Parts For Doppler-to-RS232 Interface

UPDATESemiconductors and crystal (except U2 and U3) are available as of this writing from Jameco Electronic Components, 1355 Shoreway Road, Belmont, CA 94002, phone (415) 592-8097. Jameco part numbers are shown in a separate column below. William Frovik NØMNB has reported that U2/U3 are available at Techsonic in Foster City, CA 94404, phone (415) 412-5245. More recently, Chris Stewart KE6MNR reported that Techsonic had U2 but did not have U3. He got both ICs from Atex Electronics in San Antonio, Texas, phone (877) 367-2839.


U1        74LS75                48021
U2        AY-3-1015D
U3        AY-5-8116
U4        MAX233                106163
U5        CD4024                12853
U6        74LS08                46375
U7, U8    555                   27422

C1        1 uF
C2        10 uF
C3        22 uF

R1, R5    1 K
R2        12 K
R3, R4    470 ohms
R6        47 K
R7        10K

VR1       100 K potentiometer

X1        4.9152 MHz crystal    14621

LED1, LED2  Light emitting diode

Q1        2N3904  38359
Q2        2N2907  38279

D1        1N4148

J1-3      Jumper blocks

All resistors are 1/8 watt

Blank etched circuit boards are available form FAR Circuits, 18N640 Field Court, Dundee, IL 60118 (847) 836-9148. Quoted price is $5.50 each plus $1.50 shipping (up to four boards). Add $3.00 service charge for credit card orders.

Larry WB9SDD built a beta version of this board and reports an error as follows: R7 on the board goes from pin 2 of U8 to ground. It should go from pin 2 of U8 to +5volt source per the schematic. If you order this board, check to see if this error has been corrected, and if not, make the correction with cuts and jumpers. Arnold Molloy W1GDJ notes that jumper designations A through H are not stencilled on the board. See the revised schematic for the corresponding IC pins for each jumper.

Circuit Board

The new FAR Circuits board measures 3-3/4 by 3-1/8 inches.


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This page updated 21 May 2003