I've never thought about checking the loss in RG-6. If it worked I figured that it was okay. But after hearing that a 3 foot piece had a 1.3 dB loss, I'm going to be checking all of my cables from here on out. I have no way to measure except to compare one cable to another cable, but at least I'll be able to see any drastic losses.
I guess my 4228 pointed at Walnut Grove works so well because I have just one 65 foot piece of quad shielded RG-6 between the antenna and the antenna switch selector box. The other antenna set up, the 4228/Y7-13 combo, has short coax pieces connecting the antennas to the coupler then a 100 foot run of RG-6 to a distribution amp then four runs of various lengths to the TV sets. I get nowhere near as good results with that set up. I suspected that it was antenna location, but it could be bad coax, connectors, etc. causing loss. One bad cable could mess up the whole shibang.