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. WA7ARK

    WA7ARK Ham Member QRZ Page

    Using EzNec and AutoEZ, here is a sim of a 43ft 2in dia aluminum pipe standing on 8 30ft radials. (Let me know if yours is a lot different than this).

    First, here is the predicted feed-point impedance R and X at selected frequencies:

    43z.png

    On 60m, the pole is almost 1/4 wavelength (nearly resonant), so would almost match by switching out the tuner.

    I then asked AutoEz to compute a low-pass L-network to be inserted at the pole base to convert the R and jX above to 50+j0 at each of the frequencies. The K column is the required shunt capacitor in pF; the L column is the required series inductance in uH. The M column tells us if the configuration of the L-network; capacitor at input or capacitor across the feedpoint.

    43l.png

    Notice that on 80m and 60m, the required capacitance is large, likely more than your auto-tuner can supply.

    You could fix this by using a relay to switch in an additional fixed capacitor across the tuner input only on 80m and 60m.
     
    Last edited: Nov 7, 2018

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