Safety concerning ERP of transmitter

[davenn]

But we have to assume the OP is legit or we shouldn't be having this conversation.

probably a really bad assumption
don't think I have ever seen one of these styles of posts where the OP was operating in a legit way

 

[GrahamN-UK]

The cables used are RG59.

As well as the high losses mentioned by davenn, RG-59 cable has a characteristic impedance of 75 ohms whilst the antenna you proposed is 50 ohm (from its data sheet). You need to use a low-loss cable with the same impedance as your chosen antenna to reduce matching losses and ghosting on analogue video (at least on long feeder runs).

Antennas used for broadcast reception tend to be 75 ohm whilst antennas used for transmit/receive systems are usually 50 ohm. You should check the specification for the antennas you choose then get matching cable and connectors.