Oscillator output

[f4cepl4nt]

Just a quick question or two.... does the sine wave output of a hartley oscillator (or colpitts or another sinusoidal output oscillator) create AC (does the output voltage go negative)? Or is it just DC with voltage moving smoothly up and down?

Also, if I were to take a 1MHz signal from a square wave generator, (a 555 timer or another oscillator that just makes a pulsed DC output) , and transmit that with an EM wave;  if I had a series LC filter on the receiving end would that properly pass a square wave(or at least pass a sinusoidal component of that square wave)?

Thanks again...had a hard time finding info on these two questions. My guess would be that the LC filter would pass the sinusoidal component of the DC pulsed wave...and the hartley/colpitts/watever oscillator makes pulsed DC. Please inform me if these guesses are correct! =)