FM Reception Tips

Courtesy of Winegard Company
3000 Kirkwood St.
Burlington, IA 52601-2000

INTRODUCTION

The first step toward quality FM/stereo reception is a quality FM tuner or receiver. However, even with the best equipment money can buy, your tuner may not produce as good a sound as an inexpensive mono FM portable. Why?

A small, mono FM radio will sound good on a very minimal signal because the speaker will filter out noise and distortion. Plus, it is not required to separate the stereo channels. However, you don't get the lifelike sound reproduction. That's the purpose for buying expensive FM/stereo tuners and receivers.

If you want real high-fidelity, true-to-life stereo sound reproduction with no background noise or distortion then you must have at least 3 microvolts, (3/1,000,000 of a volt) into the receiver, which means you also need a top performance FM antenna.

Winegard offers a variety of specially designed and constructed FM antennas. By deciding which Winegard FM antenna you require, you can get FM/stereo sound reproduction your receiver is designed to provide.

This "FM Tips" brochure is designed to provide information on FM/stereo reception and is a guide to help you select the right Winegard FM antenna for your needs.

WHAT IS FM?

The letters "FM" stand for Frequency Modulation, that is, the carrier frequency is modulated (regulated or varied) by an audio signal. The FM band is widened instead of narrowed. The wider the band of frequencies employed, the greater suppression of noise or static. This results in a clarity and lack of distortion and interference unknown in AM, or Amplitude Modulation. FM occupies the 88-108MHz band which is located between channels 6 and 7 of the TV band.

FM is broadcast in either monophonic or stereophonic. Monophonic was the only method of FM broadcasting until 1961, and means the sound reproduction is being transmitted via a single channel. Stereophonic has accounted for the increasing popularity of FM, and means the sound reproduction is being transmitted via two or more independent channels through a process called "multiplexing." FM stereophonic signals have only about half the reach as monophonic transmitted at the same power level.

HISTORY

The discovery and development of FM or frequency modulation radio is one of the lesser known accomplishments in electronics yet perhaps one of the greatest.

FM was conceived about 1933 by Edwin Howard Armstrong, a noted professor of engineering at Columbia University and a recognized genius in electronic circuitry. He contributed two basic circuits to early radio which are still at the heart of most modern radio/ television transmitters and receivers.

In 1932, Armstrong conceived the revolutionary idea of FM. Instead of transmitting radio waves over a narrow band of frequencies, like AM, he allowed them to swing over a very wide band of frequencies. He discovered frequency modulation was capable of transmitting intelligence with a clarity and a lack of distortion and interference unknown in amplitude modulation. Thus, Armstrong had created an entirely new radio system, FM!

To demonstrate the quality and versatility of FM, Armstrong conducted an historic test on November 24,1934. On a single FM carrier wave he transmitted: (1) two programs from the NBC networks; (2) a facsimile reproduction of the front page of that day's New York Times; and (3) a telegraph message. This proved FM as a basic new system was capable of linking all types of communications.

Armstrong worked diligently to promote the acceptance of FM. He constructed a full-scale FM station as an experimental operation while he continued to improve his FM designs. By 1940 he held 16 patents.

In March, 1940, the FCC replaced the Channel 1 TV allocation with FM for a total of 40 channels sufficient for more than 2,000 FM stations. In addition, the FCC ruled that all television sound be changed from AM to FM, clearly the superior aural broadcasting medium.

In June, 1945, the FCC ordered all FM radio be transferred from its 50 megacycle band to a new band of frequencies between 88 and 108 megacycles.

From that point on the qualities of FM, noise-suppression and the ability to carry the full frequency range of sound perceptible to the human ear has attracted a growing band of discriminating listeners and dedicated FM broadcasters. Finally, in 1961, the FCC authorized the use of a split-band system of stereophonic broadcasting over FM channels, a technique whose underlying feasibility Armstrong had demonstrated in an historic multiplexing experiment as early as 1934.

Hundreds of millions of radio sets equipped with FM are now in use in the U.S. The number of FM stations on the air now reaches 5000. FM has truly become the dominate radio/TV communications system in this country and should remain so through the rest of the century.

CHOOSING AN ANTENNA FOR FM

Before purchasing an FM antenna you must decide what type you really need. Define the problems you need to overcome and consider your location. The key to good FM/stereo reception is to get the maximum direct signal from the transmitter and minimum amount of reflected signal.

If you live in a metropolitan area or are located close to an FM transmitter, an antenna with sharp directivity is needed rather than a high-gain antenna. A good FM antenna should reject unwanted signals coming from a different direction or bouncing off obstructions. Good rejection depends on the antenna's front-to-back ratio and beam width. Front-to-back ratio is the antenna's sensitivity to signals coming at its rear. The higher the ratio, the better rejection of unwanted signals coming from behind. The beam width indicates the angle at the front of the antenna within which it can best receive the FM signal. A narrow beam width makes it difficult for unwanted signals to be received from the side.

From 2 to about 25 miles out is what is referred to as the "prime" FM reception area. Here, multipath distortion is less of a problem, and a medium gain antenna with a moderate beam width should be perfect. However, if you wish to receive FM stations in different directions you'd probably want a directional antenna with rotator.

From 20 to 40 miles out is the normal reception area, and an antenna with good gain is needed. Again, depending on the location of the FM transmitters, you may want a directional FM antenna with rotator.

If you are located more than 40 miles out you are in the "fringe" area. You'll need a "hot antenna," that is, one with high gain. If stations come in at the same or adjacent channels the antenna must be directional. Again, a rotator may be required. If the antenna alone doesn't provide enough gain, the use of a Winegard amplifier may be helpful.

VHF/FM AND VHF/UHF/FM ANTENNAS

Broadband television/FM antennas (broadband meaning more than one band of frequencies) are basically a compromise for FM but can be sufficient for local FM/ stereo reception. A broadband antenna has only about one-half the gain of a simple FM antenna. This difference would not be important in a prime reception area, but is highly significant if you're trying to receive long-distance FM signals. For best possible FM, we recommend you install a separate FM antenna.

BUILT-IN FM ANTENNA

The FM antenna built-in to your FM receiver can give you clear reception providing you are located in a strong signal area and there's an unobstructed signal path from the transmitter. But, it will not receive FM signals from a remote FM transmitter very well, nor will it reject multi-path reflections. If you own a high-quality FM tuner or receiver and want the best quality FM/ stereo sound, you need an external FM antenna.

USING A ROTATOR

For the discriminating FM buff who wishes to receive FM stations from different directions the use of a rotator is a "must." A highly directional, high gain antenna and rotor should be able to pull in 90% of all FM stations within 200 miles (depending on receiving antenna height and transmitting antenna height.)