20m antenna at T93M is 4over 4 Yagi at 26m/13m above the ground. Bottom antenna is fixed to USA. Antennas are 4 element Yagi's, home made, designed by me using EZNEC modeling software. Boom length is 24' (7.4m) and antennas utilize the second driver as close spaced director to achieve the uniform VSWR across the whole 20m band.
Antennas spacing is only 13m (0.61wl). It came to me as surprise that this spacing is optimal for these antennas at my particular antenna position. Actually tower is positioned at the edge of the small hill sloping toward the NW (USA). After irritations in HFTA software by N6BV I came to believe that this separation will best serve my needs of TOA (Take Of Angles) for contest station.
HFTA software is great tool to evaluate antenna location as well as tool to determine the height of the antenna over the ground for maximum performance.
HFTA (formerly YT-Yagi terrain) software is available only via purchase of ARRL antenna handbook.