SoftRock Lite - Divider

Description

The divider stage follows the oscillator. It is a dual flipflop whose whole purpose is to divide the oscillator's signal by two or four, depending on the setting of the jumper. For 40 meters we will divide by two so only half the chip is being used. To understand how it works we will use the first set on the following diagram. Each of the first three sets correspond to a flipflop. The first is the flipflop on the first chip, remember, we aren't using the second flipflop on that chip. The second and third sets correspond to the flipflops on the second chip.

In each set the first line is the clock input and the second the data input. The third line, Q, is the output and the fourth line, /Q, is the inverse of the third line. Every time the clock signal rises it takes the value (high or low) from the data signal and outputs it to Q and outputs its inverse to /Q. To make the flipflop a divider, you feed /Q into the data input. Assume /Q is low to start with. When the frequency rises the flipflop read the data input, which is /Q and low, so will output low to Q. That of course forces /Q to high. Next time the clock signal rises the data signal is high so it sets Q to high forcing /Q to low, and so forth. So what you end up with is that every rise in the clock signal will send the output signal either up or down so the output is at half the frequency of the clock signal.

Components - orange on schematic

• U2 - 74HC74, dual flipflop on the top of the board
• jumper wire set to 4x not 8x.

Only the front of the board has had components added, U2, which is the first flipflop and just above it to the left, above the letters x4 is a jumper wire.

Test

Once again this stage can be tested using the Grundig Yachtboy 400. Tune the radio to half what it was before around 14.112 MHz (28.224 / 2) and apply power to the Softrock Lite. You should hear the oscillator plainly. You can remove the power, then apply it again to confirm that it is the Softrock that you hear.

When I attached the battery I immediately heard the tone at 14.112 on the Grundig.