Since I brought up the problem of distortion and gain control a few posts ago, I felt responsible for addressing it. Attached is a schematic for the Colpitts oscillator that I previously posted, but with a diode limiter added. If a diode limiter is inserted in the proper place in the feedback loop, it will accomplish nearly the same thing as a fancy AGC circuit, but with far fewer parts (unless you happen to have the perfect light bulb at hand). The output pic shows a fairly clean sine wave. Output amplitude is dependent on the ratio of the feedback resistors R1/R2.