXP

    W5DXP Ham Member QRZ Page

    Using an antenna analyzer, what is the impedance seen by the tuner on 20M?
     
  10. N3JJB

    N3JJB Ham Member QRZ Page

    The ZS6BKW is not the same as a G5RV. It was designed by a station who is now G0GSF. Its a different length so its an entirely different dipole.
    see www.reflections.co.nz/index.php/archives/43
    then go to ZS6BKW antenna revisited from sprat #129


    I had my doubts, but built one of these anyway. No tuner on 6 bands.
    Also, keep in mind that when using a tuner, unless it's out at the antenna, there is high swr on you coax. So if you're using a g5rv what your swr meter says is usless. It only tells you whats happening at the radio not out at the antenna.
     
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