I recently ordered parts from various sources, but haven't received them yet. I was itching to build something, and I came across this little square wave test signal generator.
Just a little multivibrator to make a signal. Since it is a square wave, you are going to get lots of harmonics. The idea is that if you just need to put in *a* signal to see what comes out the other side (be it AF, IF, etc), this would be a quick little tool.
I didn't have a lot of free time today, so I decided just to get it working. I needed to use a lower resistor value for RL1/RL2 as he mentioned - I guess the transistors I used didn't have as high of gain as his. I used part of a paper clip for the probe, which worked pretty well.
I'm not sure when or if I'll actually use use this, but it got me my making fix for the day. :)