i agree you can compensate for the problem with a low noise>3db, but my theory is to do it the best way to lowest s/n ratio. fix the problem instead of covring it up. i also realize the expense of good quad shield and connectors, so if you have to be on a budget than go the cheapest way to get what you need.
If you have a low noise amp you have the lowest signal to noise you can have (since we are yet to find a tuner with lower signal to noise.
If you have a 12 db amp and your line is say 6 db per hundred feet (RG6 at 600 MHz approx). So you have a signal that is 12 db stronger than it came out the antenna but you just added 3 db of noise to that signal with the amp. You can't add the gain and say well 12 db minus 3 db means we now have -51dbm signal. Actually we have less signal because the amp added noise. In a broad sense we now actually have a -63dbm signal.
So we go down 100 ft of RG6 in the example above and we used up 6 of the 12 db the amp provided, but we still have a -60dbm signal. But it's still more signal than would have had without the amp as then we would have had -66dbm.
So when we hit the tuner since the signal has already been through one stage of amplification, and have 6 db more voltage that was not lost, even if the first stage of the amp is say 8 db noise figure, we over ride any noise it adds with signal. So we have exactly the same signal to noise as we had coming out of the amp or a noise figure of 3 db. In other words we had 6 db to spare.
Had the cable been RG59, we would have had 2 db left over.
Until you reach the point where the gain of the amp is used up by the loss in the feedline system.
Ok, lets say you put 200 ft of RG6 on a 12 db amp. Then at 200 ft you run out of gain. At that point you just do have enough to maintain the lower noise figure the amp provided but it's cutting it close. If we add another 100 ft of cable for a total of 300 ft we now have 18 db loss in the cable but only boosted it by 12 db. So we now have a real loss of signal of -6db. Just like if there were 100 ft on the antenna without an amp. The amp in the receiver amplifies again and adds noise. The part I left out is the AGC circuit and dynamic range of the first stage in the receiver. But didn't want to extend this into that.
So if you have 12 db of gain, you can even use up to an old piece of RG 59 and get away with the same end result.
And the best things to do is throw away your crimpers and buy a cheap set of compression tools for coax. If you find a good one it will do 59 and 6. I have much fewer connections go bad without using any thing on the compression fitting once I am done.
