Sorry Gary. I got distracted by the troll. How about marine radar (taken from another thread)?
It sounds like a typical, off-the-shelf military radar has a range of about 25 nautical miles (although some have much further range). I believe 25 nautical miles translates to 46.3 km.
https://www.quora.com/What-is-the-range-of-an-average-marine-radar-on-US-Navy-ships?share=1
We all know that radars only travel in straight lines. Presuming the radar is mounted 10 m above the water (I think this is conservative, as lots of boats would be shorter), and the boat it is detecting is 10 m above the water, the maximum distance the radar could detect another boat on a ball-Earth is 24.79 km.
To confirm, just enter the heights of the observer and object in the calculation page attached.
https://rechneronline.de/sehwinkel/distance-horizon.php
So, ball-Earth theory predicts a maximum radar range for the most powerful radar of 24.79 km, due to the curvature of Earth, but a standard radar (probably mounted much lower) can detect up to 46.3 km. Note also that more powerful radar can purportedly achieve much greater range.
How does this work on ball-Earth? Either radar travels in curves the same way ball-Earth curves (neither measured nor observed), or ball-Earth theory is false.