Dividers Introduction


This phase installs the flip flop dividers, which divide the local oscillator's output into four quadrature signals, each at a frequency of exactly one-fourth the LO frequency and each 90 degrees out of phase with the other (0, 90, 180, 270):

4 divider outputs

The four divider outputs are color-coded on the schematic below, a color-coding scheme that will be used, as well, in the follow-on Mixer Phase.

These signals will be used to clock the quad bilateral switches in the mixer stage, which is closely patterned after the Tayloe detector (see discussion at page 18 of "A Software Defined Radio for the Masses, Part I"

(go directly to build notes)

Dividers Schematic


(go directly to build notes)

Dividers Bill of Materials

Stage Bill of Materials

(resistor images and color codes courtesy of WIlfried, DL5SWB's R-Color Code program)

4100 1/4W 1%br-blk-blk-blk-br br-blk-blk-blk-br1/4W
2220 1/4W 1%red-red-blk-blk-brn red-red-blk-blk-brn1/4W
110 nF (.01uF)103 103Ceramic
4100 nF104 104Ceramic
247 uH molded inductor 10%yel-vio-blk-slv yel-vio-blk-slvChoke
174AC(HC)74 Dual-D FF74HC74 or 74AC74 74HC74 or 74AC74DIP-14
1100 uF/25Vdc Electrolytic
1220 uF/16Vdc Electrolytic

Dividers Summary Build Notes

Dividers Detailed Build Notes

Top of the Board

Dividers Top View

Install Resistors

R4-1100 1/4W 1%br-blk-blk-blk-br br-blk-blk-blk-br1/4W 
R4-2100 1/4W 1%br-blk-blk-blk-br br-blk-blk-blk-br1/4W 
R4-3100 1/4W 1%br-blk-blk-blk-br br-blk-blk-blk-br1/4W 
R4-4100 1/4W 1%br-blk-blk-blk-br br-blk-blk-blk-br1/4W 
R4-5220 1/4W 1%red-red-blk-blk-brn red-red-blk-blk-brn1/4W 
R4-6220 1/4W 1%red-red-blk-blk-brn red-red-blk-blk-brn1/4W 

Install Chokes

Do not confuse with the 470 nH choke!

L4-147 uH molded inductor 10%yel-vio-blk-slv yel-vio-blk-slvChoke 
L4-247 uH molded inductor 10%yel-vio-blk-slv yel-vio-blk-slvChoke 

Install Ceramic Capacitors

Note: the 10 nF capacitor is shaded a different color and marked "103" on the board layout graphic.

C4-110 nF (.01uF)103 103Ceramic 
(just below 100 uF Electrolytic)
C4-2100 nF104 104Ceramic 
C4-3100 nF104 104Ceramic 
C4-4100 nF104 104Ceramic 
C4-5100 nF104 104Ceramic 

Install IC 74AC74PC

U4-174AC(HC)74 Dual-D FF74HC74 or 74AC74 74HC74 or 74AC74DIP-14(notch toward 100 uF electrolytic)
Take ESD precautions

Install Electolytic Capacitors

Take care to respect polarity - see board layout

C4-6100 uF/25Vdc Electrolytic 
C4-7220 uF/16Vdc Electrolytic 

Inspected Completed Board

Inspected Completed Board photo

Dividers Testing

Voltage Tests

Test Setup

Select a frequency in the oscillator and measure the voltage with respect to ground at each of the pins on IC9

Test Measurements

TestpointUnitsNominal ValueAuthor'sYours
IC9-5 (and IC9-12)Vdc2.52.5_______
IC9-3 (and IC9-11)Vdc2.52.51_______
IC9-2 (and IC9-8)Vdc2.52.42_______
IC9-1 (and IC9-4, IC9-10, IC9-13, and IC9-14)Vdc55.01_______

Check for Frequency

Test Setup

Tune HF receiver to detect the signals from the dividers by selecting one frequency of G3020 oscillator at a time. You should hear signals on (in order of selected oscillator):

  • 30m: 10.125 MHz
  • 20m: 14.045 MHz
  • 20m: 14.138 MHz
  • 20m: 14.232 MHz

You may need to use a clip lead as an "antenna", clipping it to any of pins 5, 6, 8, or 9 on the 74AC74 divider IC. Each pin has the identical signal but the signals each correspond to different phases (0, 90, 180, or 270 degrees).