Direct AV injection

[kf4rca]

A CATV modulator generally puts out about 60 db. Thats because some loss (12 db or so) occurs in the combining process with other channels that are also used. Generally the line level leaving the headend should be about 42 db so that the output from the first tap (say a 32 tap) is about 10 db.
A TV normally likes to see 0 to 10 db in to the tuner. Yes you can transmit from a modulator for a short distance. 78 db is 1 watt. 75 db is 1/2 watt.
Ideally you need a high gain antenna to put a decent signal around the neighborhood. But a yagi is directional. For a non directional antenna a super turnstile would be best.