(to Western Hemisphere,Eastern Hemisphere,Footprints by Dish Size) Installation Discussion Ground Pole/Pad Mount and Wind Loading (to dish size list or tuning page)
GROUND POLE: The major item here in setting the ground pole is plumb, plumb, plumb - make sure the pole is perfectly vertical; though first thing, check for obstacles in your viewing path and choose appropriate pole for your dish diameter (see wind loading). Rule of thumb on minimum hole diameter - four times diameter of pipe. Rule of thumb on hole depth - minimum one/third down (below ground) and two/thirds up (above ground). Rule of thumb on gravel size for concrete - no bigger than one/half distance of pipe to side of hole. Rule of thumb on concrete type - never use 'quick crete', i.e. concrete with additives for one hour curing, it will crack in years to come and sometimes as little as in six months . If you are not using a premix of concrete then use the one-two-three rule: one part cement, two parts sand, three parts pea gravel. When cutting pole to length be sure ends are square - it will cause you plenty of problems if they are not. Remember that concrete shrinks when it cures (concrete does not 'dry', it cures) and actually pulls away from surfaces as it hardens so weld a flange, or spur, to the bottom of the pole for to anchor pole into concrete as it hardens. A flange on one side is sufficient, both sides is overkill. Sometimes I have just drilled a hole thru the pipe and stuck a rod thru the holes with no welding. When digging hole - get below frost line and flare out the bottom of the hole so concrete will make a good plug when poured (make the hole look like an elephant's foot).
Place a thick layer of gravel on the bottom of the hole, or at least a brick but gravel 'seats' the pole better, and set pole in hole on gravel. Do not try to pour the whole concrete batch at once. Make the first batch stiff (thick), position pole in center of hole, and shovel small amounts of concrete equally around the pole. If you shovel too much concrete to one side at once, especially in the beginning of the pour, it will push the pole to one side and you will lose center; be patient and take your time here. Pour enough in first batch to bring concrete about a foot up on the pole. Now take a rod, something like a piece of rebar, but a shovel handle is too thick, and gently 'rod' the concrete, i.e. push rod straight down thru concrete to bottom of hole - be careful not to do so in a manner that causes the pole to lose center. Do this no more than ten to fifteen times, this ensures no air is trapped in mix; if you rod more than that then the mix begins to come apart. Check pole for plumbness all around, not just on one side, with level or inclinometer - hold pole for a few minutes now (good thing for assistant or mother-in-law to do). Do not be lured into thinking that pole is plumb because top is level - that depends on the saw cut; make the sides plumb. Make next concrete batches with more water and gently shovel into hole in small amounts being careful not to pour too much at a time or you will disturb pole plumbness. The reason the second batch of concrete is made with more water is because soupy concrete cures to have more strength. Repeat rod procedure, extending only slightly to level of first pour, and check for plumbness.
At this time set a PVC elbow in concrete that extends out beyond the hole wall and is against the pole and extends up the pole high enough to be above lawn mower or weed eater height. You can cap top of PVC later with downpiece - what is important now is to seal both ends of elbow with good tape to keep debris and concrete out of pipe. I have set elbow in concrete and set it above last pour - your choice - I usually set it in pour at depth below grass root level. Finish pour to top and rod last batch; sculpt the top so that concrete slopes away from pole. If you want, bring concrete to above ground level or leave below ground level so as to add a grass plug later. At this time, pole should be difficult to move because of thick concrete in first pour though later soupy pours will take some time to cure. Recheck for plumbness and push pole to any direction required to be plumb - it should not be far off, if at all, if you have been checking regularly - hold.for a few minutes while you drink a cup of coffee, tea, cola or have a smoke. In about an hour fill the pole with very soupy concrete to at least above ground level - this will add strength to the pole as well as prevent future oxidation (coming from internal of the pole) of the pole at the ground/air interface.
For four meter or larger residential antenna, use a larger diameter pipe than recommended and place a reducer cap on top when ready to install reflector, i.e. if the mount cap comes ready for a 3.5" pipe then use a 4.0" or greater main pipe diameter and weld a reducer cap on top with a 3.5" diameter that the mount cap will slide on. For more info on pole diameter, see wind loading. Remember: When choosing the site for the ground pole be sure that when the dish is rotated from arc to arc it will not touch anything and that it will have a clear view of the satellite arc from end to end.(top of page)
PAD POLE: Where hard rock prohibits a ground pole, or for installations in a parking lot or on a flat roof, it becomes necessary to anchor the satellite dish with a little more creativity. The most easiest is to weld a crosstie leg assembly with a welded support brace going from each leg up to the pole; then weight down each leg to immobilize the dish. I am currently in a rent house, flat roof, so do not want to permanently install my dish in a concrete pad on the roof so I use unopened eighty pound cement bags (not quickcrete with gravel and sand but pure cement) on each base leg as a weight. With rain, over time, it will harden like a rock and mold itself to the base leg. For a rule of thumb, for an installation on a flat roof atop an office building, for a 3m dish, use a total leg base of eight to ten feet (four to five feet per side) and use something like four inch channel for the leg and one or two inch angle iron for the braces (do not use flat bar for braces but you can use round bar). In practice, position the pole and base on roof then level the base with shims so that the pole is plumb then apply leg weights (use a pile of rocks if nothing else). For my system, an eight foot dish on a one floor roof, I have two foot length legs out of one inch angle iron with sixty degree round bar braces from each leg to the side of the pole - all welded. I have come out one-half the leg distance and up at a sixty degree angle to the pole. Note: Often after a weld, the legs will 'pull' a bit. In my case, that occured however on the roof I leveled each leg with shims so the pole was plumb then piled the weights on the legs and and a few rocks around the pole. Remember to check the pole for plumbness after piling on the weights.
In lieu of the 'crude' system described above, you can use a combination of a mount pole outfitted with legs set onto preformed concrete end weights. Preform the leg weights, mass production style, as concrete blocks, use ready mix sacks, i.e. not large aggregate (gravel) and inset a 'J' bolt for both leg attachment and pole leveling. Concrete is stronger the soupier it is so do not wipe water off the top and if need be, on real hot days, place a burlap sack on top and wet it down after your last pour. On real cold days, add a combination of straw, newspapers and rags on top to prevent freezeing. In designing your forms use an assembly that you can bolt to a bottom plate (1" plywood). Make the side boards at least from 2" x 6"s to allow sufficient depth for the 'J' bolt. Depending on the size of dish to anchor you can make the blocks with 2" x 8"s, 2"x 10"s or 2" x 12"s. On the bottom of the form nail (or screw) a 'lip' all the way around (use a 1" x 6") and use this lip to bolt to the bottom plate. The lip and bolt down prevents concrete from oozing out the bottom of the form, use mimimum two bolt downs per side. When cured, remove the bottom plate and hopefully you can dump out the mold and reuse the form - concrete actually shrinks when it cures so you are making a reuseable form.as the finished block will pull slightly away from the form and will come out rather easily but during the pour the form must be bolted down well to the bottom plate. In lieu of 'J' bolts, you can take a threaded rod and then thread nuts and washers to make the anchor in the block. Make a jig for the top (from a 2" x 4") with a center hole to place over the anchor bolt and thread a nut over the exposed bolt to keep the bolt in place and vertical and to be sure the bolt does not sink into concrete. Use the top jig, or another board, to level the top before slipping in bolt, i.e. wipe off excess concrete from pour. Use a mini-level (sometimes called a torpedo level) to guarantee the bolt stays vertical. Make the block in one pour and use medium stiff concrete at time of pour but not too stiff that bolt will not slide in easily - the bolt should slide in and concrete ooze around it easily otherwise anchor will not be set to its best capability. Remember, concrete actually shrinks as it cures so do not but in a straight bolt without something to anchor it in the concrete or you will compromise its stabilizing effect on the dish mount. Do not use anything less than a 3/4" diameter bolt. If you are using allthread for the bolts and/or have in mind to saw off the bolt tops after concrete has cured, i.e. to level all the emplaced bolts, thread a nut onto the bolt before sawing so that after the cut you can work the nut off and reconstitute any threads damaged by sawing.
The last real option to anchor a dish without a ground pole is to pour a complete concrete pad. The major aggragation to this is inseting the bolts to correctly align with the dish pole support structure. The other option to inseting bolts is, after concrete pad has completely cured, use an epoxy system to anchor the required bolts. This technique requires drilling the proper hole into the concrete then using the epoxy system to secure bolt; a manufacturer's variation on this is to epoxy (into the hole) the unit the bolt will thread into then, of course, install bolt. These are proven, structurally rated epoxy techniques and make a very nice installation; check with any high quality hardware store to located the product (read all instructions when using the epoxy system as there is little for error once you begin the epoxy process). To properly mark hole locations, place the mount on the finished pad then mark with a chisel where to drill or, better, drill a starter hole with a masonry drill bit before moving the mount to drill the correct size hole.
The other option, for a full ground pad, instead of inserting bolts, is to pour the pad (to level the install site) then use a brace-leg-weight system to anchor the pole. For the pad, set the pole with legs at the proposed location and mark the size pad desired; then, remove pole out of the way (of course), build your form. For a weight anchor system, minimum pad thickness is using a 2" x 4" for the form edges for a 2.0m or less diameter dish and go to a 2" x 6" for a 3.0m dish and a 2" x 12" for anything greater. Be sure to frequently stake the form perimeter as concrete is heavy and will push out on the form. Nail form edges into each other. Be sure top of form is level in both directions. If pad site is unlevel and the bottom of the form is not touching the ground in any place then fill inside of form with dirt to prevent concrete leakage and pack the dirt firmly. Try to mix all concrete you will need in the beginning then shovel into form. Resist the temptation to throw in rocks/bricks, etc., to fill your pad quicker. When form is halfway filled, lay in a layer of concrete wire mesh then finish pour and level off top with a board, i.e. scrap off excess concrete. Do not scrap off excess water on top of pour; if anything, after an hour, spray more water on top of curing pad. The extra water on top will assist in preventing cracking. In laying the mesh on this small of a job, it is best to do so in middle of pour rather than lay on ground and fill concrete on top and try to 'shake' it up. The mesh is not so much to add strength to the concrete but to hold it together over time (maintain its structural integrity) should the pad crack (due to whatever reason). In case of excess freeze-thaw phenomena locations, i.e. in 'cold' country, using a weight-leg pole assembly, rather than insetting attachment/leveling bolts in the concrete, allows for easier leveling adjustment should the pole become non plumb. When running cable, bury it, if possible, to the pad then run through conduit atop pad to the pole; attach conduit with strapping clamps to concrete using plastic screw anchors inserted into drilled holes (use masonary bit) in the concrete.(top of page)
WIND LOADING:The bottom line on wind loading (on the surface of a dish) is the bigger diameter the dish the more wind it traps and the more the dish faces into the dish the more wind it traps. Mesh dishes act as solid dishes at about fifty miles per hour though will still experience approximately 40% less force than a solid dish. To calculate the pressure on the base of a pole, or where ever the pole is attached to a constraining rigid structure (for instance, side wall of a house), multiply the pole length by the factor in the chart, for the desired windspeed, to get pounds per square foot (psf); then divide by 144 to get pounds per square inch (psi). This is a crude guide for you as other factors come in play in determining actual shear forces on a mount pole from wind - dish weight does factors in, i.e. the heavier the dish the more force it will bear if the dish begins oscillating (which contributes to fatique), and it changes the pole strength factors if you have poured concrete into the pole. From the pressure on the pole base and the manufacturer's characteristics of the mount pole you can see if your chosen pole diameter is large enough and its thickness sufficient to resist failure under maximum winds. Believe me, nothing is more aggravating than dealing with a bent mount pole after a windstorm. Use dish manufacturer's guidelines in choosing a mount pole - do not leave it to chance, especially on heavy large dishes. Remember, a good ground pole installation, or pad mount, and depth of pole, prevents a dish from eventually rocking or leaning in the ground but does nothing to resist shear bending above the ground. For dish diameter below 2.5m, with minimal pole height, you can use schedule 80 (USA ASTM code) 3.5" diameter pole. For dish diameter 3.0m using and regular height poles (mesh, fiberglass or solid dish) and taller poles for diameter 2.5m, use schedule 40 3.5" diameter pole. For taller poles above ten feet, in the previous two examples, use some type of side wall support or turnbuckle/wire rope bracing system or expect wind action on the Ku satellites. For 4.0m dishes and commerical installations (not az/el type mount), use schedule 80 pole and go to 4.0 and greater pole diameter - ask dish manufacturer. For these larger diameter dishes they often refer to the 'pole' as a pedestal and usually the manufacturer will recommend and provide the pedestal or a tower for dish support.
Under no conditions, use PVC (plastic pipe) for any dish mount
(I have never heard of it being successful), and never underestimate
the power of inclement weather to damage your dish. For commercial
installations, I have installed retainer clips around dish lip
attached to wire rope (3/8" wire rope minimum) attached
to 'J' bolts in concrete posts so if the mount failed (not the
pole) then the dish would not fly around. Although we think of
failure of the pole, the shear strength of the bolts in the mount
are to be equally considered in your design criteria in wind
loading. In summary, if you have continued worries about pole
failure, have an engineer calculate wind loading forces on reflector
and the force moment at the ground/air interface (bottom of pole)
and choose pole diameter accordingly. I also use three support
cables (3/8" wire rope minimum) placed two/thirds of the
way up the pole for stabilization when needed to stay on track
in wind or for a free standing tall pole, and tighten with a
turnbuckle. Weld 'eyes/ears' on pole for wire rope and anchor
at a thirty degree angle from pole to 'J' bolts seated in concrete
pods. Your local hardware store will have everything you need.