FM FM transmitter, transmitting frequency in the analog broadcast band 88~108Mhz, received by ordinary FM radio, 2 kinds of audio input, MIC head will send peripheral sound, CK audio input, adjust adjustable transmit coil L can change (fine tuning) launch frequency. As shown in the figure, the schematic diagram of the wireless transmitter is shown in the figure. Q1 is a common-emitter transformer-coupled oscillating circuit: the load is the è¡©-stage coil of the transformer T. After the collector output signal is coupled by T, the secondary pole is sent to the base via C1 to form a positive Feedback, start up. The base is simultaneously supplied with a low frequency modulation signal to amplitude modulate the generated high frequency oscillation. Q2 is the buffer amplifier stage. The output of Q1 is coupled to the base of Q2 ("Q1" on the right side of the figure) via C3. L1 is the load inductance of Q2; and is sent to the antenna for transmission via the C4/L2 series resonant circuit. R2 is grounded, that is, zero-biased. Because the input signal has a large amplitude and is selected by the C4/L2 resonant circuit, it is not afraid of distortion, so the efficiency is high. There should be a connection point at T, L1 and 9V. This circuit works in Class C amplification because the base has no DC offset. The phase between the primary and secondary of T is reversed, that is, when the collector current of Q1 increases, the primary induced electromotive force of T is right and left negative, and the secondary produces a positive electromotive force with left and right negative, and the charging current for C1 increases. The opposite is true when the collector current is reduced. The frequency is determined by the capacity of C1 and the inductance of T. Transmitting power Now these parameters cannot be determined. The voltage knows that the key is that the current is unknown. The current (AC current) is determined by the current of Q2 (the rear transistor should be Q2), the driving of the base, and the impedance of L1. Speaking of the receiving distance, and the receiver sensitivity, propagation environment, antenna height, antenna gain, generally speaking is also the ideal distance, the actual distance is still a big difference. The basic principle of the two circuits is the same, and the circuit is controlled by the 0 and 1 signals to realize the high-frequency pulse emission. The working frequency is determined by the crystal oscillator, and the stability is not good or bad. Figure 2 is simple and easy to debug. Figure 1 adds a frequency-selective network between the collector and the power supply of the triode. A frequency-selective network is added between the collector and the antenna of the triode. The output frequency is purer, but debugging is more troublesome. . Another difference is that the base of the upper triode in Figure 2 introduces AC negative feedback through the resistor. In fact, the effect on the stability of the circuit is not obvious. The high frequency capacitance to ground on the power supply is still good, but it is not shown in Figure 2. Screen Resolution office projector,projector for office use,projector at office depot,home office projector,hd office projector Shenzhen Happybate Trading Co.,LTD , https://www.happybateprojector.com
There are generally three screen resolutions for office projectors:
One is a 4:3 screen suitable for office PPT playback. The first is the SVGA machine with the lowest price and the highest cost performance. This kind of machine is generally priced at around 2500 and has powerful performance. The disadvantage is that the resolution is 800X600, which is relatively low. The second is the XGA machine, which is an upgraded version of the SVGA machine with a resolution of 1024X768.
The other is the 16:10 aspect ratio screen used by some foreign-funded enterprises, which is the 1280X800 resolution of WXGA. However, with the transparent price of 1080p projectors, more and more companies will choose full HD 1080p projectors as their office projection solutions.
Office Projector Features
According to the needs of different office environments, office projectors are roughly divided into three categories.
One is a conventional projector that is placed or hoisted in the conference room, the second is a Portable Projector that can be carried around, and the third is an ultra-short-throw projector that is convenient for work reports and speeches.
Wireless Office Projector
With the advent of the Internet era, the emergence of a series of wireless office series has added new members to the office projectors. The wireless office projector is realized by the built-in wireless module of the ordinary office projector. Wireless office makes people do not need to switch signal lines frequently in office meetings, allowing people to have a better experience in meetings!