I've been trying to build a hartley oscillator and have almost succeeded, however my calculations are off by appx 1000 relative to the measured waveform. AND the kicker is that it only works when I pull out the 1u capacitor in the tank circuit. I believe that I at least have to start it with the cap in the circuit but the waveform doesn't appear on the scope until the cap is disconnected. The scope shows a waveform of 1.6mhz while I believe its supposed to oscillate at 1.6khz. Is there a separate mode of oscillation that I am seeing? Without the cap, is it just a series RLC filter in the feedback loop only allowing amplification of the series resonant frequency?
I tapped the 100u inductor at about 40/60 and have flipped it's orientation several times to try and get the gain at an acceptable level. I modeled the resistor in the tank circuit to account for inductor resistance. I wonder if the gain just isn't quite right for the intended 1.6khz oscillation, but turns out to work for the alternate series mode of oscillation. Does anyone have any insight on what's going on here?
One final point of weirdness is that upon trying to alter the series RLC feedback path by changing the emitter bypass cap to only 1u (as well as changing the other series caps) but none of this altered the waveform shown on the scope!