Wireless Microphone
Audio in the ISM band
Published in issue 340, February 2005
When the ISM frequency band was made available in Europe for audio applications, Circuit Design, a manufacturer of professional RF modules, decided to develop suitable high-qualitytransmitters and receivers with a wide dynamic range: these are ideal for use in wireless microphones.
The WA-TX-01 (transmitter) and WARX- 01 (receiver) modules represent a novel concept in the wireless transmission of audio signals. Thanks to low power consumption, the technology lends itself to a wide range of audio applications. The transmitter and the receiver include components such as SAW filters, SAW resonators and noise reduction ICs. Resistors:
R1 = 2kOhm2
R2,R8 = 560Ohm*
R3,R4 = 220kOhm
R5 = 4kOhm7
R6 = 47Ohm
R7 = 100kOhm
P1,P2 = 10 kOhmpreset
Capacitors:
C1,C6 = 4µF7 63V radial
C2,C7 = 100nF
C3,C5,C8 = 10µF 63V radial
C4 = 470nF
Semiconductors:
D1 = LED, 3mm, green, low current
D2 = LED, 3mm, red, low current
IC1 = WA-TX-01 (Circuit Design)
IC2 = WA-RX-01A (Circuit Design)
IC3 = TS921IN (or equivalent rail-to-rail-opamp)
Miscellaneous:
JP1 = 2-way pinheader with jumper (angled if necessary)
K1 = 3.5-mm jack socket, PCB mount (e.g. Conrad Electronics # 732893)
BT1 = battery holder for two 1.5V batteries
MIC1 = electret microphone
PCB, no. 040402-1
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Click below to download a PDF copy of this article from Elektor magazine. Please note. In view of the complexity of international markets, Elektor cannot guarantee the availability of components for this project.
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