This page provides technical information related to:
written by Scott Holisky, one of our transmitter gurus Problems Affecting Rural TPT-2 Viewers Signal level changes occur daily to almost all rural Ch 2 viewers. Sometimes these changes become so dramatic as to cause interruptions in the picture and sound, lasting from a few minutes to several hours. Below are explanations of two of the major causes of reception problems in outlying areas. Tropospheric This effect clears up once the wind blows and begins to mix the different air masses. Ionospheric This effect generally starts around (local) noon, and can last into the evening hours. Frequently, "northern lights" are visible during days with high levels of solar activity. Although there is no "cure" for the reception problems above, a well installed antenna system may help eliminate effects from minor disturbances. Guidelines: (Recommendations for improving reception)
Improving TPT-17 Reception - External Antenna Recently we have all begun tuning in UHF stations, those TV channels that used to be vacant. The change in viewing habits has brought many of us to the back of our sets, wondering what to do next. A brief description of what is generally involved in obtaining quality UHF reception follows. Whether you attempt to install a system, or elect to have it professionally done, knowing what it takes to make it work will be an advantage to you. UHF TV covers channels 14-69. The frequency is much higher than VHF. This higher frequency means two important things, first, the antennas will be physically smaller and second, the wire we use to bring the signal from the antenna to the set can reduce the signal level very quickly when using long runs to your set. Let's look at the cable first. The best choice you can make is to buy a premium quality, 100% foil shielded, coaxial cable. The old "twin lead" won't do. The connectors for this cable are called "F" type, proper installation requires a "crimping tool" to insure good mechanical contact. Transformers. Connections on your TV and antenna are standardized and either end maybe different. The two types are: 75 ohm, which accepts the "F" type connector directly from coaxial cable. The second type is 300 ohm, which has 2 screw heads spread about one inch apart. In order to maximize signal transfer from your antenna/cable/set the transition from an "f" fitting to the screw terminals (or old flat lead hook up) requires a "300:75 ohm balun transformer." These transformers will work in either direction, the antenna or set, it makes no difference. When purchasing these be sure they are rated for VHF/UHF use. Antennas used for television reception are generally rated by a mileage factor. Depending on your distance from the transmission point (in our case 694 & Victoria, north of downtown St. Paul) you should select one appropriately rated. I recommend that the selection should error on the high side, a little larger antenna is better. If your plans are to add a second television set, or if the coax length is excessive (over 75' or so) again, purchase the next larger antenna size. The guidelines here are vague because each area within our viewing range could require a different size antenna. If you are going to install your own system, I recommend you purchase the equipment from a knowledgeable local vendor. The cost of the antenna may be more than what a "discount" store would sell them for, but, the correct selection will save you money and increase your viewing pleasure. Your new antenna will require mounting. Putting antennas in the attic (with rare exception) generally results in poor performance. Unless you must try an inside mounting scheme, I recommend you stay away from it. Antennas placed on chimneys are going to corrode and fail at a much faster rate due to the flue gasses (this is another mounting scheme to avoid). Outside rooftop antennas need to be mounted away from surrounding objects. The antenna height is a lot less critical than what most believe. A minimum height of the length of the longest antenna element is a good guideline. Installing the antenna high in the air is only required to overcome nearby obstacles. Once you are above nearby obstacles, there is seldom any advantage to going higher. Lightning protection should be included in your installation. Drilling a hole in the roof and snaking the coax between the walls may be a neat visual installation, however, I've seen many walls and ceilings removed by the fire department to put out flames from a lightning strike. The safest path to your TV is to run the coax down the roof to a ground rod/lightning arrestor and then into your house at near grade level. Your local antenna dealer should be able to guide you with building codes and required equipment. Pointing your antenna. There is now a thick "putty like" tape that is on the market for weather proofing connectors. It works real well. Installing your own antenna system can be fun and rewarding. There are a multitude of combinations to choose from when hooking up TV's, VCR's, games, switch boxes, etc. Your local library or book store should have books that go into greater detail about these special installations. Obtaining the best possible reception of your supported Public Television stations is important to us both. Please don't hesitate to contact us if we may be of further assistance. |
