Fence

Post spacing should not exceed 16 feet. It does not matter the type of wire are the post type. Post spacing should not exceed 16 feet.  And 12' is better. 

A welded pipe H with a diagonal is far superior to any wooden brace.

A diagonal kicker should be installed on any turn greater than 15 degrees.

Spacing on braces is only limited by how well you build them and how far you can stretch the wire. Up to about half a mile. 

Stu I would have to say that is homemade.  I certainly wouldn't know what to call it or where to buy one. But it shouldn't take all of 15 minutes to make one. 

Good luck.