I am new to ham radio and have been playing with a **RTL-SDR receiver** to which I have connected a vertical **1.5m monopole antenna**.

However, **I can receive transmissions belonging to the 40m band** (albeit with quite a lot of noise).

I have read in ham radio manuals that it is recommended to use a monopole of half the wavelength. But in this case, the length is much shorter.

**Why an antenna of that length is able to receive bigger waves**, is it because of the harmonics of the frequency or is it another physical phenomenon?

Thank you very much in advance.

—Fabian CD6FIQ

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