Harmonics are used in receivers, mostly in the oscillators. It is much easier to make a crystal at half the frequency, then use a tuned circuit after it with a frequency doubler.

I got shot down a very long time ago by a hospital radio working at roughly 146 MHz, because it was very powerful signal, and it mixed down to the IF frequency. The good ole days, the radio lock up with full up, and full aileron until it spiraled down to the parking lot. Kraft built tough equipment, but it couldn't reject 100 Watts from a couple of blocks away.