Why Radio VOX is unreliable on a bike.
Many radios come with Voice Operated Transmit (VOX). I am often asked if VOX could be used on a bike to do away with pressing buttons.
The short answer is NO!, not without help.
VOX relies on detecting the loudness of your voice to trigger the radio to transmit. The radio cannot tell what noises are voice and what noise are..well... 'noise'. Wind being the main noise source.
Where your Mic resides inside your helmet noise levels vary hugely depending on whether you are sat at a red light or going 70 into a head wind. The VOX circuit in all current radios is just not smart enough to cope with this huge variation of noise. This will then cause the VOX to false trigger the radio to transmit.
VOX that Works
Reports are that Autocom VOX systems are pretty good. Apparently they dynamically change the VOX trigger level depending on background noise. I have no experience of this so cannot confirm if this is the case.
A simple and low cost alternative to the Autocom is our VOX-MC which enables you to manually adjust the VOX level as you ride.
The only really reliable way to use a two-way radio on a bike is the have a handlebar mounted transmit button or a suitable external VOX system. That way the radio only transmits when you want it to.