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-   -   EMT vs. top rail (http://forum.tvfool.com/showthread.php?t=14807)

timgr 31-Aug-2014 7:17 PM

EMT vs. top rail
 
Simple question - usual recommendation for antenna mast is the top rail for chain link fence. I was in my local big box hardware store, and looked at top rails and EMT. The price is about the same for both, and both are 10' long. You can buy 2" diam 10' long stick of EMT for about $3 more than the top rail, which I would think would be a superior mast. 2" EMT is supposedly 65 thou (ca 15 ga) while the top rail is 17 ga (54 thou).

Stereocraig 31-Aug-2014 8:03 PM

Quote:

Originally Posted by timgr (Post 46068)
Simple question - usual recommendation for antenna mast is the top rail for chain link fence. I was in my local big box hardware store, and looked at top rails and EMT. The price is about the same for both, and both are 10' long. You can buy 2" diam 10' long stick of EMT for about $3 more than the top rail, which I would think would be a superior mast. 2" EMT is supposedly 65 thou (ca 15 ga) while the top rail is 17 ga (54 thou).


Not sure if there is any truth to it, or if I was just expected to believe it, because he was my foreman =D

Back when I was building scaffolding, I needed a temp handrail and found a piece of 2" EMT.
The foreman told me not to use it, because it was designed to bend.

If nothing else, you have my permission to add this to your urban legend repertoire =D

teleview 31-Aug-2014 10:52 PM

+=>

The , 10 foot 6 inch length , 1 and 3/8 inch diameter , TOP RAIL , chain link fence , PIPE.

Has a , Swaged End , so the pipes can be put together.

The 10 foot 6 inch length can be cut to shorter length , and has the Swaged End makes it easier to add a pipe later to increase the length.

The Swaged End can be pointed up toward the sky or down toward the ground , makes it easier to add a pipe to make the over all pipe length longer.

The Swaged End is smaller , For installing antennas that have smaller clamp.

TOP RAIL PIPE is galvanized steel , lasts a long time outside exposed to Weather Water.

BroadwayJoe 1-Sep-2014 4:41 PM

I am using top rail for mine. I have an eave mount bracket, and my antenna sits about 10' high. I added a grounding block, and have everything grounded to my homes electrical ground. Been up for over a year now. No complaints.

tripelo 1-Sep-2014 5:30 PM

Quote:

Originally Posted by timgr (Post 46068)
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 (Post 46076)
...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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