With a Hand Held Radio - the person holding the transceiver is the ground plane. Because the human body is comprised mainly of water, it acts like the missing half of the antenna.
Radio waves in front of the person is radiated, radio waves behind the person is blocked to a small extent because of the water in the persons body.
This is the reason why Rabbit Ears antenna's do not work in concrete apartment buildings with people moving around the room.

The person who is walking around blocks some of the reception - especially in the higher frequency ranges because anything one or more wavelengths in size can and will block a signal.

I'm surprised that no one caugth the foopaugh that the origional answer giver had made when he described how a antenna works.

The reflector has to be a certain size for a certain wavelength and there is only one driven element.
The other elements - also known as directors - gathers the signal and directs them backwards in the array towards the reflector.
Each director gathers the same amount of signal as a dipole and each director adds gain to the antenna at the expense of beam width.

The only way to increase gain is to give up something somewhere else.

If you stack two antenna's one above the other - one wavelength apart - and build phasing lines, each antenna will only agument the other by a gain factor of 2.85 - reguardless of how much gain the origional antenna had.

If you stack two beam antenna's, one or more wavelengths apart - the apature becomes smaller - hence if you put enough of them together, it is as if you were trying to look through a straw while driving an automobile.

The beam width becomes very narrow, while increasing forward gain to the point of infany.

With a UHF signal - eventually when it runs out of things to bounce off of - it just travels in a straight line - out into space, never to be recovered again.

I think the OP was asking about receiving antenna's and not transmitting antenna's.

A receiving antenna - works best when it is cut to one individual frequency, but those antenna's tends to be more expensive, not less, because they have to be purpose built. The size and spacing has to be more exact to get the results the buyer is looking for.

While a VHF antenna, with the use of phasing lines, a person can make a very broadbanded antenna and it will still work up to the length of the longest combined element.
When the elements are too long, the antenna can look back through the array and can match the wavelength to the elements in the array...