"Tam/WB2TT" wrote

You know that can't be right, because combining two antennas
gives 3 db gain.
_____________

The vector sum of the EM fields at every point in free space from identical
radiators fed by the same source depends in part on their relative physical
orientations, and their separation in wavelengths (see Kraus' ANTENNAS, 3rd
edition, chapters 5 and 6).

If all radiators in an array generate identical fields relative to each
other, then the peak directivity of an array of two radiators exceeds 3 dB
for radiator spacings of about 0.75 to 1.2 wavelengths (max of about 3.3
dB).

If they are spaced 1/2-wave apart then the peak directivity drops to about
1.9 dB, and at 1/4-wave separation it drops to about 0.5 dB (see Johnson &
Jasik ANTENNA ENGINEERING HANDBOOK, 2nd edition, Figure 3-4).

RF