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Sometimes each rod in a reflecting plane is counted as one. Other ratios are possible by using two rods of differing diameters, or by adding a third rod. Preamplifiers or Mast-mounted amplifiers - These should be mounted as close to the antenna as possible. If such a splitter came between the power injector and the mast-mounted amplifier then the DC would go some place unintended. If there were a 25-inch diameter hole through the crown of the tree, and if the dish could be pointed at the satellite through that hole, then the tree would have no effect on reception (until the wind blew). If you see two dropouts that were N minutes apart then you will probably continue to see dropouts every N minutes. The first problem is that your HDTV is probably not on the roof, thus you can’t see the signal readout. Distribution amplifiers - These are simple signal boosters.

The above numbers are approximate. The antenna might not be high enough above obstacles outside the house such as trees. A perfectly vertical metal vent pipe is invisible to TV signals, but its flashing at the roofline might not be. A signal strength meter is not as useful as you might think. A portable signal meter based on one generation will not find the correct antenna aiming/positioning when the TV’s demodulator is of the other generation. This is fading. There is no cure for it, but a stronger antenna will make it less likely. The interfering station can be very far away and very weak, yet it can contribute enough "noise" to make the closer station hard to receive. Metals reflect signals. A metal object 8 inches long is big enough to reflect UHF. Dropouts (weak signals) - On DTV channels you will never see snow, ghosts, or interference, but you will see dropouts. Exceptions are aluminum siding, stucco (which has an embedded metal screen), and foil-backed insulation, all of which totally block all signals. Wires and metal pipes effectively reflect VHF, as do plastic pipes containing water. There should be no horizontal or diagonal wires or pipes in front of the antenna.

For twin-lead to be 300 ohms the spacing between the wires must be about 6 times the wire diameter (more if there is insulation). When adjacent channel stations broadcast from the same tower or adjacent towers they must have an agreement that neither will exceed 10 times the other’s power. Since this is a voltage number it must be squared before multiplying it by the ERP to get the power radiated in your direction. A 6 dB attenuator will reduce a signal to one-quarter of its power (one-half its original voltage). In a desert, plywood becomes so dry that it causes no signal loss at all, even for UHF. Even the largest crimp tools will hurt your hands. The record will say whether the antenna is directional or omni-directional. If you have some of these local obstructions, you will probably need a stronger antenna than this site recommends. The Consumer Electronics Association (a manufacturers group) runs this site. This equipment costs two or three times as much as consumer grade equipment, but it is more ruggedly constructed.

Equatorial mounts are much simpler and much more common. Equatorial mounts normally lack one motor (the latitude motor) and thus track only geo-stationary satellites, while az-el mounts can track the whole sky. Bandwidth - A wideband antenna will pick up all the channel in a band, while a narrowband antenna will receive a few channels well but most channels poorly. There are some frequency selective filters that can "trap" out a channel, but they are seldom able to reduce an adjacent channel by more than half. BNC connector - This is a very common high frequency connector, but it is almost never employed in TV antenna systems. But the only connector generally used for TV antenna systems is the F connector. Real antenna people never do these things. It is inserted into the antenna cable between the amplifier and the TV. If a balanced transmission line (such as twinlead) is connected directly to an unbalanced line (such as coaxial cable) the two lines become a long-wire antenna, which is undesirable for VHF and UHF. It employs a resistor network designed to not cause any reflections in the transmission lines. They will never make reliable crimps.

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