FM antenna: principle of operation, universal model for a do-it-yourself music center, signal attenuation

Despite the rapid development of the Internet, many people still prefer to listen to their favorite radio stations. Demand always keeps up with offers, due to which the number of broadcast programs has increased so much that each user can choose a wave to his taste. But there is one drawback - high-quality radio reception is not possible everywhere. You can solve this problem with a high-quality FM antenna, which you can design yourself.

The principle of operation of radio receivers

Stable operation of such a device is possible only if an optimal signal level is created at the input, exceeding the required threshold. Experts call this parameter the sensitivity of the unit. Only if the received signal is above this threshold, the radio will work well, and the user himself will be able to enjoy the high-quality sound of his favorite music. Otherwise, the reception may be completely absent.

Such consequences most often arise not only due to the great distance from radio stations, but also in a metropolis. Various types of interference are found in those receivers that operate on the FM and VHF bands. The thing is that these types of signal propagate in a special way. Their frequency does not exceed 108 MHz. Experts note the fact that all waves from this strip propagate only within the line of sight and bend extremely poorly around any hills in their path.

main parameters

Before you start making an FM antenna with your own hands, you need to carefully study the theoretical part. Each wave is broadcast on a specific carrier frequency, to which the receiver is tuned. It is for these parameters that the manufactured antenna should be designed. Of course, it will also capture other radio waves, but the final quality of their sound will be weaker.

There are certain parameters that distinguish units for the FM and VHF bands. The ultrasonic product perfectly picks up signals within a 74 MHz radius. The maximum for FM is 108 MHz. It is worth noting that modern broadcasting is practically absent on ultrasonic waves, which is why VHF antennas have gone out of popularity. That is why only FM units need to be manufactured.

The main parameter on which the efficiency of using a homemade antenna depends is the wavelength of the received signal. This indicator also affects the geometric dimensions of the device. Each master can independently calculate the wavelength, for this you need to divide the speed of light (m / s) by the frequency of the required signal. The resulting number must be translated into hertz. The final figure is obtained in meters.

All internal antenna assemblies for radio receivers and some external models are capable of picking up the signal. But there are also designs that differ in the presence of a directivity pattern; the maximum sound quality can be achieved only if the user has made fine adjustments. Such designs have a significant advantage: they are able to amplify the signal, which is unusual for non-directional models.

Sound quality is highly dependent on polarization.

All generated signals in the FM band pass vertically. The radius of the change in the field strength cannot be horizontal (relative to the direction of the main propagation). That is why a homemade antenna must be designed according to this scheme.

Varieties of the lineup

Everyone who has decided to build an antenna for FM radio with their own hands should understand that the main task of such device is to pick up the transmitted signal, amplify it and transmit it to the input of the used receiver. Depending on the required range, the final unit may differ not only in the type of construction, but also in dimensions. Experienced experts say that the modern market has a huge variety of antennas, and some of them can be safely called the most complex engineering structures that can occupy up to several thousand square meters.

In the standard model, the receiving device can be equipped with a universal conductor suspended above the ground on protective insulators. Those electromagnetic waves that cross such a unit induce an alternating high frequency voltage in it and transmit it to the input of the radio receiver. The final device amplifies the signal, due to which a specific low-frequency component is released from it, and the user himself hears a high-quality sound.

All modern types of FM setups can be divided into omnidirectional and directional. Among the masters there is a special classification by the field of purpose: mobile and stationary. Despite the huge difference in types and types, there are uniform norms by which they function.

DIY technique

Making an antenna for a radio with your own hands is not so difficult, the main thing is to prepare all the necessary materials and follow the basic rules. A significant increase in the quality and sensitivity of reception is achieved by vertical installation of the device under the range of propagation of radio waves. It takes a master from 30 minutes to 3 hours to make one unit. But to create the structure itself, you will need available items that can often be found in the garage.

Universal pipe aggregate

The basis of the structure is presented in the form of heating or indoor water pipes. The final product is extremely strong and durable. For work you need to prepare the following materials and tools:

• Quality foil of copper or brass type.
• A special ferrite core taken from a tube TV or a line transformer.
• Durable installation wire up to two meters long and 0.25 sq mm cross-section.
• Regular PVA glue, as well as sticky tape.
• To connect the antenna to the receiver itself, you will need fixing pins.

Initially, you need to take a core and make a winding for it. For these purposes, you can use not only electrical tape, but also paper, which must be laid in two even layers. One ball of foil is wrapped neatly over the paper with a slight overlap (1 cm). In the overlap area, everything must be insulated in order to prevent contact between the two sides of the winding. On the preparatory screen, the master must wind 26 turns of wire with taps for 8, 12 and 24 turns. The ends are inserted into the connecting pins. The final setting of the receiver is carried out according to the scheme for selecting the windings of the communication loop.

Indoor heating pipes will help to properly ground the FM antenna. This allows the user to count on good sound quality even during thunderstorms without the risk of damaging their equipment. It is worth noting that it is the vertical installation of pipes in a high-rise building that can amplify the signal 2-3 times.

Multifunctional foil square

Many craftsmen make such an FM antenna for a music center, since this option is not only affordable, but also effective. Moreover, the design is quite simple to implement. For work you will need:

• Strong metal foil.
• Well-dried board, chipboard or dielectric material.
• Flux, solder, soldering iron.
• A small piece of shielded cable with resistance ranging from 50 to 70 ohms.
• A regular plug for connecting to a radio receiver.

The manufacture of such a unit takes a minimum of time. Initially, the master creates a square frame from a single piece of foil, where a neat 17 mm cut is necessarily made in the lower part. The finished structure is fixed on a flat wooden base with glue. Further, the screen and the central core of the wire are soldered to the lower right and left edges.

It is worth noting that for this product it is not at all necessary to adhere to any clear parameters, the main thing is that all this is neat and of high quality. The distance between the central core and the braid should vary from 25 to 40 mm. The finished structure can be installed both indoors and outdoors. The signal can be tuned by moving the antenna exclusively in the vertical direction with smooth turns around the axis.

Original omnidirectional device

It is quite easy to design such an FM antenna with your own hands, especially if the master has a suitable coaxial cable available. The device is actively used for high-quality amplification of the radio signal in the area of ​​unstable coverage. The design consists of the following elements:

• Durable plastic tube with a diameter of 24 mm and a length of 2 meters.
• A small TV-type cable from one meter or more.
• Wooden base.

Having measured 70 cm from the beginning of the wire, the technician should make a small cut to carefully remove the plastic insulation and maintain the strength of the shield braid. When he completes this simple task, he needs to turn the shield towards the formed notch in the insulation without damaging the copper core. The antenna must be carefully positioned and fixed securely inside the plastic pipe. Further, the entire structure is attached to a previously prepared wooden mast. The planned signal adjustment can be carried out only after the finished product has been connected to the receiver and the direction of the mast height has been adjusted.

The huge advantage is that radio tuning takes place without rotating the antenna around its axis. Due to the fact that a shielded cable is present in the circuit, this helps to prevent the influence of interference that occurs during the operation of household appliances.

An indispensable design for urban environments

In a metropolis, the radio will work much better if the master uses a wave-type television antenna. Its undeniable advantage is that it is considered to be highly directional. This characteristic is especially important in urban environments, since the user can always select the radio station with the least interference.

A homemade wave-type antenna consists of an arrow with parts fixed on it - a loop vibrator, two passive directors, a reflector. The final dimensions of the product depend solely on the reception range. The very design of the antenna provides the highest quality reception at a distance of 60 km and more.

The finished design differs in that its output impedance is 75 Ohm, due to which the cable can be safely connected directly to the matching box. Depending on the preferences of the DIYer, he can use VHF TV antennas with 5 channels.

Signal attenuation reasons

Each receiver is necessarily equipped with an antenna, which helps the device to perceive the signal, separating it from interference and noise. A high-quality unit has good sensitivity to transmitted waves, but with increasing distance, the radio signal level decreases. Over a long distance, signal reception becomes simply impossible.

Even in advanced cities, there are often dead zones where the receiver does not work. And the thing is that the transmitted signal propagates in a straight line, and through obstacles (multi-storey buildings) he cannot pass. In such a situation, the signal is reflected and loses its power.

Experts say that the straightforward propagation of FM radio waves does not allow devices to normally they can also be caught beyond the horizon, where the broadcast of waves from the previous radio station simply cannot get there. The signal gets there only after reflection from the clouds, and this largely depends on the weather conditions. You can only get out of this situation by making more powerful antennas on your own.