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For elevated radials.

If I put up a 40m/80m fan vertical can I do the same for radials, that is cut some for quarter wave on each band?

Radials will be about 2m off ground.

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Short answer: yes

Longer answer: sort of...

You can combine in parallel multiple antennas (or antenna pieces) for different bands. The signal will go to all of them, and the "wrong" ones will have high SWR and thus (partially) bounce the signal back, and the "right" ones will absorb the signal and all the reflections.

The result is that while the right pieces are "chosen" they are also very slightly detuned by the group reaction (both internal and external). If the effect is small, you can ignore it or cover it up with a tuner. But it is also possible to retune everything (by modeling or iteration on the lengths) and get a perfect result.

You specifically ask about ground radials. The ground plane elements technically are radiating elements just like the vertical elements, and may actually contribute a significant amount of horizontal polarization to your signal. Also, they may have added loss resistance depending on closeness to physical ground. Otherwise, they basically behave the same as the rest of your elements.

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  • $\begingroup$ Thanks for this answer, and I agree with all you say about fan elements. My question though was about whether the ground plane radials would behave the same way as the radiating elements. $\endgroup$
    – quanglewangle
    May 20 at 15:58
  • $\begingroup$ decided to integrate this comment into the answer $\endgroup$
    – user10489
    May 20 at 17:31

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