Would a good place to test SWR be on the interstate, like off in the
emergency lane.

That's really not a good place to do anything, except get killed.
A local Meijers or Wal-Mart parking lot would work nicely, anywhere that you
can get clear of metal for 1-2 wavelengths. But I doubt you'll see any
significant difference between that, and most home/on-street parking
situations.

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KC6ETE Dave's Engineering Page, www.dvanhorn.org
Microcontroller Consultant, specializing in Atmel AVR