This is just basic theory and applies to cable as well as RF(rooftop antenna, FM radio, etc): You need to boost closer to the input end of things. That is, if A where where a signal is received or comes into a house and B is where you will be watching it, then the amplification should be done as close to A is is practical. If your car antenna on the rear of the car, you need to run power back there and stick a signal amp inline right after the antenna. Otherwise all you're doing is amplifying sparkplug and any other noises present in the car.
Given, say, a 50 - 75' domestic run of coax, you'd want to amplify the signal no more than 20 feet in from the drop - 10 feet even! Then do your splitting right after the boost point. I personally made the mistake of sticking an FM amp between 40 feet of RG-59(was using my parents' unused TV antenna for FM years ago) and the back of the tuner. Didn't do a damn thing except eat electricity & drain my wallet.
Should've stuck the amp up in the attic, but had no outlets up there.
As for cable box installations, shouldn't need boosters or attenuators, unless you have only family cable with no boxes, just straight into the TVs. Case in point: My family cable service was so HOT I needed to throw -6dB attenuation in there - freebie from Cablevision!! All the mid-upper IRE whites blended together like a klieg light until I attenuated it. But when I got my 4250HD in the livingroom, off came that attenuator. And as mudshvel said, signal boosting will not help it if the station carried by the cable company decides to air shows at a color temperature of 4000K or 10000K!
Or if the interference is between the upfeed & the satellite, or between the sat. and the downlink(cable co.)
A cable box is more than just a channel switcher - it's a
sig.amp/attenuator/phase corrector/you-name-it, too, and should be able to do its job without any add ons.
