John,
As you can see from the posts there is no 'one' answer
for that question. Just depends on exactly what you are
interested in doing.
The 'average' antenna farm is squeezed into an average
city lot, with variable compromises. The 'optimum' antenna
farm fits in an area something the size of Kansas (with over-
lap in the surrounding states). Again, with variable
compromises.
The 'typical' answer is whatever area you happen to have,
with variable compromises...
'Doc