tmodem, I would go with at least 1.5" EMT in your situation. For the lengths you're using the 5' pole atop the rotor will not cause much vibration stress on the rotor with a thicker EMT pole than what you've got. Those RCA chimney brackets will hold just fine as long as they're tightened correctly. The chimney itself would probably fail before those would, and I've seen plenty of them still attached to chimneys after 30 years!

1.5" conduit will not fit in the chimney mount brackets (U-bolts). I always use 1-1/4 condiut.
The RCA chimney mount kit comes with 2 straps. If I'm going that height, I recommend 2 kits, 4 straps makes it pretty solid with 1-1/4 pipe.

It's the 12" Channel Master wall mount stand-off bracket.

I've seen some people (http://www.digitalhome.ca/forum/showpost.php?p=964114&postcount=408) in the pimp my gear thread use the 3 point bracket at the bottom... but since the bracket doesn't come with any guidelines/instructions, I just used it on the top. I'm not sure which one is correct or better.

As DdDave says, the third leg is for vertical support. I don't think it will provide any significant lateral support. However, since the leg is coming off at an angle, it will translate some of the vertical forces into lateral forces and thus (depending on the wind direction) could actually increase the load on the other two legs. For this reason, I recommend using it as the bottom bracket where the lateral forces are lower to begin with.

If, as shown in the picture, the pole continues down to the ground (or something else that it can rest on for vertical support), the vertical forces on this leg won't be as high and this won't be as important.

I hope this helps.

The RCA chimney mount kit comes with 2 straps. If I'm going that height, I recommend 2 kits, 4 straps makes it pretty solid with 1-1/4 pipe.

As I said earlier in this thread, the top strap (or bracket) acts as a fulcrum and thus takes the most load. Adding extra straps will not decrease the load on it.

Thanks roger1818 and DdDave, it does help.

I guess they just assumed DIYers would know how to install these things :)

Moving the bracket would be quite a chore. Do you think adding a 2nd 3-point bracket at the very bottom would help ease the load?

Like so?


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Do you think adding a 2nd 3-point bracket at the very bottom would help ease the load?

Increasing the spacing between the top and bottom bracket (by adding another bracket that is even lower) will definitely reduce the load. If you do use a second 3 point bracket, you could loosen the top vertical support slightly afterwords to ensure the vertical load is taken by the lower bracket.

Once again, this forum provides a ton of excellent information!! Thanks for the advice everyone!!

I went up on the roof today and shortened the antenna pole by a foot and took all the plastic off the 4228. A lot more stable now. As per Stampeder, I can use 1.5 for the antenna but as Tom says, 1.25 is all I can use for the mast. I will make adjustments this weekend.

2 Quick questions!

How tight can you make those chimney straps?? It seems like I can turn those nuts forever. It's tight now and the brackets don't move. I just don't want to over tighten.

In a wind storm does anyone angle their 4228 so that the wind hits the edge of the antenna? Will it make a difference?

I can use 1.5 for the antenna but as Tom says, 1.25 is all I can use for the mast. I will make adjustments this weekend.

It's strange the way they refer to the conduit that is 1.5" OD as 1.25", when neither the ID nor the OD is 1.25". I'm sure there is some reason that made sense to someone at some point in time, but I'm sure it caused more than a few people to end up with the wrong conduit when they tried to install their antenna.

Anyway, upsizing from 1" (actual OD 1.25") to 1.25" (actual OD 1.5") will make a huge improvement to the stiffness. The moment of inertia is what determines the stiffness of the pipe, and as the radius gets bigger the moment of inertia gets really large really quick (it's a fouth order increase). In this particular case, increasing the diameter by 20% will almost double the stiffness.

In a wind storm does anyone angle their 4228 so that the wind hits the edge of the antenna? Will it make a difference?

If you knew the direction of the wind would stay constant it would help reduce the wind load, but since the wind is going to be changing directions all the time it won't be worth the effort.

I live in the Brampton Ontario area.

Does anyone know where you can get a ten foot pole for the tripod setup. I see a lot of shorter ones.

I don't know whether I can get the signal from both Buffalo and Toronto on one antennna, so I figure I need the longer pole if I have to mount two antennas.

Has anyone success fully setup an antenna system and what did you use.

Thanks
Harold

10' x 1-1/4" EMT conduit is 18.98 in the electrical section at every Home Depot store.

I use 1.5" OD aluminum pipe (1/8" wall thickness) which I got at Metal Supermarkets in the Dixie/Courtney Park area (I can't think of the exact street offhand).

The shop will cut it to whatever length you want, it will never rust and it's very lightweight. Only downside is the cost which is about double that of EMT conduit.

Thanks for the response. I was looking at Electrical conduit last night at Home Depot and thought that it should work okay.

I can see that the alminum would be lighter.

Thanks again
Harold

I don't recommend aluminum poles. Although it has a better mass to tensile strength ratio than steel, weight is not a big issue for poles and the same diameter of pipe isn't as strong. Aluminum is also softer. I don't think its shear strength is as good either. You also have to be careful to make sure nothing made of steel touches it or else the aluminum will accelerate the rusting of the steel. Besides, a galvanized steel pole is not likely to rust during the lifetime of the antenna.

Hi, I live northwest of Dixie and Queen in Brampton and I am getting ready to instal my 4221 on an eave mount at the peak of my house. My roof does not have a very steep pitch so there is only 12 inches between the 2 brackets below the roof. How high can the mast be above the roof?

Any suggestions on which direction to point it?

Thanks

Pauliachi, 12" separation between the mounts is not very large. You may want to re-think your mounting and come up with something more stable. I think that most people using wall mounting brackets space them at about 3' and then use a 10' mast, and that's mounting into brick. It may be a bit over-designed, but it works. With your 12" spacing I would not want to put up any more than a 3' mast above the top bracket, and that's assuming they are well anchored. I have no calculations to back this up, just a gut feeling.

Any suggestions on which direction to point it?

Check out tvfool.com to find out which direction the transmitters are located.

Pauliachi: Have you considered a tripod roof mount? I agree with DdDave that 12" isn't enough separation.

I think the rule of thumb for spacing is that 20-30% of the mast should be between the brackets. So with 1' separation, you would only safely support a 4'-5' mast.

I don't recommend aluminum poles. Although it has a better mass to tensile strength ratio than steel, weight is not a big issue for poles and the same diameter of pipe isn't as strong. Aluminum is also softer. I don't think its shear strength is as good either. You also have to be careful to make sure nothing made of steel touches it or else the aluminum will accelerate the rusting of the steel. Besides, a galvanized steel pole is not likely to rust during the lifetime of the antenna.
I've used an aluminum mast for my amateur radio antennas which are considerably larger than anything OTA and have had zero strength problems since they went up in 2002.

Aluminum tubing of the same gauge as steel is definitely not as strong. But the stuff I use has a wall thickness of 1/8". It is very stout stuff.

And the cut ends of a galvanized pipe will rust in no time at all unless they've been galvanized as well.

weight is not a big issue for poles

actually that is exactly why I DID use aluminum masting. I used it for a 30 ft telescoping antenna mast.

At 3 times the weight (density) of aluminum, steel is very heavy. This is significant if you are mounting and dismounting yourself often, especially on longer lengths.

As for strength, its just as good as steel if properly braced, as you would with steel.

The dissimilarity of metals is a disadvantage no matter

And the cut ends of a galvanized pipe will rust in no time at all unless they've been galvanized as well.

It depends. If it is just electroplated with zinc, then that could happen as the layer of zinc is very thin, but if it is hot dipped galvanized, the galvanic reaction of the zinc should protect the cut ends. It isn't like paint that needs to cover the metal completely and any exposed parts will rust.