Hiya folks. I've been interested in trying to build myself a radio receiver for various bands, primarily as a learning experience. The thing is, though, I've heard that it's kind of hard to build a stable VFO above 50mhz. One of the bands I'd eventually like to receive is 2 meters (144-148mhz). Might be fun to receive television audio, as well. Not to mention, standard FM.
Since I'm more familiar with digital electronic components rather than analog, I've seen that there are programmable frequency oscillator ICs, which can be set via a microcontroller. This sounds like an easy solution for tuning, and would open the door to setting station presets and the like as well. The problem is, I'm fairly sure that these would output a square wave.
I've read about how you can basically use a low-pass filter to tune out harmonics of a square wave and get a sine wave output. But from the way I understand it, an RC filter would just filter out a specific frequency, defeating the purpose of the variable oscillator.
So that's pretty much my question: How does one turn a variable square wave into a sine wave?
Or, alternatively, what are more reliable ways to produce higher frequency sine waves to begin with? Though I'm still interested in the former question as well, for curiosity's sake.