forget.... I'm astounded at your assurance!!! If he tried a quarter-wave piece of wire it may produce results but if you do not realise that a random length of wire stuffed in the back of any VHF radio will not work as well as a properly cut antenna then your 40 year in radio/avionics leave something to be desired!! You surely realise that scanners are like barn doors - no filtering or tuned inputs. Shove a long bit of wire, without an ATU, in his scanner and our friend will more than likely get radio 4 on the airband. However, if he uses a half-wave dipole not only will reception be enhanced, but it will go someway to filtering out out-of-band signals.
HD (30 years radio amateur, cycling proficiency badge, film projectionist, etc, etc)