The hand-made antenna seems to function normally, but the bandwidth is narrow. I suspect this is due to insufficient surface area; replacing the wire with aluminum tubing or a thicker iron rod should improve performance. A better antenna will indeed have a relatively smooth and low resonant frequency line within its specified operating band... Professional antennas are designed with simulations, while hand-made ones require more experimentation. Another option would be to use a different antenna design to bring the resonant frequency as close to the desired frequency as possible.
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