Is a lot of signal lost using a 20' coaxial lead?

[idiotbox]

I need to connect several old TV's to RF modulators, which will then be connected to various digital converters to connect to my laptop. My laptop/control station will be about 15-20 feet away from the TV's, so I need to make one of the paths a long one. Is it okay if I made the coaxial cable long or will a lot of signal be lost? Would it better to make the RCA composite cable long instead? Or further down the chain, such as the VGA cable or even the USB cable? Thanks in advance!