6.5 for UHF and about 19.5 inches for an OK performing dual band VHF/UHF radio. Normally with a handheld radio the counterpoise (ground) is your own body as you are holding the HT. This is because ...
Many pilots carry a handheld radio with them in their aircraft as a backup in the event the primary installed com radio fails in flight. When the pilot is using an automatic noise reduction ...