Installation Of Mast

Masts
Most antenna hardware catalogs list a wide variety of mounts and masts. Most however, are variations of a few basic types. By taking into account signal strength and ease of installation, it's not difficult deciding which site, mount, and hardware to use.
A mast (Figure 4-1) is used in every installation. The mast is the vertical tubing that supports the antenna. Conventional masts are available in 5 and 10 foot lengths. Telescoping mast units (Figure 4-2) are available in 20, 30, 40 and 50 foot lengths. Each type is available in various wall thicknesses that provide different degrees of strength and rigidity. Your choice will depend on the height, weight, and size of the antenna being installed and also on wind conditions in the area.
Both conventional and telescoping masts are available in galvanized steel and in high Tensile, acrylic-coated steel. Acrylic-coated masts are preferable because of their greater strength and durability.
MOUNTING SITES AND RELATED PROCEDURES
Attic Installations
An attic installation (Figure 4-3) may work in areas where strong signals are present. In most cases, an attic installation is the easiest, fastest, most economical, and most convenient installation. There are a few conditions however that can prohibit an attic installation. Shallow attics that are obstructed by rafter supports may not accommodate the size antenna required for the installation. Most attics are not large enough to accommodate multi-antenna arrays and rotors. Also, aluminum foil on insulation, aluminum or steel siding, metal gutters at the attic level, and metal lath under older plaster walls all can interfere to some degree with reception.
Fig. 4-3. A typical attic installatIon.

To determine if an attic installation is suitable, take a test antenna, a field-strength meter and a portable TV up into the attic and check the signal level and picture quality. If the signal level is sufficient and there is room enough to properly orient the antenna, assemble the antenna in the attic and attach one end of the transmission line to the antenna terminals. Then prepare the mount for the antenna.
Several roof Type mounting brackets (Figure 4-4) and swivel mounts (Figure 4-5) are adaptable for use in attic installations. The mounting bracket is used to attach the short mast to a rafter or rafter support. The antenna is then mounted on the other end of the mast. The antenna however, must not touch the attic floor. Also, remember that the antenna should be attached to the mast right side up, even though the installation appears to be the reverse of an outside installation.
Fig. 4-4. Fig. 4-5.
Examples of swivel mounts that can be used in attic installations.
An alternative method of mounting the mast is the flatten one end of the mast with a hammer and drill a hole in it through which a nail, screw, or bolt can be inserted for securing the mast to a rafter or rafter support. However, this method requires more time and effort than does the bracket method.
Instead of using a mast, you may suspend the antenna from the inside of the roof with guy wires or nylon rope. But don't let the guy wires touch the antenna elements. They will short out the antenna.

Once you have the antenna mounted or suspended, you are ready to run the transmission line. If at all   possible, keep it indoors. Coaxial cable (Figure 4-6) is  the best transmission line for any antenna installation. It should be used instead of twinlead even in attic installations. Selection and installation of the correct transmission line is described in the chapter beginning on page 15.
Fig. 4-6. CoaxIal cable, the preferred type of TV transmission line.
After you have run the transmission line, use a compass and field-strength meter to orient the antenna toward the signal source(s). Check the picture and sound on all channels before you tighten down the clamp that secures the antenna to the mast.
Some manufacturers make special antennas for attic installations. These antennas however, tend to be omni~directional. This means they intercept signals equally well from all directions. Consequently, they will also pick up interference more readily than a good directional antenna.

Chimney Mounts
Chimney Mounts (Figure 4~7) are used more frequently than other types of mounts, but they often are not the best option. Although they are relatively easy to install, the smoke and gases from a chimney can shorten the life of the antenna and significantly impair its performance.
A chimney installation is practical only if the chimney is sturdy and vertical. Never mount an antenna on a deteriorated chimney. During moderate too high winds an unguyed mast taller than 10 feet can exert enough leverage to break off an unstable chimney.
If you choose a chimney mount, use enough mast to place the antenna above most of the smoke and gases. However, to avoid overstressing the chimney,  do not mount the antenna more than 10 feet above the top of the chimney. If the height of the antenna must exceed 10' to receive satisfactory signals, the mast must be properly guyed. CYhe correct method of  installing guy wires is described in Chapter 7.)

Securing the chimney~mounted antenna and minimizing the stress on the chimney requires the mounting straps to be properly spaced. The top strap should be placed as high up on the chimney as possible. If the chimney has a crown or projecting cap, place the to strap directly under it. The bottom strap should be placed 4 feet below the top strap. If the chimney isn't long enough to permit this, place the bottom strap as far down on the chimney as possible. If the mast must be 10 feet above the chimney top, don't use a chimney mount unless you can space the straps at least 30 inches apart. For masts less than 10 feet above the chimney top, the straps should be spaced no less than 24 inches apart.
Be sure the straps are level, with no kinks or twists. The easiest way to level straps is to line them up along the nearest course of bricks. Straps should be centered on the bricks-not over the mortar joint. Pull each strap tight, line it up so that it's level, and then tighten it just enough to hold it in place.
Before the straps are tightened completely, fasten the mast to the mounting bracket. (1t is assumed that the antenna has already been clamped securely to the mast, and one end of the transmission line has been connected to the antenna terminals.) Align the mast so that it is vertical. Then completely tighten the mounting straps. Next, orient the antenna. Finally, tighten the clamps that hold the mast to the mounting. Be sure the clamps are tight enough to prevent the mast from being rotated by the wind load on the antenna.

Roof Mounts
There are two basic types of roof mounts: a base mount (Figure 4-8) and a tripod (Figure 4-9). Tripods are stronger and more rigid than base mounts, but they are also more expensive. When given a choice, use a tripod.
10 TOOLS, MASTS & HARDWARE REQUIREMENTS
However, if cost savings or limited space require it, a properly guyed base mount will usually work. Unlike a chimney mount, a base mount holds the mast at only one point, the bottom. Consequently, the mast also must be supported by guy wires, regardless of the mast length.
Correct installation of either type of roof mount requires great care and should not be attempted without a helper. Both types of mounts should be secured to the roof with either bolts or lag screws. These should be screwed into only solid wood like a rafter or a truss section. You can locate these with a stud finder.
If you must fasten the mount to the roof in an area where a bolt or screw cannot reach a rafter, send your assistant into the attic with a large square of wood 1-1/2" thick, to act as a backing plate. Have him hold this wood against the entry points of the screws or bolts so that the mount is firmly anchored in both the roof sheathing and the wooden block. This will give the mount needed stability.
When installing a base mount, attach the base plate to the roof in the manner lust described, and place the mast (with antenna, guy ring, and guy wires attached), into the U-bolt that has been fastened loosely to the mount. Do not let the bottom of the mast touch the roof; it may tear a hole in the shingles.

Since a base mount must be guyed, an easy way to raise the mast is to first fasten one of the guy wire screw eyes to the roof peak on the end of the roof opposite the direction in which the antenna is lying. Run the end of the guy wire through the screw eye. Have your assistant slowly raise the mast while you pull the guy wire through the screw eye (figure 4-10). When the mast is vertical, the guy wire you are holding will be approximately the right length for permanent installation. Temporarily secure this guy wire. Install the other guy wires while your helper holds the mast in a vertical position. Check the mast with a level as you tighten and permanently secure each wire. When the mast is vertical and each guy wire has been tightened, orient the antenna and firmly tighten the U-bolt (clamp) on the base mount.
Tripods, as noted earlier, are a stronger, more rigid type of roof mount. The most common tripod mounts are 3, 5, and 10 feet high. The 3 foot tripod is most commonly used. A tripod mount can be installed and leveled before the mast is inserted. It should always be mounted so that the antenna can be folded down along the peak of the roof. This will enable you to lower it more easily should repairs or adjustments become necessary in the future. Even though tripods are very stable, any tripod-mounted mast over 10 feet high should be guyed
Ensure the sturdiness of the tripod by anchoring. To protect the roof, use a pitch pad seal under each tripod leg (Figure 4-11). Coat all lag bolts with roofing tar or other sealant to prevent leaks around them. Roofing tar or silicone should be used liberally around all holes, bolts, screws, nails, and eye screws.

Wall Mounts
Many types of wall mount brackets are available. However, many of them are poorly made and will not withstand more than a moderate wind. Buy only the best quality wall mount brackets (Figure 4-12).
When installing a wall mount, space the brackets as far apart as possible (or practical). Generally, the farther apart you space the brackets, the stronger the installation will be. Be sure the brackets extend out from the wall far enough for the mast to clear the roof eaves. As with roof mounts, screw wall mount brackets only into solid wood, and use caulking or other durable sealant around screws.

Mounting from the Ground
Many times you will not want (or will not be able) to mount an antenna on the roof. One of the best alternatives to roof mounting is mounting from the ground (Figure 4-13). With a firm base support and one or more wall mount brackets, a ground mount installation is exceptionally sturdy and long lasting. A good ground mount may also eliminate the need of guy wires.
Correctly preparing the base of a ground mount is very important. The antenna mast should rest on something more solid and stable than just hare earth. If your installation site is on a solid deck or patio, the base is already prepared for you.
When you have to prepare the base yourself, dig a hold about 2 feet deep at the spot where the mast will contact the ground. Remember that the base hole must line up with the wall bracket(s) so that the mast will be vertical. A plumb line and bob suspended from the roof eave can be used to determine the correct positions of the base hole and wall brackets (Figure4-13). Use bricks or flat stones in the bottom of the hole as a footing to prevent the base of the mast from moving. Concrete can also be used as a footing but you'll have to wait for it to dry before you can put up the mast.
Once the base is prepared, mount a wall bracket at least 10 feet above the ground or as high as possible. Remember, the farther apart the wall brackets are placed, the sturdier the installation (figure 4-13). If there is 5 feet or more left between the first wall bracket and the roof eave, add another wall bracket. Be sure the base hole and the wall brackets line up so that the mast will be vertical. This can be determined easily by suspending a plumb bob and line from the roof eave into the base hole. Also remember that the wall bracket(s) must extend out from the wall far enough so that the mast clears the roof eaves. Be sure the screws of each wall bracket are anchored in solid wood. Screw them into the wall studs.
Firmly clamp the antenna to the upper end of the mast. Insert the mast into the base hole or rest it on the deck or patio. Vertically position the mast by "walking" it up hand over hand. Rest it against the wall bracket(s). Loosely fasten the mast to the wall bracket(s). After determining that the mast is truly perpendicular, tighten the bracket(s) a little more. Next, orient the antenna. After the antenna has been oriented, securely tighten the wall bracket clamps around the mast. Finally, if a base hole is being used, fill in the hole and firmly tamp the soil around the base of the mast.

Telescoping Masts
A telescoping mast (Figure 4-14) is used in installations for which standard 5 or 10 foot lengths of mast stacked together would not be sufficiently strong or rigid. A length of telescoping mast is stronger and more rigid than the same lengths made up of standard mast pieces stacked together. Because of their additional strength, some telescoping masts used with ground mounts can be extended up to 15 feet above the roof line without requiring guy wires. Another advantage of telescoping masts is that they can be easily adjusted to odd heights without having to cut the tubing.
Because telescoping masts are heavy and require firm bottom support, they should not be used with chimney or wall mounts. However, because ground and roof mounts do provide bottom support, telescoping masts can be used with these mounts to provide additional height.
For extra strength when installing large antennas, use a telescoping mast that is one size larger than actually needed. This will permit you to attach the antenna to the mast section immediately below the topmost one. This section is larger and stronger than the topmost section because it is reinforced by the 1-1/4" diameter section that remains inside.
When installing telescoping masts 20 feet or shorter in length, lay the mast on the ground and extend it to the desired length. Prop up the small end on a stable support and attach the antenna and transmission line. Then connect the bottom of the mast to the base mount and walk up the mast to its vertical position. (Use a base mount that will swivel!)
For masts over 20 feet long, securely mount and guy the bottom section first. Then attach guy rings and wires to the rest of the sections. Mount the antenna on the upper section, secure its guy ring and the transmission line. Using a person to hold the guy wires to each anchor point, raise each section one at a time, starting with the top. Tighten the wires after the mast is fully extended.

Vent Pipe Mounting
Vent pipe mounting (Figure 4-16) secures the antenna and mast to the plumbing (gas) vent that comes up through the roof of the house. This type of mounting should be used only for the smallest antennas, and then only when economy absolutely demands it. Vent pipe mounts are not sturdy enough for medium and large antennas. Even a moderate wind or ice load may ruin the installation and damage your customer's property.
Standard vent pipe mounting hardware is available. However, it should be used with great care. Most vent pipes are made of soft materials like copper or orangeburg, which are easily crushed or dented by the stress exerted by the mounting bracket.

Towers
Antennas are mounted on towers (Figure 4-17) when exceptional height (35 feet or more) is required for adequate reception or when an unusually large antenna array must be used. Although they are very sturdy installations if properly installed, towers can be very difficult and dangerous to erect. Tower manufacturers' instructions and specifications usually include a large number of warnings and precautions that must be strictly followed. The best advice that can be given about tower installations before attempting one of your own, is to work with an experienced tower installer on one or more installations. If possible, have an experienced installer assist you with your first tower installation. If you do find yourself involved in a tower installation, be prepared for some heavy work and for the possibility of having to climb well above the height of the average roof.
If you must climb a tower, use an attachable work platform with a safety ring and safety belt. These are available from some tower manufactures. CAUTION: Before climbing any tower, first check the condition of the structure and the guy wires to make sure the installation is safe. Even a newly installed tower may have defects that make it dangerous to climb.
In most cases, a properly guyed 40 or 50 foot telescoping mast can be substituted for a 40 to 50 foot tower installation. It is not only easier and less dangerous to install, it is also significantly less expensive. A detailed discussion about the various types of towers and the procedures for installing each of them would require more space than is available in this manual. The most accurate and helpful sources for such information is the extremely detailed instructions that most tower manufacturers provide with their towers.