Experimental pulse generator.

[BillC]

I have for some time been experimenting with pulse generating circuits. This one with a 1 Meg Xtal oscillator. This circuit will produce a "comb" of harmonics to well over 100 Megs. The image shows an oscilloscope trace with about negative 6 volts in the pulse, with a rise time around 25 nano seconds as measured. Not to bad for a handfull of cheap components.

 

[BillC]

These images show a spectrum sweep of the 1 Meg. pulse generator. One sweep is from 1Meg to 150 Megs., the other sweep is from 50 to 100 Megs . The level is fairly even over a wide frequency range. This system could be used for calibration marking when tuning a receiver, or for locking an LC oscillator to any of the harmonics, the oscillator would then take on the frequency stability of the 1meg. crystal oscillator.

 

[BillC]

A bit more testing of the pulse generator and pulse transformer characteristics. Indeed it appears that my bifilar wound transformer does produce the bipolar coincident switching pulses as required to switch the diode gate. the pulse level is about 1.5 volts, good enough to switch the diodes into conduction during the sampling period of the sample and hold phase detector. The image shows the coincident switching pulses.

 

[BillC]

For members who might be interested here is the circuit for the pulse generator and VFO locking system.