I don't recall ever seeing an RC oscillator driven RF transmitter or receiver.
What prevents people from choosing RC oscillators in RF design?
I don't recall ever seeing an RC oscillator driven RF transmitter or receiver.
What prevents people from choosing RC oscillators in RF design?
I'm going to discuss filters and not oscillators, because the reasons are pretty much the same. An oscillator is just a filter with enough gain to put it on the edge of stability.
It certainly is possible to use RC filters in RF design, and sometimes you do see them in non-critical filters, especially those that don't require a steep filter or high power handling, such as AC coupling between stages. Reasons you might not want to use inductors:
Resistors and capacitors also have non-ideal properties (lead inductance) and aren't free, but the magnitude of these problems is less.
Reasons you might want to include inductors in your circuits:
The transient response of an RC circuit driven to oscillation by negative feedback generates a much higher proportion of harmonics than a similar LC circuits response. These harmonics have to be either filtered out with additional circuitry, or the oscillation needs a significant amount of post-processing (such as using it to clock an SDR or a digital synthesizer), in order to produce a clean enough waveform to meet legal requirements for RF transmission.
PLLs in receivers may or may not need as clean a waveform, depending on the receiver design.
RC oscillators have high levels of sideband noise. I do not know whether one could mitigate that by connecting RC filters in series, but it seems unlikely to me. A good LC oscillator uses the fact that the impedance depends on the frequency. With a parallel crystal resonance, the amplifier would see a low impedance far from the resonance so the wideband noise floor would not be determined by the noise near the resonance where impedance is high. Likewise, an osscillator using a series resonant crystal would have a very low gain off resonance because it would use a grounded base/gate configuration where gain is inversionally proportional to signal source impedance.
Maybe this page can help to understand the problems: http://www.sm5bsz.com/osc/newref.htm