How is an analog TV transmitter different from a digital one?

NTSC analog was vestgial sideband making the most efficiency for power.

Transmitters for ATSC/DVB are near the same but have to run 100% .

Means transmit power has to be limited to about 72% power.

For the most part, the hardware is quite similar.

The transmitter itself isn't much dfferent. 

What is significantly different is the modulation applied to it. 

Digital signals consist of precisely timed on-off pulses (ones and zeros), 

whereas an analog signal consists of a continuously varying waveform. 

In an analog TV signal, there are several waveforms that have to be precisely timed

so that a TV can use them to construct a decent picture on its screen. 

In NTSC, the ultimate reference is the horizontal sync pulse at 15,734 Hz. 

The vertical sync pulse is 29.97 Hz, timed so that it corresponds 

in the right way to the horizontal pulse. 

The one that needs to be most precise in frequency, though, is the colour burst. 

It has to be Exactly 3.579545 MHz, or 3,579,545 Hz,  

in order to allow correct colour reproduction. 

Still, as precise as it must be in practice, it is usually Called "3.58 MHz"  

to avoid having to include all the digits when referring to it. 

An analog TV signal consists of a carrier amplitude modulated but the video.  The audio is FM modulated on a 4.5 MHz sub-carrier and that also AM modulates the main carrier.

In a digital system, everything is digitally encoded and the digital data stream amplitude modulates the carrier.