Antenna tower side arm mount heavy duty cross member. 1-3/8 pipe with cross member.
Very heavy duty made for large Antennas. Many different ways to mount to A tower leg. I show with muffler clamps.
Auto Zone has many to pick from. You can use hose clamps, I wood use at least 6. If you need a different mount made let me know.
I have about 10 on my store page.