brainwagon

Yep, it’s Christmas again, and I’m such a geek, I can imagine all sorts of things that link it back to radio stuff. If you follow the link below, you’ll find that one of the first (if not the first) audio broadcasts was made on Christmas Eve, 1906, by Canadian scientist Reginald Fessenden. These first […]

I love old books, even  on technical subjects like radio.  Often, by looking at the books of the past, we find them more accessible (because there was less knowledge, they assume less as a precursor) and also possess considerable historical interest. Letters of a Radio-Engineer to His Son is a nice little book by John […]

G3XBM pointed out silent key KL7R’s modification of a Heathkit HW-8 to do double sideband voice. It looks pretty straightforward, and would be an interesting modification. My own HW-8 isn’t exactly pristine, but I am torn between keeping it in its native state, and performing a modification to make it more versatile. Bookmarked for later. […]

Eldon, WA0UWH pointed out WA4DSY’s website that features an active filter design applet. I was just waking up this morning, so I thought I might give it a try. I used LTSpice’s universal op-amp node, and wired it for positive and negative voltage feeds. I specified a 2.2uH value for the caps, and a 800hz […]

I’ve never attended Dayton or FDIM, but I am thinking that perhaps I will soon (hopefully this year). An affiliated event is the Four Days in May: the QRP event for the QRP Amateur Radio Club International. They are hosting a building contest this year: QRP Amateur Radio Club International – The FDIM 2010 QRP […]

As I might have mentioned, I am trying to teach myself a bit about electronics and radio design. I find the problem with being self taught is that often you read something, and it doesn’t seem clear to you why it should be so, and you uncover the basic lack of understanding that you have […]

OZ9AEC shows how you can use free software and web-based radio receivers to decode amateur digital communications. Very nifty. I tried this myself using WebSDR, and it worked great. httpv://www.youtube.com/watch?v=GB9Ed02Vhr8

So, for fun, I entered the circuit for the bidirectional amplifier used in the BitX20, and did some basic simulation. You can see it in the image linked below. I was trying to figure out how to instrument the schematic so I could determine the input and output impedance (and eventually things like return loss […]

A couple of projects that I’ve been pondering could make use of a little temperature sensing chip. Microchip makes this little gadget, the MCP9700A, which could be quite useful, and can be had for about $.35 from Digikey or Mouser. It comes in a simple TO-92 package, or smaller surface mount chips. MCP9700A-E/TO-ND.

Bruce, VE9QRP has a nice video demoing his qrpTracker code (open source) running on an Atmel AVR microcontroller and tracking the Doppler of a cubesat as well as AO-51. Nifty. httpv://www.youtube.com/watch?v=XgNcCGXeRyw Addendum: Back in January of 2008, I acquired my (then) new FT-817, and one of the first projects I did was to use my […]

Got some interesting spots overnight. VK6BMW is located in Perth, Australia, which is pretty close to the maximum distance I’ve heard before. PA0LSK is in the Netherlands (any European spots are pretty rare for me). CO7WT is my first Cuban station spotted I think. Not a bad night. Timestamp Call MHz SNR Drift Grid Pwr […]

Well, one of the advantages of getting a new Windows 7 laptop is that I now have a much nicer environment for running LTSpice. Does anyone have any ideas of a good, simple project that I could do to help me learn the ropes of LTSpice, and which I could also build for real to […]

Left my FT-817 beaconing for the last 48 hours or so, mostly on 40m, and got some interesting DX, including someone I think I never reached before, KG6DX in Guam. Timestamp Call MHz SNR Drift Grid Pwr Reporter RGrid km az  2009-11-27 07:32   VK3AMW   7.040092   -19   0   QF22ir   5   K6HX   CM87ux   12668   59   2009-11-27 07:08  […]

Well, I finally dug up all the cables I needed and hooked up my little HP netbook to my radio again, and got it going with the new WSPR 2.0 software. As of this moment, I’m beaconing out at 5w on the traditional 30m watering hole, and getting pretty good domestic spots. I might try […]

John, K8YSE recorded a North American pass of SO-67 (the new South African ham satellite) and posted the audio on his website. It appears the audio quality is actually pretty good. I’ll have to be trying it out fairly soon. SO-67_22Nov2009_141052z.mp3