Dividers Introduction


This phase installs the flip flop dividers, which divide the local oscillator's 28.188 MHz output into four quadrature signals, each at a frequency of 7.470 MHz and each 90 degrees out of phase with the other (0, 90, 180, 270).

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"

Dividers Schematic


Dividers Bill of Materials

Stage Bill of Materials

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

210 k 1/4W 1%br-blk-blk-r-br br-blk-blk-r-br1/4W  Dividers
4100 1/4W 1%br-blk-blk-blk-br br-blk-blk-blk-br1/4W  Dividers
110 nF (.01uF)103 103Ceramic  Dividers
2100 nF104 104ceramic  Dividers
174AC(HC)74 Dual-D FF74HC74 or 74AC74 74HC74 or 74AC74DIP-14  Dividers

Dividers Summary Build Notes

Dividers Detailed Build Notes

Top of the Board

Dividers Top View

Install All Divider Components

Be sure to orient the IC correctly (notch to the left). Also, make sure you have installed the 100 nF capacitor (above the IC), which couples the local oscillator signal into the divider stage.

E22810 nF (.01uF)103 103Ceramic 
E44100 nF104 104ceramic 
E83100 nF104 104ceramic 
E8974AC(HC)74 Dual-D FF74HC74 or 74AC74 74HC74 or 74AC74DIP-14 
Take ESD precautions
E126100 1/4W 1%br-blk-blk-blk-br br-blk-blk-blk-br1/4W 
E139100 1/4W 1%br-blk-blk-blk-br br-blk-blk-blk-br1/4W 
E94100 1/4W 1%br-blk-blk-blk-br br-blk-blk-blk-br1/4W 
R12100 1/4W 1%br-blk-blk-blk-br br-blk-blk-blk-br1/4W 
R9610 k 1/4W 1%br-blk-blk-r-br br-blk-blk-r-br1/4W 
R9710 k 1/4W 1%br-blk-blk-r-br br-blk-blk-r-br1/4W 

Dividers Testing

IC Voltages

Test Setup

Power ON and measure voltages (with respect to ground) at pins of the 74AC(HC)74 Dual-D FF IC

Test Measurements

TestpointUnitsNominal ValueAuthor'sYours
Pins 1, 4, 10, 13, and 14Vdc+5 (Vdd)+5.02_______
pin 7Vdc00_______
Pins 2, 5, 6, 8, 9, and 12Vdc+2.5+2.49_______
Pins 3 and 11Vdc+2.5+2.52_______

Frequency Test

Test Setup

You can use an HF receiver tuned to 7.047 MHz to see if you detect the signals from the Dividers.

Test Measurements

TestpointUnitsNominal ValueAuthor'sYours
Nearby receiver tuned to 7.047 MHz receives signalY/NYesYes_______

Frequency Test With Scope/Counter

Test Setup

If you have a scope or frequency counter, you can test the operation of the divider sub-phase:

  • Powering up the board at 12 Vdc
  • Probe each of the four pins: 5, 6, 8, and 9 on the 74AC74 chip.
  • Each pin should register a frequency near 28.188/4=7.047 MHz.
  • The wave forms should resemble those shown on the Mixer Schematic

Test Measurements

TestpointUnitsNominal ValueAuthor'sYours
pin 5MHZ7.047 (square)7.047 (square)_______
pin 6MHZ7.047 (square)7.047 (square)_______
pin 8MHZ7.047 (square)7.047 (square)_______
pin 9MHZ7.047 (square)7.047 (square)_______