Does the length of coax decrease performance in scanning as much as
when you are transmitting?

I can put an antenna in my attic where I will only have about 5 feet of
coax. (My scanner is upstairs) I could mount an outside antenna on top
of my tv tower at about 30 feet, but would need to run about 50 feet of
coax. The total elevation if it was in my attic would be 20 feet or so.
(But I do have alot of insulation that might block the signal).