[HCARC] DEE-BEE's, Amps and Antennas

[Gary and Arlene Johnson]

I think there is a conspiracy - IF GARY J doesn't ask questions on the Reflector, no one else does.

Todays question is about amplifiers (no I am not getting one anytime soon) and Gain Antennas (I have to have something on the tower).
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My understanding of Dee-Bee's is that theoretically if I double the power then I gain 3 Dee-Bees.  So from 100 watts to 200 watts gives me 3 Dee'Bee's.  200 to 400 gives me another 3 Dee-Bees, 400 to 800 gives me another 3 Dee-Bees and 800 watts to 1500(ish) gives me another 3 Dee-Bees.  It seem intuitive that from 100 to 5-600 gives you the most bang for the watt, and from 500 to 1500 more expense, for less gain per unit input.

If I take the 7 gained Dee-Bee's for a 500 watt amp and run them into a gain antenna (say a Cushcraft A4S which the specs say gives me a gain of 8.9 Dee-Bees front to back are they then additive (i.e. 7 plus 8.9)???  Therefore a 500 watt amp driving a gain antenna does better than a 1500 watt amp driving a non-gain antenna.

It appears that good gain antennas are at least as inexpensive as amplifiers and maybe more so.  It also brings to light the losing of Dee-Bees in transmission lines and the like is nuts - why buy amps to gain them and then turn around and lose them again.

Has my meager math ability made any major mistakes???

Gary J
N5BAA
HCARC Secretary 2013