Antenna modelling with EZNEC Pro/2 v7.0
All elements are in free space
Antenna boom or other metal structure for mast or mounting hardware is not in the in the calculation
The degradation seems to be on the highest frequency in this case 70 cm and stacking vertical has a bigger impact then horizontally with the antennas side by side.
The square stacking 2m with 70cm inside seems to surprise me with good result.
Ref ant. 2m YU7EF EF0213M Gain 16,1 dBi
Ref. ant 70cm YU7EF EF7027 Gain 19,50 dBi
First case is a 2m antenna close to 70 cm in vertical stacking.
Second case is 2m antenna close to 70 cm side by side
Third case 70m and 2m in square stacking
Ref ant. 2m YU7EF EF0213M stacking 4x4m Gain 21,96 dBi
Ref. ant 70cm YU7EF EF7027 stacking 2x2m Gain 25,32 dBi
*No loss was noticed on 2m besides the stacking loss for shorter stacking distance
Degradation of 2m at distance between 6m and 2m Yagi 1m=0.61dB 1.5m=0.31dB 2m=0.16dB 2.5m=0.02dB.
Note there is no degradations on 6m
Diagram of 2m:
Black=only 2m antenna
Blue=6 and 2m antenna with distance 1m
6m antenna at different heights above ground with Ground Gain tabs in Elevation
Black = height 2m above ground, angle 25 degrees
Blue = height 5 m above ground angle 15 degrees
Green = height 10 m above ground, angle 8 degrees
15 m above ground, angle 6 degrees
Optimal angle for ES jump 1400 km to 1600 km is about 6-4 degrees
20 m above ground, angle 4 degrees
At higher altitudes, the number of flaps increases and the elevation appears to level off at 2 degrees
I have done some more simulations on an antenna configuration with 6m to 70cm that I mounted in my mast. In the simulation, all antenna booms and metal parts in the antenna frame are included in the simulation.
The radiation patterns are affected by the metal construction and surrounding antennas but perhaps not as much as you might think. Degradation of gain is at most in 2m with about -0.5 db, 70cm and 6m have a couple of tenths of a degradation if compared to theoretical antennas set up in free space without any metal structure and antenna booms
Outer ring 13.54 dBi Max gain 13.4 dBi Degradation -0.14 dB due to influence from other antennas and mounting equipment
Current antennas at SM4GGC
Outer ring 21.62 dBi Max gain 21.07 dBi Degradation -0.56 dB due to influence from other antennas and mounting equipment
Outer ring 25.39 dBi Max gain 25.01 dBi Degradation -0.38 dB due to influence from other antennas and mounting equipment