03-13-2015, 05:34 PM
Yes, it says that the oscillator continues to operate below 700 kHz, but doesn't tell you if it is at the right freq below the 700kHz dial setting.
Turn up the time/div knob on the scope so that you can see the individual osc cycles instead of the solid RF envelope. There should be a setting ariound the knob like .5 us/div, or 500 nsec/div which will allow you to see the individual cycles and estimate their frequency. Set the scope to auto trigger so it will display the sine wave cycle waveform.
When you have the scope set up this way, as you turn down the dial on the radio you will see the spacing between cycles increase, which is telling you that the freq is decreasing. As you drop below 700 kHz, the spacing should increase smoothly with no sudden jumps. If the is a sudden change, them there is probably something going on with the tuning cap, causing a large jump in freq which would lead to noise and no reception.
Turn up the time/div knob on the scope so that you can see the individual osc cycles instead of the solid RF envelope. There should be a setting ariound the knob like .5 us/div, or 500 nsec/div which will allow you to see the individual cycles and estimate their frequency. Set the scope to auto trigger so it will display the sine wave cycle waveform.
When you have the scope set up this way, as you turn down the dial on the radio you will see the spacing between cycles increase, which is telling you that the freq is decreasing. As you drop below 700 kHz, the spacing should increase smoothly with no sudden jumps. If the is a sudden change, them there is probably something going on with the tuning cap, causing a large jump in freq which would lead to noise and no reception.
