Pop Noise

Although the LA47536 includes an pop noise prevention circuit, pop noise can be reduced even further by using the muting function as well. 

Activate the muting function at the same time as power is applied. Then, after the output DC potential has stabilized, turn off the muting function. 

When turning the amplifier off, first turn on the muting function and then turn off the power supply. These two methods are effective at minimizing pop noise.

USB Mono Transmitter

This small FM transmitter with a range of about 50 meters designed for connection to the USB port. With lots of mini-transmitters then you have a comprehensive, action-packed radio program. Due to the power supply via the USB port of a high frequency stability is achieved. Alternatively, the receiver, a battery 5 to 12 volts to operate

FM Transmitter Construction 

USB FM Transmitter Prototype It is not necessary to drill the transmitter PCB. 

All components will be soldered to the plate with their legs folded, like this: 

The two transistors and the LEDs are polarized: 

The transistor has a flat side, the LED a foot longer than the other is the anode (A), the other is the cathode (K). The audio cable (minijack) must be transformed from a stereo cable into a cable. 

Booster 100 Watt FM transmitter 2011

I did some changes like in the buffer 2SC2053 just replace the resistor for the bias voltage. Section final with a 2SC1971 2SC2053 replaced. With this change the RF output generated around 3 watts. While the RF Power Amplifier using 2SC1946A 2SC1971 and 2SC2782 replaced. With this PA RF output power can reach more than 100 watts at 15 volts DC voltage. Total currents measured on the structure of this transmitter circuit at 14 amps DC.

Seen here that the PA board (2SC2782 & 2SC1946A) had burns on his part due to the PCB track-tuned and miss my plate and replace it with copper wire. PA RF PCB should use materials from fiber 2 sides (double layer) and each point / hole on the line intended to connect the top and bottom. Use copper wire that is less than 1mm and in-solder the top and bottom, see figure PCB layout and arrangement of components in the image below.

L165 symmetrical power supply

The compact 5 pin IC L165 general symmetrical a stabilized power supply from a single asymmetrical power supply. The output voltage is however, half of the input voltage. One needs to add the ripple filter capacitors C1, C2, C3 and C4 and some resistors for setting the symmetry. In constructing the circuit, place the capacitors C1 and C2 as close to the IC as possible.

On the other hand, place the capacitors C3 and C4 close to the output jacks. Make sure That the circuit lines on the pcb are properly dimensioned to handle the high current levels. Current levels up to 3 amperes can flow through the circuit. Additionally, Provide a proper heatsink for the L165 IC.

The L165 IC can also be viewed as a voltage amplifier. It amplifies the voltage Appearing at the junction of the between R1 and R2.

One cas also replace the IC with TCA1365. However, using the TCA Pls IC, pins 3 and 4 have to be connected together. Also connect a 220pF capacitor the between pins 5 and 6.

USB FM transmitter PCB Layout

The PCB designed uses resistors and capacitors with 0805 SMD packaging. The size of the board is only 41.2 x 17.9 mm, which is practically dongle-sized. For the aerial an almost straight copper track has been placed at the edge of the board. In practice we achieved a range of about 6 metres (18 feet) with this fm transmitter usb. There is also room for a 5-way SIL header on the board. Here we find the inputs to the 3.5 mm jack plug, the input to P1 and the supply voltage. The latter permits the circuit to be powered independently from the mains supply, via for example three AA batteries or a Lithium button cell. Inductor L1 in the prototype is a type made by Murata that has a fairly high Q factor: minimum 60 at 100 MHz.

Take care when you solder filter choke L2, since the connections on both sides are very close together. The supply voltage is connected to this, so make sure that you don’t short out the USB supply! Use a resistance meter to check that there is no short between the two supply connectors before connecting the circuit to a USB port on a computer or to the batteries.

Network topology

The figure above shows the network wire RS-485 2. With this configuration, apply the half-duplex communication, two-way alternate. Master for he who initiate the communication, will be the first to connect the transmitter to its network, while the slave will connect the receivers. 

Each slave will have the ID / unique address. Slave to the destination ID will then be mengaktidkan its transmitter when it will mereply permaintaan from the master. While the master will enable the receivers. Another slave who can only "listen"

In the system 4 wire, Master Transmitter connected to all slave receivers, while the receiver is connected to all the slave transmitter. In this system, the master transmitter can always be online to the network, because with four wire system, the communication can be run full-duplex, 2-way full. While the slave transmitters will only connect when there is a request from the master. The disadvantage of this system is the cable required two times more. Therefore, the network system with a distance which is much cheaper when using a 2 wire system.

FM Transmitter 88

This FM transmitter can work from a range of 88MHz to 108MHz. This transmitter circuit using a transistor 2SC1971 final transmitter. Which has been modulated RF signal in the transmitter circuit is confirmed in three levels namely first starts boosted by the amplifier transistor 2SC2053 is then strengthened again by the first amplifier transistor 2SC1970 and finally confirmed by an amplifier transistor 2SC1971. FM trnsmitter this series can be directly given input signal in the form of an audio signal. Transmitter circuit is working with the source voltage to the 12VDC and 9VDC trnsmitternya to bgin oscilator and mixernya. Transmitter circuit in this article are mono FM transmitter and is often used by hobiest and amateur radio. The circuit details of this transmitter can be seen in the following figure. 

Transmitter operating frequency can be set using the potential of 88MH 5K meters - 108MHz. Oscillator circuit is applied to the transmitter uses a system of VCO (Voltage Control Oscilator) made with diodes varaktor. Transmitter circuit are complete with pictures supplynya ehingga power circuit can be understood with less ease.