Oscillator Section
We will be using the following components:
2 |
R55, R56 | 10k | resistor bag | |
2 |
R57, R60 | 499 | resistor bag | |
1 |
R58 | 1k | resistor bag | |
1 |
R54 | 10 | resistor bag | |
2 |
C50, C73 | 0.1uf | capacitor bag | |
1 |
C43 | 100pf | capacitor bag | |
1 |
C45 | 22pf | capacitor bag | |
1 |
Q13 | 2N3904 | transistor bag | |
1 |
Q14 | 2N3906 | transistor bag | |
2 |
JP1, JP2 | transistor bag | ||
2 |
X1, X2 | crystal bag |
This section needs the +5volts we just tested. After assembly we will test the section with a scope and counter. The components that are colored are in the oscillator circuit. You will have a 3 pin header for JP1. That's ok, We are going to put a wire with a loop in it to serve as a ground Connection.
If you make a mistake, we should catch it when we test. That doesn't eliminate your need to be careful though.
After assembly, your board should look like this. Notice that C44 and R59 have been omitted.
After adding the 2 chip caps, C50 and C73 the bottom of the board should look like this. Time to test.
Testing
First test is a current test. I have 12.7 volts applied to the board and it is drawing 11.4ma.
Connect your oscilloscope to the left pin of JP1. Be sure to install the jumper on JP2 to select a crystal or it won't work.
I'm showing about 4.2 volts pk-pk. You should get about the same amplitude with either crystal selected.
They both seem to be close to the desired frequency. The counter hasn't been calibrated for a while so the difference from the crystal's label may be it's calibration.
Here's what the oscillator looks like on a spectrum analyzer. Each horizontal division is 10 Mhz. The 2nd harmonic is a little over -30db down from the fundamental. The screen display is from 0-100 Mhz.
Section 2 - The oscillator section
Section 3 - The divider section
Section 4 - T4 transformer build and test
Section 5 - Installing and testing the op amps
Section 6 - Installing and testing the mixer
Section 7 - Installing and testing the transmitter op amps
Section 8 - Installing and testing the transmitter mixer