Antenna Tuner

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by K1JWJ, Sep 13, 2017.

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  1. W4IOA

    W4IOA XML Subscriber QRZ Page

    I bought a 994brt remote tuner for the base of the antenna and so far so good. Yes it has to be tuned at low wattage but takes a moment.
     
  2. W5DXP

    W5DXP Ham Member QRZ Page

    Here's the SWR result of an AutoEZ/EZNEC simulation for the G5RVjr. Are you going to install the autotuner at the coax/twinlead junction?

    G5RVjrT.gif
     
  3. WB6OZD

    WB6OZD Ham Member QRZ Page

    I will be using the tuner in the shack. My plan is that this wire is my quick & dirty antenna while I play around on the different frequencies and then decide what I want to erect for some specific frequencies. Like many others, I'm space constrained.
     
  4. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    I'm similarly space constrained but have a 55' telescoping tower immediately behind the house and a roof tower on the center of the roof, with three beams, three wire antennas, an HF vertical with radials and three VHF-UHF verticals (small)...it "appears" you have about the same space I do, just have to be creative.:)
    https://www.google.com/maps/place/1...bcaeabe12b7d21c!8m2!3d33.719307!4d-118.039531
     
  5. WB5YUZ

    WB5YUZ Ham Member QRZ Page

    Didn't follow previous posts carefully enough, disregard. Sorry.
     
  6. W5DXP

    W5DXP Ham Member QRZ Page

    I would recommend first trying reduced power on 30m, 17m, 15m, and, 12m because the necessary voltage on those bands may be high enough to cause your coax to arc. For instance, some RG-58 and RG-8x is only rated for 300 volts. If you try to shove 100 watts into that G5RVjr on 15m, the tuner will probably output 650 volts, just like my SG-230 does. If you are determined to run 100w on those four bands, you need to use a better grade of coax than the 300v rated stuff, e.g. RG-213 rated at 3700 volts. Ideally, the autotuner should be located at the antenna feedpoint or at least at the coax/twinlead junction. Maybe you should calculate the losses in the coax for those four bands.

    If you have room for a 90 ft dipole, I would recommend turning your G5RVjr into a ZS6BKW. However, 15m still will be a problem.
     
  7. W1VT

    W1VT Ham Member QRZ Page

    A lot of good multiband dipoles don't cover 15, so I'm currently using a dual band 15/20M dipole aimed N/S and a 15M dipole aimed E/W.

    Joel Hallas has published dual band coupled resonator designs in the October 2011 QST (p.48). More recently he has published a 10/15/20M coupled resonator design in the June 2017 QST (p47).
     
  8. WB6OZD

    WB6OZD Ham Member QRZ Page

    Lots of good points! I'll do some further research on remote tuner options. The info with the G5RVjr stated that it needed at least 70' of coax for the impedance matching, which is why I was planning on the tuner in the shack.

    Orignally, I wanted to do a ZS6BKW, but it would have meant running it East/West which is not really radiating in the direction I want. Plus, the wife isn't too happy about me wanting to string wires over the pool area (to the back fence) and along the side of the house. It would all be elevated, but not something she's happy about. Like I said, the G5RVjr is my quick & dirty option while I explore other solutions. Your suggestion of RG-213 is well heeded and I'll be sure to step up the quality of the cabling.
     
  9. AC6LA

    AC6LA Ham Member QRZ Page

    Cecil and other AutoEZ users: In a case like Cecil posted in reply #12, where you are modeling several discrete frequencies rather than a continuous sweep over a range, you can use a little trick to "self-document" the chart. On the AutoEZ Custom tab choose "Frequency - Column" rather than "Frequency - Line" for the X axis selection dropdown box. That will produce a chart like this:

    FreqCol.gif

    And here's a comparison showing the difference that 70 ft of RG-8X coax makes.

    FreqCol2.gif

    Dan, AC6LA
    http://ac6la.com/
     
    Last edited: Sep 13, 2017
  10. WB6OZD

    WB6OZD Ham Member QRZ Page

    Thank you both for the charts. I'll likely be installing with 100' of RG-213. I'll also be borrowing an antenna analyzer from a friend and will compare my results to what you've posted.
     

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