Been working on optimizing my 2-meter EME setup and decided to run detailed gain measurements comparing a single M2 2M12 (12-element, 2.1 wavelength boom) against a stacked pair with proper phasing harness. The results were surprising. Single antenna: 14.1 dBi gain with clean pattern. Stacked pair: 17.2 dBi gain (exactly 3.1 dB improvement) but required precise 38-inch vertical spacing to avoid pattern distortion.

The catch? Stacking two or more identical Yagis can provide a 3 dB gain increase and a significant narrowing of the radiation pattern, but the key is proper spacing and phasing - the antennas must be spaced correctly and fed with a precisely constructed phasing harness to ensure the signals combine in-phase. Improper implementation actually degraded performance below the single antenna baseline.

Excellent data! I've been considering the same upgrade for moonbounce work. What did you use for the phasing harness construction? Also curious about the mechanical challenges at that boom length - wind loading must be significant with two long Yagis.

This confirms what I've seen in modeling software. These antennas are especially suitable for DX and contesting but the mechanical precision required for proper stacking often gets underestimated. Many hams jump straight to stacking without optimizing their single antenna first.

Great post! For us newer hams, could you explain what you mean by "pattern distortion"? I understand the gain numbers but not sure how to interpret the radiation pattern changes you mentioned.