• rfsniff

    From LU9DCE@21:5/101 to BBSRT on Tue Jul 2 19:40:05 2019


    +----+-----------+----------------+-------+
    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.




    --- Mystic BBS v1.12 A43 (Linux/32)
    * Origin: HAMRADIO telnet lu9dce.dynu.com (21:5/101)