brainwagon

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 […]

Over on NT7S’s Ripples in the Ether blog, he presents a link to a project by Joachim, DL1GSJ, a very nifty little SDR designed to operate near the 30m QRSS watering hole frequncy. It uses pair of subharmonic mixers, whose operation I admit I don’t completely understand, but I’m bookmarking the circuit for later consumption. […]

Well, I’m not sure that the Softrock I put together is working entirely well. I’m beginning to believe that the transformer that I wound might be bad. My receiver seems a bit deaf, and also seems to have only about 20db or so of opposite side rejection (I’m getting images of signals on both sides […]

My dummy load experiment still has a few unanswered questions, but I found that the ARRL Handbook has had a circuit which is basically what I built, minus the one series resistor. It looks like this: Okay, they use a germanium diode with considerably lower voltage drop, and include a 4.7M ohm resistor in series […]