Setting aside the fact that RF distribution operates at 50
Ohm, and
Composite video operates at 75
Ohm, this is poor practice for several reasons. First,
composite video has a different
line voltage requirement than antenna distribution. Assuming your video distribution is applying a fixed
gain to all outputs, using video distribution equipment will end up applying too much additional
voltage to the outputs and you risk pumping so much
gain that noise floor becomes an issue at best, or damage to the front-end of your Receivers at worst. Every time you split an antenna signal, you halve the
power -- the outputs of the splitter are taking into account the average
line voltage and applying fixed
gain to make up for this loss of
power. +3dB applied to 2V is NOT the same as +3dB applied to 2mV!
This
power situation is why you can passively split a
composite video signal one or two times without issue -- your receiving device can compensate for halving the
voltage because it still has enough data to work with before the signal falls into the noise floor. In RF land, you don't have that much
power to start with, so you need to actively split (though there are times where you can passively split once, but you still need a
passive splitter that has some isolation circuitry - I keep a Mini
Circuit ZAPD-1+
BNC in my toolbag for those rare times).
Second,
composite video has different frequency requirements than most
UHF RF requirements. You buy an antenna splitter that best matches the frequency requirements of the job, in this case it is
UHF from 470-952. There are filters on the antenna inputs to make sure the
unit filters out all outside noise above and below the desired frequency range.
Composite video's
chroma carrier is around 4.5mHz, and you add bandwidth as you add resolution, which can get quite high depending on several variables (ex: Color vs b&w). Regardless, 4.5mhz is well below the 470mHz of the
UHF range.
Just because you can do it, or have tried to do it, doesn't mean you should do it.
