Wavelength (m) = 300 / frequency in Mhz
On VHF the radio frequencies vary from 118-136 Mhz or so, therefore wavelength varies from 2.54 to 2.2 m.
VHF antennas are often 1/4 wave, so a 60 cm antenna is suitable, this can be helical or folded in a casing to minimise protrusion.
This stubby little VHF antenna can cope with this range of frequencies without any tuning in the transmitter.
On HF, say one frequency is 2.800 MHz and the backup 8.500 Mhz, wavelength now varies from 107 m to 35.3 m.
An good HF antenna is about half on the wavelength, so either 53 m or 18 m is required.
If you have a fixed HF antenna on your aircraft then some tuning of the antenna circuit is required to accommodate the large variations in wavelength due to the lower frequencies used.
The alternative is to use a trailing wire that varies in length with the change in frequency.
Not sure what kind of antenna you have, but when you press and wait for the tone that is the adjustment taking place.