In article ,
Al Lorona wrote:

I have always heard that "13 feet, 6 inches" is a standard for the maximum
height of an antenna mounted on a vehicle.

However, I cannot find a credible source on the web verifying this "fact".
NHTSA, DOT, don't seem to have such an antenna regulation on their
respective web sites. I am not the most skillful user of Google, but my
searches have sure not turned up a reference to this magic number on any
authoritative site. Perhaps there is no national standard, only 50 separate
state standards, and the state with the lowest height limit would then
become the 'national standard'??

I don't think there's a maximum antenna height, per se. However,
there are some standards for the minimum heights of bridges and other
overpasses.

Take a look at

http://wwwcf.fhwa.dot.gov/legsregs/d...pg/0625sup.htm

Specifically, section 7A specifies that sections of the Interstate in
rural areas must have a clear height of not less than 16 feet, while
some Interstate routes in urban areas can be as low as 14 feet.

I believe that the "13-and-a-fraction foot" height is intended to
ensure that the vehicle can pass along all conforming Interstate
routes without hitting anything... it's a comfortable margin below the
14-foot urban minimum. I've heard "13 feet 9 inches" as well as the
"13 feet 6 inches" figure you mention.

There are some exceptions: Interstate overpasses below the specified
minima. See

http://www.aitaonline.com/Info/Low Clearances.html

for lists.

--
Dave Platt AE6EO
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