Receivers of modern radio tape recorders can provide reception of transmissions of radio stations of the FM-band of informational and entertaining nature. The right choice of antenna largely determines the quality of listening to radio broadcasts in stereo. This applies both to stationary radio tape recorders and to devices mounted on vehicles. The antennas of the latter should ensure the stable operation of the radio when changing the reception conditions while driving.
Active and passive antennas
The design features of the antenna device determine the quality of the received radio signal. Active are called antennas, which include additional electronic amplifiers of the received signal. Amplification occurs by active elements - transistors. For their work requires the presence of an additional source of constant voltage. The power of the amplifiers of the stationary antennas for the radio is carried out by the voltage of the adapter included in the delivery. Car antenna antennas use the voltage of a battery or a running engine generator.
Antennas in which signal amplification is carried out only due to competent decisions of the designer during design are called passive. We can say that the active antenna device consists of a passive antenna and an amplifier that compensates for the attenuation of the signal in the antenna cable.
Stationary Receivers
Antennas for this class of receivers are made in compliance with all the rules associated with the theory of creating antenna-feeder devices. These primarily include the correspondence of the geometric dimensions of the vibrators to the length of the received wave. The ratio ¼ is selected to highlight the frequency of the radio station of interest from the ether. For the FM range, this value is 0.75 meters. The dimensions of the rooms for indoor antennas allow the use of directional structures with a high value of their own gain.
Car Antenna Options
When choosing an antenna device for the car radio, you need to decide on the method of mounting it on the car. Car antennas for the radio can be of external and internal use. Outside, the antenna can be mounted mechanically on the roof (behind the gutter) or on the rear bumper. An active quarter-wave vibrator, made in the form of a solid metal bar, ensures the best reception quality compared to other types of car antennas.
The telescopic mortise antenna allows for optimal reception of the selected station by changing the length of the vibrator. Changing the geometric size is carried out by a special engine. His work is controlled by the driver with a button inside the cabin. The presence of an additional electrical device reduces the reliability of the use of a telescopic antenna.
Using a magnet is the easiest way to mount the antenna to an external surface. In this case, the corrosion resistance of the vehicle coating is not violated. The main disadvantage is the low sensitivity of the antenna in the FM band due to the insufficient length of the main vibrator pin. All considered antennas have a circular radiation pattern and do not have selective properties. Their gain is close to unity.
In-cabin antennas for the radio are often equipped with a signal amplifier.
The overall gain of this type of antenna device is determined by the amplifier. It acts both for the wanted signal and for interference at the operating frequency. The location of the interior antennas is the windshield of the car on the passenger side. Fastening is done with double-sided adhesive tape (adhesive tape).
Antenna connection
To connect passive antenna devices to the radio, use the high-frequency connector with the designation ANT. How to connect the antenna to the radio if there is an additional signal amplifier in its composition? In the case of using a stationary receiver, power to the antenna amplifier can be supplied from the supplied adapter through the low-frequency connector on the housing of the active antenna. The antenna cable is connected to the high-frequency connector ANT of the radio.
In the absence of an additional power connector, an antenna separator or DC injector must be used. These devices allow you to use the antenna cable both to power the amplifier with direct current, and to transmit the signal of the radio station from the antenna to the receiver via the ANT connector.
A variant of the active car antenna involves the use of a car radio connector made in accordance with the ISO standard.
In this case, pin 5 of connector "A" is designed to supply the active antenna with a constant voltage of +12 V. It is necessary to connect the red (+) wire of the active antenna to it. The black wire connects to the car body at any convenient place near the antenna. The high-frequency cable is connected to the antenna input of the radio. Sometimes this may require a special adapter.
Conclusion
After reading the material presented in the article, the reader, when purchasing an antenna for the radio, will be able to make an informed choice. You can now install and connect the selected device yourself. This does not require the use of expensive appliances and tools.