West Lane Translator

THE ROLE OF THE RECEIVING ANTENNA IN UHF TRANSLATOR RECEPTION

By Daniel Mooney
Translator Systems Engineer
(Up dated by Larry Bloomfield, November 2007)

In areas served by UHF television translators, complaints are frequently heard that reception is poor. There are several possible reasons for poor reception, some of which have to do with the quality of the signals as received at the translator site. These "input" signals are often degraded by unfavorable atmospheric conditions, by ghosting which is caused by signal reflections from mountains and other large objects, and by interference from power lines, electrical equipment, and other radio and TV signals. A translator will faithfully reproduce the signal at its input and this signal is not always clean. (FYI: There are VHF translators. We don't have any here in Florence, but Mapelton does, however.)

There is, however, one part of the system that you have some control over: the receiving antenna.

In order to assist translator system users in pulling in the best possible signal, what follows a list of tips for installing an antenna or "tuning up" an existing antenna.

1. Make sure you have the right antenna. The older types of UHF antennas that were designed for channels 70 to 83 do not work well on channels 14 through 60. (The old TV channels 70 to 83 are now being used for cellular telephone service and the FCC is moving all TV stations from channels 52 and above to lower channels as the digital transition occurs.) The "bowtie" type antenna is a favorite and performs very well on UHF channels. There are other types that work quite well also.

Log periodic

Bowtie

Examples of UHF Antennas

All antennas should be aimed with the "bowties" facing the translator tower.

2. Install your antenna "in the clear" above trees, buildings, or other obstructions (if possible). Be sure it is in a safe area, away from any and all power lines. If this results in a down-lead (the wire from the antenna to the TV set) that is over about 50 feet long, consider installing a UHF preamplifier or "booster". With a good preamp you can use enough down-lead cable to position your antenna at the most ideal location. Also consider a preamp and/or a new TV set if you have an older set that does not have a good sensitive UHF tuner.

3. Have someone move your antenna vertically, either up or down on its mount while you watch your set. Switch among the various channels with the antenna at different heights instead of viewing just one channel. Locate the antenna position which results in the best overall reception on all the channels. This may be necessary even if you have a clear unobstructed view of the translator tower. Signal reflections from the ground in front of your receiving antenna or other nearby objects such as buildings usually cause "hot spots" and "cold spots". Moving your antenna, especially moving it vertically, even a foot or two can have a dramatic effect on signal strength.

Twin lead

Coaxial (Coax) cable

with F connector

4. If your down-lead is of the twin-lead type (a brown or black colored cable with two wires embedded along the edges), replace it with coax. You will encounter too many problems dealing with this type of antenna lead-in wire than is worth the effort to keep it.

In many ways, a coaxial cable (type RG-6 is best) down-lead is easier to install as it can be run in any manner whatsoever. The wave or television signal energy is totally contained inside the cable and the only way to hamper or degrade the signal it is carrying to your TV set is to squash the whole cable. However, matching transformers must be used at the antenna and at some older TV sets to go from the two screw terminals to the coaxial cable "type F" connector. These matching transformers must be capable of operating efficiently at UHF frequencies and the outdoor ones must be weatherproof types. Ask your dealer for the proper ones.

type F connector on coaxial cable

Do not connect the coaxial cable directly onto the two screw terminals at the antenna where the flat twin-lead should go at your set. You will be cheating yourself out of most of the available signal. Most TV sets made nowadays have the coaxial type F connector for input, so these sets are ready for the coaxial down-lead cable. The type F connectors can be tricky to put on the cable for those not used to them. A TV shop can put them on for you if you have trouble.

Please keep in mind that UHF translators are usually designed for operation at between 1 and 1000 watts of output power whereas a full power UHF station transmits thousands of watts. We must cover a large area with such low power so we have to spread it pretty thin. The transmitting equipment is only half of the total system. The other half is your receiving equipment which, like the translator, it must be kept in top condition if the maximum potential of the system is to be realized.

When the transition to digital takes place here in Florence, you should not have to change your antenna, no matter what some uninformed salesman may tell you. You may need a set top box converter to convert the new digital signals to analog. All television sets manufactured on or after March 2007 must have the capability of receiving the new digital signals (when they become available).