Quartz Oscillator 13560 kHz Description Transistors are german small plastic lo-power npn-HF-types. If you do not get BF 494, please try 2N2222A or similar types, but you may have to change other things, like resistors and capacities, as well. I did not try 2N2222A. Transistor T1 works as a colpitts oscillator. The coil L1 and the capacitor C5 should be tuned to 13560 kHz. The capacitor C3 produces the in-phase feedback. Signal from collector (output) goes through C3 to the emitter (input of transistor T1). In principle, in order to get oscillation, the base of the transistor has to be be connected to ground for the RF signal. This is done by the quartz Q. The small capacitors C1 and C2 are necessary to adjust the exact frequency of the quartz. If you are happy to get a very accurate quartz, then C1 should be approx. 90 pF, and C2 can be abolished. But, if the quartz is as incorrect as it usually is, you have to shift the frequency a bit up or down. You need the adjustable C1 in order to get a higher frequency by deminishing the capacity of C1. Using increasing capacity of C2, you may tune the quartz to lower frequencies. Adjustment range may be 500 Hz up and down, not more. Please do not use low capacity of C1 together with high capacity of C2. Either oscillations may disappear, or you will get wild oscillations. You may find it funny that we pick up the signal from the emitter of T1, the emitter being the input of T1 in this case. The reason is, whatever you may connect to T1: everything will change the frequency. This influence is minimum using the emitter. Capacitors C7 and C8 together with resistor R4 will work like a lowpass filter to suppress the second and third harmonic. TP1 may be used to connect your oscilloscope. Transistor T2 buffers the signal and reduces influence of connections which you make to the output of the oscillator. R11 together with C13 have a lowpass function. Again, second order and third order harmonics are diminished. Near to the output, L2 and C16 again work as lowpass filter. The second order harmonic (27120 kHz) is diminished by approx. 20 dB due to this last filter. Connecting TP2 to your oscilloscope, you may find a nearly perfect sinusoidal wave. The IC 78L06 stabilizes the supply voltage to 6 Volts. Constant power supply renders less drift of frequency. Adjustment Sorry, I don’t think it is easy to adjust this thing without an oscilloscope. You want to know whether you get the right signal. Any quartz may oscillate on the three-fold frequency (which is 40.68 MHz in this case), or even on the five-fold frequency (67.8 MHz). First you put C1 to maximum capacity and leave out C2 (or put it to lowermost capacity). Using TP1, you may change L1 / C5 until there are broad, inverted-U-shaped pulses with a frequency very near to 13 560 000 Hz (+ - 500 Hz). Afterwards, you may adjust C1 if frequency is still to low, or you may have to add C2 in order to achieve the right frequency. If you don’t have a frequency counter with high resolution up to +/-1 Hz, you may use an accurate PLL tuner receiver with BFO. With the oscillator running, with the radio tuned to 13 560 kHz and USB reception switched on, you may listen to the interference. The higher the tone you hear, the more discrepancy between the two frequencies of the receiver and the oscillator. Then you can tune C1 and/or C2 to zero beat. Please allow some 20 minutes for warmup of the oscillator and the PLL receiver. The accuracy of this calibration depends on the accuracy of your radio. With my Grundig sattelit 700 accuracy was about +/-35 Hz. This means that with this type of calibration the real frequency of the oscillator differs from 13560000 Hz by only 35 Hz. Higher accuracy is possible with more exactly calibrated equipment. Using a DDS generator ("direct digital synthesis") which was running more than 2 hours for warmup, accuracy was about +/- 10 Hz. (By the way, temperature dependent change of frequency was +/-10 Hz between 15 degrees C and 25 degrees C. This temperature dependent change is non-linear: The temperature-frequency-curve is s-shaped. Change of frequency is max. 5 Hz per degree temparature change. Highest stability was measured in between 20 degrees and 21.5 degrees C. These temperature properties are mainly due to the temperature dependent data of the quartz.) Afterwards, you connect your oscilloscope to TP2. You should adjust L2 until there is a perfect sinusoidal wave. Are you sure that there are no second order harmonics? If you just see the sinusoidal wave on the screen of your scope, you are not. If you want, you may use a filter to separatly display the harmonics on your oscilloscope sreen (see fig. filter to visualize harmonics). Just connect the filter to the oscillator output. After connecting your oscilloscope to the filter, you may find the 13 560 kHz signal attenuated on the scope, and now you may be able to see the second order (27120 kHz) or higher order harmonic signal on the scope. Then, adjust L2 again, until the 27120 kHz signal disappears. In the end, please remove the filter, of course.