This 40m transceiver only has around 16 parts, and only a single active device: the ubiquitous IRF510 power transistor which you can even get at Radio Shack. Okay, it’s not exactly a complete receiver: they wired it to a PC sound card, and run an SDR application to get receive audio, but still, impressive!
Daily Archives: 1/28/2010
M1KTA’s QRP ham radio blog: PTO VFO
If you go back through lots of amateur radio designs, you’ll find many, many circuits that use the nearly uniquitous 365pf air spaced variale capacitors that were nearly ubiquitous up until about 25 years ago. In the last couple of decades however, they have become like Avatar’s unobtanium, seemingly impossible (or at least expensive) to find. One solution to this problem is to use varactors controlled using variable resistors (which are still relatively easy to find) but another interesting technique is to build your own variable inductors. Hence, was born the PTO (permeability tuned oscillator), a nifty little homebrew circuit and gizmo that can provide a variable frequency oscillator. M1KTA talks about building one of his own:
M1KTA’s QRP ham radio blog: PTO VFO.
I’ve had this in the back of my head as an interesting project, so seeing notes on someone building one is inspiring.