Rollie wrote:
.. . .I've always used the (6db per
S unit) as a general rule-of-thumb.

Which is fine if you don't mind possibly being off by a factor of 50 or
more, mistaking the gain of a 3 element beam for the gain of a 150
element one. Or you might only be off by a factor of 10, thinking the 3
element beam only has the gain of a 30 element beam. Shucks, what's a
few dB anyway.

Roy Lewallen, W7EL