Serious question about antennas and masts

So it goes like this. I’m covering Solid Signal’s chat lines and I get a person who has a question about his antenna. I got permission to post the question exactly as he said it:

I am wondering, since the signal loses strength as it goes through a cable, why do you say antennas need to be up on a high mast. Wouldn’t you just lose all the signal through the cable even if you get more from the antenna.

And you know, I had to stop and think about that. But really, the answer comes through the understanding of how much signal is gained and lost. See, on average, if you have a building or some trees between you and the tower, you are going to lose 5-6 dB of signal. That’s an average, and sometimes you will lose more and sometimes you will lose less. But that’s a good number to begin with. So if you put the antenna up on a mast you will get that 5-6dB back, and possibly even more because you’ll be up above other obstructions that aren’t as obvious to you.

Say in order to do this, you go up on a 15 foot mast. That means 15 feet more cable between the antenna and the TV. That implies a loss of only about 1dB. So even in this very abstract scenario, when the numbers are really just sort of plucked out of the air for example, you’re still netting out 4-5dB of signal because you put the antenna up higher. That is a significant difference and because this is all unamplified gain, in other words it’s signal that comes to you without any increase in noise, all that extra signal is working for you.

So this person really did have a point, but in the end putting the antenna up high still wins. It’s just that you do always have to figure in the loss due to cable when you’re figuring out what you’re going to be getting. In fact, addressing losses within cable is really the best reason to employ a preamplifier, which will strengthen the signal as it goes down the cable to compensate for long runs. All amplifiers do add some noise, making the signal a little less pristine, but it’s still a good idea if you’re going to be running more than 100′ or if you are going to split the signal to more than 4 sources.