Asked the question as I had to totally retune my 11 ele 2M yagi after it was positioned about 7 ft above the TA-33.
Thanks for both suggestions
That I can understand given the big difference in antenna frequency coverage between the two antennas. When I mounted my 7 element 6 meter beam at roughly 4 feet above the tri-bander, the lowest resonant point of the 6 meter beam shifted about 50 KHz (can't remember if it was up or down). When I mounted it roughly 8 or 9 feet above the tri-bander, the lowest resonant point shifted back to the original frequency.
Obviously, there might be some interaction given the closeness of your two antennas, but I would expect the 17 meter dipole to probably be more affected (i.e. resonant point) then the tri-bander.