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http://web.telia.com /~u43200663/tx/fct-bug.htni

SINGLE FET VHF (88-108 MHz) FM WIRELESS MIC by Frank v H ..

SINGLE FET VHF (88-108

MHz)

FM WIRELESS MIC

by Frank v Hughes

The circuit shown depicts a wide band FM wireless microphone. Its power and rangę are similar to the commonly known circuits. which use bipolar transistors. The simplicity of the design means it is certain to work Firsl time. One gate circuit ofthe MOSFET is a self excited RF oscillator, and the other gate circuit acts to bias the device and also as a microphone pre-amp and modulator.

+ 9V — — —

	• ^G1	n\
	G2	LI	fc

SINGLE FET VHFFM ‘BUG*

88 -108 MHZ

FRANK HUGHES VK6FH

Tl Bose Diag 40672,BF900 or sim' Mosfet

ANT

Tuning can be eflected by rnaking Ct a trimmer padder capacitor, or altematively ifthis is a fixed value, then expanding compressing the coil should give sonie \ ariation in frequency. Almost any dual-gate N-Chaiuiel MOSFET should work; suitable types are 40673. 40822. BF900. BF988 . A 9V battery is used as a power supply. The rangę could be increased by adding a PA stage as shown on the FM bug V5 (SMOYPOweb pągęs).

If you have any questions related to this project then please refer them to the autlior Frank V. Ihmhes.

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2008-11-17 19 40