There are many types of walkie-talkies, and the antennas involved are also diverse, this article will start with a brief introduction to the principle of walkie-talkies, and elaborate on the classification of walkie-talkies, working methods, antennas and other parts.
First, the classification of walkie-talkies
1. Handheld walkie-talkie
This is a kind of walkie-talkie with small size, light weight and low power, which is suitable for personal carrying, and can communicate with each other while on the move, and the communication distance can generally reach 5 kilometers in an open area without obstacles. Its power is generally not more than 4W in the UHF band and 5W in the VHF band. The aircraft is suitable for communication between mobile personnel in various occasions in close proximity.
2. Car (ship, airplane) walkie-talkie
This is a kind of wireless walkie-talkie that can be installed on vehicles, ships, airplanes and other vehicles directly powered by the power supply of the vehicle, and uses the antenna on the vehicle (ship, aircraft), mainly used for transportation, production scheduling, security command and other services. Its volume is large, the power is not less than 10W, generally 25W, and the high power is generally 50 W.
3. Analog walkie-talkie and digital walkie-talkie
In terms of design technology, radio walkie-talkies can be divided into analog walkie-talkies (also known as traditional walkie-talkies) designed with analog communication technology, and digital walkie-talkies designed with digital technology.
4. Simplex machine and duplex machine
Simplex communication means that at the same moment, information can only be transmitted in one direction, you say I listen, I say you listen. This kind of transmitting and receiving can only work alternately, and the radio walkie-talkie that cannot work at the same time is called a simplex machine. Duplex communication means that information can be transmitted in both directions at the same time, just like making a phone call, you can listen while talking, and listen while talking.
Second, the working principle of the walkie-talkie
1. Receiving part
The receiving part mixes the amplified signal from the RF with the first local oscillator signal from the phase-locked loop synthesizer circuit at the first mixer and generates the first IF signal.
The first IF signal is passed through a crystal filter to further eliminate the clutter signal of the adjacent channel. The filtered first intermediate frequency signal enters the intermediate frequency processing chip, and is mixed with the second local oscillator signal again to generate a second intermediate frequency signal, and the second intermediate frequency signal is amplified and discriminated after the useless spurious signal is filtered out by a ceramic filter, and an audio signal is generated. The audio signal is amplified through amplification, band-pass filter, de-emphasis and other circuits, and enters the volume control circuit and power amplifier to drive the speaker to get the information people need.
2. Launch part
Phase-locked loop and voltage controlled oscillator (VCO) generate the transmitted RF carrier signal, which is buffered and amplified, excitation amplified, and power amplifier to generate rated RF power, which passes through the antenna low-pass filter to suppress the harmonic components, and then transmits it through the antenna.
3. Modulation signal and modulation circuit
A person's voice is converted into an electrical signal for audio through a microphone.
4. Signaling processing
The CTCSS/CDCSS signal generated by the CPU is amplified and adjusted to the voltage-controlled oscillator for modulation. After receiving the frequency discrimination, a part of the low-frequency signal obtained by the amplification and sub-audio band-pass filter is filtered and shaped, enters the CPU, compares with the preset value, and controls the output of the audio power amplifier and the speaker. That is, if it is the same as the preset value, the speaker is turned on, and if it is different, the speaker is turned off.
3. Classification of walkie-talkie antennas
1. Vehicle antenna
The walkie-talkie and the antenna are fed through the cable, and the antenna design is related to the car shell, this kind of antenna is generally made of magnetic installation on the roof or punched hole installation, in recent years, there is a glass type or hidden in the car of this kind of antenna, the key is that the VSWR debugging and installation position directly affects the antenna radiation diagram, VSWR is generally directly related to the antenna design, cable, joint quality or bad, users should pay attention to the selection.
2. Handheld antenna
Because the line and the handset are directly fed, we call it an active antenna, the module motherboard of the antenna handset is connected with the antenna as a whole, so the motherboard module has a great influence on the antenna radiation pattern, the pattern of different motherboard modules and shell antennas is different, and the different radiation patterns make the communication quality of the walkie-talkie vary greatly.
3. Base station antenna
Generally known as outdoor antennas, this type of antenna is divided into omnidirectional antennas and directional antennas, both of which have dozens of forms and gain options. In principle, the customized antenna should be customized according to the installation environment, such as the antenna is installed on the tower, and the installation on the ground is different. Installed on a cement roof is more different from a roof with a whole roof tiled roof, so the antenna wave inclination angle is required to meet the requirements of communication distance.
1.9 GHz 3 dBi Walkie Talkie Rubber Antenna – Reverse Polarity SMA Male RF Connector
2.4-2.5 GHz/5.1-5.9 GHz 7dBi Dual Band Rugged Walkie-Talkie Antenna
Fourth, the use of walkie-talkie antenna analysis
The first thing we need to be clear about is that the higher the frequency, the shorter the wavelength, and the shorter the antenna. Usually the physical length of the walkie-talkie longer antenna gain is higher than the short antenna of the same technology, the antenna of the handheld walkie-talkie in addition to considering its own gain often has to consider the overall portability and appearance coordination, for some dual-band multi-band walkie-talkie antenna design to take into account the additional consideration of each frequency band, so often only some gain can be sacrificed.
For amateur radio enthusiasts to maximize the potential of the radio, you can make a fuss on the antenna. For example, users who prioritize ultra-portability can opt for a short stick antenna, which improves the overall portability of the radio despite the less good gain.