Hi guys, does anyone know the best way to add sound to the O3 air unit? I looked pickup mics, but u need audio input in the vtx...

I seriously doubt it is possible or if it is whether it would even be worth it.  You would need a microphone, a preamp, then a digital audio converter, then you would have to patch that in to the feed somehow which would require a pretty significant hack of the device’s firmware.  It’s a bummer, I stumbled onto your post just now because I never realized the o3 did not have a mic onboard like the original air units

im not sure last version air unit has a built in microphone