A There are common two rules of thumb:
- The higher antenna should be separated from the antenna immediately below it by a distance equal to at least a half wavelength at the higher antenna’s operating frequency (see Figure 1), or…
- The higher antenna should be separated from the antenna immediately below it by a distance equal to at least half the boom length of the higher-frequency antenna.
Using the second rule, for example, you can place your 6- meter antenna about half its boom length above the tribander. Then place the 2-meter antenna about half its boom length above the 6-meter antenna.
For some installations these rules of thumb will yield separa tions that are impractical. If this is the case, simply install the antennas as far apart as possible.
Figure 1—To minimize interaction between stacked Yagis on the same tower, a distance equal to a half wavelength at the higher antenna’s operating frequency should separate the higher antenna from the antenna immediately below it. Alternatively, a distance equal to at least half of the higher frequency antenna’s total boom length should separate it from the antenna immediately below.
From QST July 1999
