Where to buy 15 ft 3.5" OD pole?

It wont be 12' in the air. At least 4' should be in the ground. Then he has to reach to the center of a 10' dish. That sucks up about 9' already. There could be another reason to lift it another couple of feet to clear a rock or something.

Done right, it will not be a disaster.

I used to use my 10' dish as a UHF antenna, with a bowtie in place of the LNA. Got extremely good distance reception. But my question of why so high still hasn't been answered. This is a repair group. You know that whatever gets put up will need some tinkering. So why put it up any higher than to clear the ground? True, there may be horses, kids, whatever that need to have it above them. That's fine. But why a 10' instead of 18", and why so high? Inquiring minds want to know.

For me, it would be 3' of snow.

How's he going to point it at the satellite when it is laying on the ground? The flattest elevation angle in the mid-latitudes is 49 degrees for a bird that's at the same longitude in the Clarke belt as the ground location, and gets steeper toward either end of the arc. The lower lip of the dish must clear the ground at minimum beam elevation (dish 90 degrees to the Earth's surface) in order to cover the entire arc.

That means the mount point must be more than 5 feet above ground level for a 10 foot dish. But that's not enough if he wants to maintain a reasonable antenna noise temperature. To do that, the major dish sidelobes must clear all terrestrial obstructions.

In flat terrain without a raised horizon, and assuming a typical 2 degree half angle for the first major dish sidelobe, that means the bottom edge of the dish needs to be at least 3 feet above ground level. For rougher terrain, or locations where there are far field obstructions (buildings, trees, etc) out toward the horizon, the dish will need to be higher.

So *at minimum* he needs a mount pole that sticks 8 feet out of the ground. A 12 foot pole lets him do that, with 4 feet set in concrete in the ground to resist the overturning moment.

That's why he needs a heavy pole. 3.5 inch diameter pipe is actually a bit on the light side for this size dish. I have my "small" 12 foot dish mounted on 6 inch pipe. The larger one (a 10m Scientific Atlanta dish) is mounted on a 24 inch diameter heavy wall steel pedestal designed for the dish.

The overturning moment on medium to large size dishes is very high in even moderate winds. My big dish needs a mount capable of withstanding over 250,000 foot-pounds in a 50 MPH wind. You need a well engineered reinforced concrete base to withstand the forces, and a heavy enough pole to avoid bending under the load.

BTW, as a source of pipe for the pole, I'm using 6 inch oilfield well casing, aquired as free scrap from a friend in the business, for my small dish. The pedestal mount for the larger dish was custom fabricated by Scientific Atlanta, and came with the dish. There's

Gary

Take a drive down to Annapolis and check out the rigging and boat yards, particularly over in Eastport along both sides of Back Creek. Sounds like you could use a piece of somebody's cast-off aluminum mast section. There is a fair bit of it lying around in the yards out there -- ask around, you'll probably find somebody to sell you a length for not too much money, since it wouldn't be much good for anything else.

Regards,

Bob

On Sun, 17 Oct 2004 20:50:34 -0400, Gary Coffman vaguely proposed a theory ......and in reply I say!:

remove ns from my header address to reply via email

OOI, and PMFJI

Is there any reason not to use a pyramid tower made up of smaller poles, to give a nice spread base? Most windage is overcome this way.

That's true, but it's also true of pipe schedule from 5S through XXS. Pipe outside diameter doesn't change, wall thickness (and inside diameter) does. For a sturdier mount, one could go to a higher schedule, assuming cost was not an issue.

Harold

Maybe you can tell why, nowadays, a 10' dish for TVRO?

Lots of suggestions and sidetracks (interestin) in this thread. To reply to 'where to find it?' - go to any welding shop or business using iron in construction (farm equipment & fertilizer in this area). They will have stock sizes in 20 ft lengths. May even cut to size at no cost. I doubt if you will find it any cheaper anywhere else except a scrap yard. I suspect plumbing shops would be higher.

Harry K

even with a fairly large size pole, you will still get quite a bit of wind sway with a dish on the top. I would instead make a tripod of much smaller tubing (1 sch 40, maybe). The resulting structure will be much more rigid.

bill

At the time I responded, he only said he was mounting a satellite dish, without mentioning the size of it. The dish I was picturing was the small oval type supplied for services such as DirecTV and such.

Never assume anything from a first post. It usually takes 3 or more follow-up posts from the OP before you can assume anything. By the 5th or 6th follow-up, you may actually have enough information to offer a suggestion/solution/link. :-)

The best place would be a metal supply business. I break my spinnaker pole too often, and I can pick up a replacement aluminum pole and reinstall the fittings far cheaper than by buying at a chandler.

I would, however, offer an alternative suggesti> I'm putting up a satellite dish and I need a 12' 3.5" OD pole, would

if you're breaking a spin pole often, you're either doing something wrong or need a bigger/thicker section. try a carbon fiber tube which actually aren't that hard to make.

I thought he asked a perfectly good question, it was the responses that were all over the place! FWIW: All big dishes use 3 inch schedule 40 pipe (at least those from 6 foot to 12 foot). I just had to buy some myself, and it is about $10 a foot, from a metal supply place.

Prices must be different where you are. I just called Curtis Steel in Las Vegas. I have an account there, but did not mention this. The price I got over the phone was $116 for a 21 foot piece. Schedule 40 pipe comes in 21 foot sections. That works out to a price of $5.52 per foot.

I really believe that a piece of this pipe, or a piece of adequate I beam could be had at a scrap yard for a lot less than the $116 price I found, or the $210 price the other poster quoted. Schedule 40 pipe is tough stuff, and unless it is totally corroded, a used piece will do as good as new. Paint will hide a lot of stuff.

If you paid $10 per foot, you might want to check with your supplier or shop around a bit more.

Steve

Ability to receive C-band. (Dish and DirecTV are Ku-band)

I was buying a "less than 21 foot" piece, so I'd expect to pay more per foot than for a full piece. Also, I didn't shop around, I just went to a place that I expected to have it and paid retail. FWIW: The polar mounts for these dishes are designed to fit around 3 inch pipe, and it would be a PIA to make them work with something else. Not impossible or even difficult, but a PIA never the less.