Getting 80m and 30m bands from my 43' vertical?

Discussion in 'General Technical Questions and Answers' started by KI1SPK, Nov 6, 2018.

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  1. KI1SPK

    KI1SPK Ham Member QRZ Page

    Hi everyone,

    I made my own elevated 43' wire vertical with radials. It seems to be performing pretty well with an LDG RT-100 tuner on 40m, 20m, 17m. No complaints there.

    It will not tune on 80m and has a very difficult time tuning on 30m.

    I don't think I would be too active on 80m and 30m anyways, but I was expecting 10-80m with the LDG RT-100.

    I am doing something wrong? Any thoughts?

  2. WA9UAA

    WA9UAA Ham Member QRZ Page

    Might simply be a hard length to tune. The first thing would be to look at the antenna with an analyzer. The analyzer and a bit of experience might tell you how to modify the antenna with a change in length or adding some reactance to make it resonant. 73,
  3. K0RGR

    K0RGR Premium Subscriber QRZ Page

    Are you using a balun or unun to feed the vertical? My MFJ 43 footer uses a 4:1 balun.

    My 43 footer has an SWR of just under 5:1 on 80. That might be a bit too much for an autotuner, though the internal tuner on my old IC746 handled it well (my LDG tuner does not). With a wide range tuner, it works poorly on 160, too. There are designs out there for switchable loading coils to resonate the antenna on 80 and 160 for improved performance. It should work fairly well on 60 meters, too, and it's a 1/4 wave long there.

    On 3o meters, the autotuners handle it OK.
  4. K8JD

    K8JD Ham Member QRZ Page

    Some Ideas on the 43 ft Vertical
    To try using all bands you need to have a remote operated tuner(weatherproofed) right at the feedpoint on the bottom of the vertical element. You have to add some series inductance to use this antenna below 5 MHz. Using a tuner at the radio end of a long coax feeldine is not very efficient. On the bands higher in freq than 14 mHz, using this antenna will result in a lot of wasted energy in high angle lobes.

    That 43 ft length is actually a 5/8 wave on 20M for the maximum low angle signal on the most popular ham band , also happens to be near a QW length on 60 M, maybe the least popular band. :D
  5. KI1SPK

    KI1SPK Ham Member QRZ Page

    Thanks for the replies,

    I am not using a balun/unun at the feedpoint, as I was worried about loss there. I have a ferrite choke at the shack to try to block common mode currents.

    The tuner is remote operated, right at the feedpoint, which is why I am a bit surprised it wouldn't tune 80m, and has a very difficult time with 30m .

    Btw, is there much action on the 60m channels?
  6. K8JD

    K8JD Ham Member QRZ Page

    I can just imagine :rolleyes:
    Joe Ham taking a hacksaw to this $500 piece of aluminum pipe !!! :eek:
  7. K8JD

    K8JD Ham Member QRZ Page

    Yes plenty of SSB and DIGI and I am CW only on 60m.
    I have worked all states except for AK since the 60 M band was opened to CW.
    I have worked about 175 SKCC members and earned the single band C and T endorsements for 60M from SKCC also !
  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    On 30m, the problem is likely the feedpoint impedance of a 43' monopole is so high the tuner just can't find a match. Its length is about 170 degrees; at 180 degrees, the feedpoint impedance (Rr primarily) is thousands of Ohms. Tough job for a tuner without using a balun. I'd probably choose at least a 9:1 balun for this (higher ratio is likely better).

    Of course, you'd want to ditch the balun on 60m, where the same monopole is about 90 degrees and likely about 35 Ohms feedpoint impedance.:)
    WA9UAA and WA7PRC like this.
  9. N0IOP

    N0IOP Ham Member QRZ Page

    I just ordered the parts for a base loading coil for 80m and 160m operation on a 43' vertical that I'm in the process of installing.

    You may find this writeup insightful:

    The parts cost is presently around $100 with the coil and the relays being most of the cost. I'm using Omron MJN3CF-DC12 relays, $22 each from DigiKey, which have 600 volt contacts and a 2,500 volt dielectric strength between contact sets and between the contacts and coils. The air coil from MFJ is $38.
  10. N0IOP

    N0IOP Ham Member QRZ Page

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