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⬅️ Previous capture (2020-10-31)
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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.