brainwagon

Today, I felt some compulsion to work on something radio related. A couple of weeks ago I build the crystal oscillator from Chapter 1 of Experimental Methods in Radio Frequency Design. I was lacking the necessary toroid to continue building the buffer amplifier, so I had ordered some from Doug Hendricks at qrpkits.com. They arrived […]

VK6DI reported that he was picking up W1BW’s 100mw beacon signal (a distance of over 11,000 miles) today, so propagation was obviously pretty good. Here’s the screengrab that he sent to the Knights mailing list: Bruce also sends out a simultaneous WSPR message, and David recorded a simultaneous capture of his WSPR beacon. Right around […]

Just for fun, I decided to try to see how many states had reported hearing my WSPR beacon. Turns out the answer is 32. All the bold, green colored states below have at least one reception report. All the thin, red colored states need some ham to spend some time running WSPR and reporting his […]

Yesterday, I recorded a couple of hours of signals off of 30m, and ran them through my homegrown spectrogram code for fun. I found the following FSK CW signal (click on it to get it larger): (The blank regions are the two minute intervals where I am sending a WSPR beacon message.) With a bit […]

I got home fairly late last night, and wasn’t up to any serious radio activities, but I did activate my WSPR beacon on 40m, and let it run. This morning, around 8:00AM local time, I was treated to a pretty good haul of DX spots especially from VK4 land. I had spots from VK4ZW, VK4YEH, […]

This morning as I was heading out the door, I scanned my bookshelves for something that I could read during my lunchbreak. Much to my astonishment, I saw this book: Yes, that’s right: a copy of Wes Hayward and Doug Demaw’s classic Solid State Design for the Radio Amateur. I’d been looking for this thing […]

Steve has an interesting post entitled “Golden Rule and Imagined Worlds” on his blog. It’s an interesting post, suggesting that transparency and equality are the basis for a good club. I’m not sure I disagree, but I am going to take a different tactic, and it will be of the following form: how much “organization’ […]

Bill is building an FETer (Transceiver Made with One FET) as published in Sprat by G3XBM. I don’t get Sprat (but should), but you can get the design off this web page. A very simple, truly minimal design. It’s like a haiku constructed from solder. I have some MPF102s in my junkbox. I might just […]

Got a quick recording of the PRISM satellite, launched on the 23rd, as it came over my location. It was booming in, very fast Doppler. Here’s a recording and a quick spectrum of it, click on the image to get the spectrum of the 2 minute mp3 recording. MP3 of the Japanese PRISM satellite on […]

Goofing around while watching Battlestar Galactica (which incidently is one of the most depressing, soul-less, unfun thing to watch that I can imagine) and decided to look up George Dobbs’ QRP harmonic lowpass filter design, and see if I could get it to analyze using ngspice. I picked his design for 30m, and created the […]

Here’s a nifty PDF on QRP transmitter design. It looks like it might have been cribbed from one of Doug Demaw’s books (which you should buy if you are interested in this stuff), but it’s just a few pages long, and is quite practical. I think I’m actually getting to the point where I understand […]

Okay, I’ve been reading some of my variou sources on amplifier design including EMFRD and the ARRL Handbook, and decided to try to test my understanding of them by coding up a simple common emitter amplifier, and then testing the model by plotting out the voltages using ngspice, the open source version of the popular […]

Need to make a quick and dirty schematic drawing? Try the Klunky Schematic Drawing page.

I was digging around information on common emitter amplifier design, and encountered this link which seemed quite helpful. Digging around the All About Circuits webpage, which seems to be a very useful online reference. It helped me understand the presentation that I’ve been reading in my copy of Hands-On Radio Experiments. More on that soon. […]

Well, you can’t do better than an article by the legendary George Dobbs, G3RJV. The circuit that he has closely resembles the oscillator that I just built, with a few distinctions. A Universal VXO by George Dobbs G3RJV The general topology is the same, but the resistive voltage divider that feeds the base of the […]