RF Sniffer/BUG Detector <.5 to >500 MHz. +----+-----------+----------------+-------+ A N T + | | | | | ________ 22 --- | | | | P.B. \ | / uF --- | | | o SW 1 \|/ | | | Q2 PNP | \ | --- | / 2N | o \ | L1 GND | R5 \ 2907 | | | 4.7uH | 10K / | | +--()()()-+--/\/\/\--)--+ \ R6 E / --- | | R3 4.7K | | Q1 NPN | 4.7K |/ = B1 | D1 --- | | 2N +---/\/\/\---| --- 9VDC --- 1N270 --- C3 | | 3904 | |\ = ^ Ge | .01 / | / \ | | --- uF R4 \ | |/ | +---+ | GND 22K / +----| +----+------+ | | \ |\ | | | +-----+--/\/\/\-+ | E \ \ | | | | R1 2.2K | | | / R7 ====== | --- --- | \ --- \ 1K | BZ1| | --- --- +--->/ GND / | ~~ | | | C1 | C2 R2 \ | ====== | | .001| .01uF 10K | V LED1 | | ------+--------------+ --- >>> | | | | | | --- +-----+-----+-----+ GND | --- GND LEGEND: + = Connection ) = No Connection GND = Ground Parts List ANT = Radio Shack Cat No. ? to fit project. 24 inches or so long. B1 = Battery, 9 volt transistor radio, clip-on terminals, and mounting brkt. BZ1 = Radio Shack Cat No. 273-074 C1 = .01 uF ceramic, 50V or higher C2 = .001 uF ceramic, 50V or higher C3 = .01 uF ceramic, 50V or higher D1 = 1N270, 1N34A, or other Germanium signal diode. L1 = 4.7 uH RF Choke LED = RED LED Flashing LEDs don't need R7, and will reduce battery drain considerably. It has to be a red LED for warning! No? Well.. Q1 = 2N3904 or other NPN high gain gen'l purpose, such as PN2222A, etc. Q2 = 2N2907 or other PNP high gain gen'l purpose, such as 2N3906, etc. All resistors are 1/4 Watt unless otherwise stated. R1 = 2.2K 5% R2 = 10K trimmer pot, PCB mount R3 = 4.7K 5% R4 = 22K 5% R5 = 10K 5% R6 = 4.7K 5% R7 = 1K 5% or to suit LED brightness and battery drain. Minimum 470 ohms, except if you use a blinking LED with built-in current limiting. SW1 = Switch, SPST (single pole, single throw) push button to save bat- teries. Miniature preferred. MISC: Case, plastic. PC board to mount components on (R-S cat no. 276-148 is ok). Hookup wire, 24 gauge. Note: Keep diode and capacitor leads short to minimize stray inductance. Comments: This circuit isn't very sensitive, and could use a good wideband RF amp between the antenna and the detector diode.