Radio working principle
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Radio working principle

2012-7-4 10:20:33 reading: 254

In 1, transmitting part:

Phase locked loop and voltage controlled oscillator ( VCO ) generates and emits a radio frequency carrier signals, through a buffer amplifier, exciting amplification, power amplifier, produce rated power, through the antenna low pass filter, harmonic component, and then transmitted through an antenna.

In 2, receiving part:

The receiving part is two superheterodyne, from the antenna input signal through the transceiver conversion circuit and a band pass filter after RF amplification, after band-pass filter, into a mixer, will come from the RF amplification signal from the PLL frequency synthesizer circuit of the first local oscillator signal in a first mixer at mixing and generate first intermediate frequency signal. The first intermediate frequency signal through the crystal filter to further eliminate the clutter adjacent channel signal. The filtered first IF signal into the intermediate frequency processing chip, and the second local oscillator signal again mixing generates a second intermediate frequency signal, a second intermediate frequency signal through a ceramic filter to filter out unwanted spurious signal, amplified and frequency, audio signal. Audio signal through the amplification, band-pass filter, de-emphasis circuit, into the volume control circuit and power amplifier, speaker, get the information people need.

3, modulation and modulation circuit:

Human voice by microphone converts audio signals, the audio signal by amplifying circuit, pre-emphasis circuit and band-pass filter into the voltage controlled oscillator direct modulation.

In 4, signaling processing:

CPU CTCSS/DTCSS signal after amplification adjustment, into a voltage controlled oscillator modulation. Receiving frequency is low frequency signal, one part after amplification and sub audio band pass filter shaping, enter the CPU, and the preset value, the control of audio power amplifier and loudspeaker output. If the same is opened and the preset value, the speaker, if different, then close the speaker.

Use the interphone will not have radiation? Interphone design in line with the Ministry of information industry [2001]869 document of the relevant provisions, will not harm the human body, and use the interphone is not close to the human communication, but the human body 5 to 7 cm distance call.

Influence of the intercom distance and effect factors has the following several aspects:

1, the system parameters:

1) the output power of the transmitter is more strong, emission signal cover range bigger, the farther communication distance. But the transmit power is not too large, the transmit power is too large, not only power, influence power amplifier element, and interference is strong, influence others talking effect, also will produce the radiation pollution. National Radio Management Institution of communication equipment transmitting power are clearly defined.

2) communication receiver sensitivity is high, the communication distance is farther.

3) the gain of the antenna, the antenna and machine matching, usually, antenna height increases, receiving or transmitting ability enhancement. Walkie talkie antenna generally used for spiral antenna, the gain and bandwidth than other kinds of antenna to smaller, more easily affected by a human body.

2, environmental factors:

Environmental factors are the main path, tree density, electromagnetic interference, building environment, weather and terrain. These factors and some other parameters directly influence the signal field strength and coverage.

In 3, the other influence factors:

1) a low battery, when the battery power is low, the call quality will become worse. When severe, there will be noise appear, affect the normal call.

2) antenna, antenna frequency band and machine band discordance, antenna impedance matching, will seriously affect the communication distance. For users, for use when the antenna must pay attention to the antenna to tighten, also cannot use the manufacturers to provide antenna, also cannot use does not conform to the machine frequency antenna.

3) quality depend on pre-emphasis and de-emphasis circuit, there are currently more advanced speech processing circuit " speech compression and expansion circuit and low expansion circuit applications ", the fidelity voice has a very good effect.

4) influence the intercom distance and effect factors are associated with seasonal, summer than winter.

Radio host including which main components?

In 1, shell:

Professional machine generally adopts the plastic material with good performance in PC+ABS, appearance gloss good, not easy to aging, wear, durable products; commercial machine is often used in engineering plastics ABS, in appearance, strength, wear resistance, aging and so on can well meet the requirements; keys using silica gel, wear resistance, not easy to aging, feel good; aluminum shell made of light material of aluminum alloy ADC12, easy molding and follow-up processing.

In 2, the host:

Generally comprises a face shell, PTT keys, headphones and plug the hole plug, PCB component, part LCD, volume / switch button, coding, indicating lamp, MIC knob. The PTT key on emission of switching function, generally on the side. Indicating lamp indicates the work state, usually at the top of. Radio top volume / switch and a code knob ( select channel ). Part LCD visual display walkie-talkie working state. PCB component is the core part of the walkie-talkie, important devices in PCB, non-professionals to remove. Most walkie-talkies for technical performance and resistance to breaking characteristic, there are special shielding enclosures, aluminum shell ( PCB fixation ). Professional machine and the waterproof requirement, the structure of more complex.

In 3, the battery:

Battery Ni-Cd, Ni-MH cells and Li-ion cells, has a capacity of 600mAh, 800 mAh, 1100 mAh, 1500 mAh range. Lithium battery cost is expensive, is still in the development stage. Ni-Cd and Ni-MH battery use is more widespread, generally large capacity battery recommended by Ni-MH battery. Cell surface, a bottom shell using ultrasonic welding, firm and reliable.

In 4, the belt clip:

The role of the walkie-talkie fixed on the belt, in order to customer convenience, detachable belt clip.

5, antenna:

Antenna and antenna core is divided into two parts. Antenna jacket with a high performance TPU material, the bending resistant and anti-aging performance; the antenna core general use the thread structure is connected with a host machine, convenient disassembly.

6, htc:

And adaptors common battery or charging machine. The general structure of a DC socket, charging elastic plate, lights, buttons and other. DC socket and adaptors connected, shrapnel and battery pole piece connected, indicator indicates charging status, the key is the discharge effect. Charger of battery charging and the general.

7, in addition, walkie-talkie and holster, headphones and other ancillary products

Purchase walkie-talkie need which to go through formalities?

The use of wireless walkie-talkie to occupation of frequency resources, so we must apply to local radio management committee to appoint approval, no use of purchase, need to handle the specific procedures are as follows:

1, to appoint or distributors for " set the radio returns ";

2, fill out the form, use the area, purchase quantity, use must be filled out clearly and stamped with the official seal units;

In 3, a return to the district Secrets Bureau ( usually in the district government agencies within the ) registration, district Secrets Bureau approval, sign the application form and will form returned to the applicant;

In 4, holding the " application form " to appoint declare. No Commission approved and issued to the applicant after reply frequency of use, " purchase permit ",

In 5, a " purchase permit " purchase walkie-talkie;

In 6, a walkie-talkie and " purchase permit receipt " to appoint inspection and pay the frequency occupation fee ( per 100 yuan ). No commission issued " the radio station license ".

The use of public radio, does not need to be licensed, waiving the frequency occupation fee. The use of ( or unit ) in the purchase of public radio, fill in by the manufacturers to provide the " registration card can be ".

Use the walkie-talkie why frequency limit?

To ensure that the vast majority of users call undisturbed and reasonable use of frequency resources, National Radio Management Committee on the frequency of use were divided, different industries using the corresponding frequency range. When the user is buying the walkie-talkie, to local radio management committee for frequency point.

What is public radio?

Public Radio refers to: transmit power is less than 0.5W, working in the specified frequency wireless interphone, the radio frequency RF technology, power indicator shall meet the following requirements:

In 1, operating frequency ( .9000; 409 units: MHz ): 409.7500, 409.7625, 409.7750, 409.7875, 409.8000, 409.8125, 409.8250, 409.8375, 409.8500, 409.8625, 409.8750, 409.8875, 4099125, 409.9250, 409.9375, 409.9500, 409.9625, 409.9750, 409.9875;

2, modulation mode: F3E;

3, effective radiated power ( EIRP ): 0.5W;

4, emission frequency tolerance: <+5ppm;

In 5, the transmitter spurious radiation: <50uW;

In 6, receiver spurious radiation: <20nW;

In 7, the channel interval: 12.50kHz.

Use the intercom to pay?

Conventional radio calls without paying. No matter how frequently you use, you only need a year for each of the walkie-talkie to pay a few yuan frequency occupation fee, such as the use of public radio, do not need to pay any costs

Consumers can buy the walkie-talkie?

Conventional walkie-talkie call general distance 3~5 km, but there are tall buildings or mountains block the case, calling distance will be relatively short. When a network support, walkie-talkie call range up to several tens of kilometers.

In the mobile phone are very popular today, why people will choose to use the walkie-talkie?

This is because the interphone and mobile phone has many unique places:

1, speaking machine without network restrictions, the network does not cover the local intercom, allows users to easily communicate;

2, speaking machine offers one to one, one to many communication methods, according to said, simple operation, to communicate more freely, especially emergency scheduling and collective situations, these features are very important;

3, low cost communication.

Walkie talkie main application areas in which?

Walkie talkie mainly used in public security, civil aviation, transportation, water conservancy, railway, construction, manufacturing, service industries, for group members contact and command scheduling, in order to improve the communication efficiency and improve the quick response ability of dealing with emergencies. With the interphone enter civil market, people travel, shopping is also increasingly use the walkie-talkie.

Technical terms

Monitor ( MONITOR )

For weak signal and uses a listening mode. By special key forced on channel of a received signal, the ear to distinguish the speaker in a weak voice, to listen to.

Scan ( SCAN )

In order to hear all channel call, and the use of a listening mode. By special key, so that the receiving circuit according to a certain order of one channel to receive a period of time, in order to receive channel signal. If each channel reception time is 100ms, then the second can be scanned in ten channels, namely the scanning speed is 10ch/s.

Priority channel scan ( Priority Channel Scan )

In the process of scanning, scan priority set the priority channel.

Delete / Add Scan Channel ( Delete/Add Scan Channel )

A channel from the scan list to delete or add to the scan list.

Voice ( VOX )

When the function is activated, do not have to press the PTT key, can be directly through the phonological priming launch operation.

Emission limit ( TOT: Time Out Timer ) function

The function used to restrict users in a channel on the ultra time emission, but also avoid the interphone for long time emission and damage.

Power function ( Battery Save )

In order to save electricity, prolonging the standby time, walkie-talkie over a period of time without transmitting receiving and key operation, will be for a long time off, for a period of time starting work the way, this way is called a power-saving mode. Switch machine time length ratio is about 1:4. When a signal is received or a button, intercom immediately exit of the power saving state, into the normal state.

Low power selection function ( High/Low power )

This feature allows the user to choose according to the actual situation of high power and low power.

Lockout function (Busy Channel Lockout )

When using this function, the user is prohibited in the busy channel transmitting signals.

Squelch series ( Squelch Level )

The received signal strength and noise signal strength of a corresponding relation, the stronger the signal noise is weak. The maximum and minimum noise between divided into several files, each file called a. Into gear called squelch series. The user can choose according to the actual situation.

The CTCSS/CDCSS function

Use this function to avoid receiving unrelated call.

2-TONE/DTMF selective calling function

Using 2-TONE or DTMF signaling to select corresponding intercom call.

Reverse frequency ( Reverse Frequency )

The use of reverse frequency, radio frequency of transmit and receive frequency will be interchangeable, and the signaling also exchange.

Online function ( Talk Around )

The use of off-network function, radio emission and receiving frequency frequency becomes the same; signalling also turned and signal receiving the same.

Automatic answering function ( Auto-Transpond )

When the intercom receiving a correct code call, to send a signal to the calling party in response to a call.

Emergency alarm ( Emergency Alarm )

Press the alarm special keys, walkie-talkie to maximum sound alarm sound or send out alarm code to other handset or base station.

Patrol record (Patrol Record )

Patrol officers to patrol point, interphone will receive patrol register issued the query signal, and then automatically start the registration operation, put their own identity and other information sent to patrol the register register, indicating some patrol officers arrived in the land.

Lock function keys ( Keylock )

Use the function keys can prevent misoperation.

Battery indicator ( Battery Indicator )

Show the battery.

Lighting function ( Backlight )

Used in night or dark condition, can see the LCD display and keyboard.

Copy function ( Cloning )

This feature allows a radio data copied to other models of the same radio.

Modulation

The modulation signal with one or several