D5W 76-108MHz 500mW FM radio Transmitter-2000m FM and stereo transmitter with digital display.

Power supply requirements: 

0.5W FM radio transmitter uses USB Type C interface for power supply, with power supply voltage of 5V and consumption current of no more than 500mA. 

Input audio signal: 

3.5mm stereo audio socket,3.5mm male audio cable is required. 

Transmitting interface: 

The transmitter side is SMA female head with external thread and internal hole. SMA male head and signal wire of internal thread shall be used for connection. The characteristic impedance of the signal line is required to be 50 ohms, Teflon material is recommended, the recommended specification is 50-3, and the line length is not less than 2 meters. 

Antenna requirements: 

the working frequency should be 50 ohm pure resistive load, and the VSWR should not be higher than 1.5. 

Note: Since the transmitter's transmission power is 0.5W, the transmitter will not be damaged in the total reflection state, so the requirements for the antenna are not high. The more qualified the antenna is, the farther the transmission distance is.

Description of operation sequence: 

1. Connected to antenna 

2. Connected to power supply 

3. Connected to audio input

Panel description: 

The panel includes the following factors: 

LCD display window 

Key 

Red LED indicator 

Top SMA interface antenna base 

Top audio input socket 

USB-C power socket.

KEYS: 

DW (step): 

The default state is to lower the frequency (DW) and step to 0.1MHz. When the frequency drops to 76MHz, it will automatically cycle to 108MHz. 

Press and hold the DW key for 3 seconds to switch to 1MHz step and the LED is on for a long time. 

Press and hold the DW key for 3 seconds again to switch back to 0.1MHz step and the LED is off. 

UP (res): 

The default state is up regulation (UP) and the step is 0.1MHz. When the frequency rises to 108MHz, it will automatically cycle to 76MHz. 

Frequency reset: 

press and hold the res key for 3 seconds, and the output frequency will automatically return to 90.00MHz. Each time you press the key, the LED will flash. Five seconds after the operation of all buttons is stopped, the led flashes, the machine saves the current working frequency, and the next time the machine is powered on, it will automatically work at the saved frequency. 

Audio input: 

The input audio volume should be adjusted according to the radio reception effect, so that the sound is clear without distortion. 

Power input: 

5V power supply, the maximum is not more than 5.5V. If the maximum working voltage is exceeded, the transmitter may be damaged.

Use a mobile phone charger with a USB type-c charging cable. The charger should try to use products with low ripple and low noise, so that the output signal quality of the transmitter is better. 

Antenna:

The antenna should use a GP antenna (umbrella antenna), a 50 ohm coaxial line above 2 meters, and be connected to the transmitter using SMA male. Theoretically, the thicker the feeder, the better. The 50-3 specification is recommended as a compromise. VSWR should not be higher than 1.5. A good antenna helps to increase the transmission distance. Under ideal conditions, a pair of adjusted antennas can transmit a distance of 2000 meters. Of course, a pair of antenna that has not been debugged or has not been debugged well, the transmission effect is disastrous, which may be only a few hundred meters, or even tens of meters!

Antenna knowledge 

An antenna is an open device that emits electromagnetic waves. Its operating frequency is determined by the structure and size of the antenna. 

Common GP antennas can provide limited available bandwidth. For example, my hand made antenna has the lowest reflection coefficient (- 20dB) at 88.3～91.3MHz, and can provide standing wave of no more than 1.2 in this frequency range. When our transmitter works with this antenna, we should keep the working frequency in the range of 88.3～91.3MHz. In this way, the best launch distance can be obtained. 

Actual erected antenna: 

The vibrator adopts 2mm thick copper wire, which can be replaced by other conductors. Variable length materials such as rod antennas shall not be used for antennas. If you need to use it permanently, please take waterproof and lightning protection measures to ensure safety!