How can I tune an antenna for receiving (VHF)?
An antenna can be as simple as a piece of wire (quarter wave monopole for instance or a half wave dipole for another example): -



The monopole (for instance) will receive any frequency but is inherently better at producing a stronger signal at one particular frequency and, as the name suggests, this frequency is at a quarter wavelength of the RF wave to be received.

So if trying to receive 300 MHz (wavelength 1m) you need a quarter wave monopole that is approximately 25 cm long. It will have a usable bandwidth (i.e. not require a retune) of probably 50 MHz (poor groundplane) to over 100 MHz (good groundplane). At the extremes the receive signal will be noticeably weaker but not necessarily unusable.

Think about commercial FM - it uses a monopole and tunes easily 88 to 108 MHz (20 MHz) with a centre frequency of 98 MHz.

This isn't true of a transmit antenna because the VSWR will be significantly worsened at extreme frequencies and power delivered to the antenna might be very small and may even damage the electronics driving the antenna.