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Old 1-Sep-2014, 5:30 PM   #5
tripelo
Senior Member
 
Join Date: Jan 2010
Location: Dallas, TX
Posts: 171
Quote:
Originally Posted by timgr View Post
Simple question ... local big box hardware store, and looked at top rails and EMT...
There are different grades/strengths of fence top rail. Some are quite strong and have thicker walls that what you quote (0.054). Better grades are `0.080 inches thickness for the usual 1 & 3/8 " diameter, with yield strength of 50 to 60,000 PSI.

Stereocraig has a good point:

Quote:
EMT ... it was designed to bend
For the sizes you mention, the strengths might be close, mainly because the EMT diameter of 2 inches versus the top rail which is probably 1.315 inches. Strength goes up rapidly with increases in diameter.

It is good to try to minimize the mast diameter in the vicinity of a Yagi antenna (particularly UHF). The mast diameter can be an appreciable fraction of a wavelength and can interfere with the antenna pattern. This is partially why antennas such as 91xg have a cradle to help move the mast away from antenna elements.

For a given diameter, it can be difficult and costly to find stronger mast than a high grade top rail.

Some good info, Teleview:

Quote:
Originally Posted by teleview View Post
...TOP RAIL PIPE is galvanized steel , lasts a long time outside exposed to Weather Water.
EMT seems to be galvanized, but the galvanizing on the top rails that I have examined appears to be better. Guess top rails are are made to withstand outside exposure.

For a few reasons, many people like BroadwayJoe favor the top rail.

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Last edited by tripelo; 1-Sep-2014 at 6:58 PM. Reason: clarify
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