How can a wireless radio device be modified to transmit and receive a camera signal?

 

The short answer is "no".

The long answer is, "video signals can be transmitted wirelessly but the bandwidth required is much wider than a voice channel used by ordinary portable radios, so it requires a purpose built system operating on frequencies that permit the transmission of video".

 

I suppose, technically, the response should be 'it depends' as an FM radio at 100MHz could, in theory, carry a medium resolution, low-frame rate CCTV signal (B&W VGA, 10fps

So:
What radio?
What camera?

 

I suppose, technically, the response should be 'it depends' as an FM radio at 100MHz could, in theory, carry a medium resolution, low-frame rate CCTV signal (B&W VGA, 10fps

So:
What radio?
What camera?

There are regulatory components to this question which should be considered as well. My answer integrated those given the form of the question.

 

Agreed. Besides the technical difficulties, there are regulatory restrictions that prohibit the transmission of encoded signals over channels intended for voice.

 

The 5.8 GHz FPV range can transmit down the street and extended range several miles using ham technology, popular for drones.
The video shows an RC plane fix on a balcony. The test shows how he tested the video range and RC signal. The 200mW smaller FPV
was given favorable review.

A Push to Talk hand held radio is for talk and FPV is for video. A composite of voice and video is one way transmission and
Duplex is seen on limeSDR 20mW has the BW but needs an amplifier. The raspberry pie shown is clever, to get range the unit needs a power amplifier, however your cell phone does it all.