The Cranky Sysadmin A world of technology, fun, and ignorant rants.

August 10, 2013

More DSP Resources (and maybe a little math)

Filed under: Electronics,ham radio — Cranky Sysadmin @ 2:51 pm
  • A Visual Intuitive Guide to Imaginary Numbers. Imaginary numbers used to make my head hurt. If you’re shooting for your General or Extra class ham license, they will make your life easier. They’re also the basis for a lot of DSP work.
  • Quadrature Signals. Also explains complex numbers and then does a deep dive into quadrature signals which are used in a lot of aspects of DSP.
  • Bores Introduction to DSP. Somewhat math heavy with summations and integrals, but still an approachable introduction.
  • dsPIC tutorial and “Robotics 3.1“. Dig around on these blogs for basic information about how to use the dsPIC30 series PIC DSP processors. Most of the examples don’t seem to need the DSP portion of the chip, but it will get you started without going to basic PIC microcontrollers.
  • AE6TY. This ham does a great job of explaining his SDR implementation using DSPIC and some ADC’s. Don’t miss his Intro2SDR under the papers section. His DSPExplorer application looks nice too but I’ve only taken a cursory glance at it so far.

July 13, 2013

DSP Resources

Filed under: Electronics,ham radio — Cranky Sysadmin @ 9:59 am

I’m learning DSP basically from the ground up without an advanced math background. My goal is to gain a deep understanding of digital signal processing (I’ll define deep when I’m tired of learning). Below are some of the resources that I’m using to get started. As I find more resources, I’ll add them here.

  1. Analog Devices DSP Primer. A very brief 10,000 foot overview.
  2. FFT for dummies. This page doesn’t actually get into the details of Fast Fourier Transform, but it does describe sampling methods and how to interpret the output of FFT programs.
  3. The DSP chapter in a recent ARRL Handbook. Chapter 15 in the 2013 edition. This has an overview and PIC based examples of the pieces of a software defined radio.
  4. Signal Processing for Communications. I have only started reading this free online resource. It is the textbook for the Coursera DSP course. It’s available for free Download.
  5. The Scientists’ and Engineers’ guide to Digital Signal Processing. I haven’t started reading this yet. It’s available for free download or hardcover purchase.
  6. Calculus Made Easy. I have a newer edition with more chapters. If I want a deep understanding of DSP, I am probably going to need to learn Calculus.
  7. Experimental Methods in RF Design chapters 10 and 11 (revised 1st edition). Looks like lots of practical stuff here. They use an ez-kit lite adsp-2181 which I’m having a hard time finding.

June 30, 2013

Don’t Disturb the Dust!

Filed under: Electronics,ham radio — Cranky Sysadmin @ 11:39 am

My Heathkit® project took a turn for the worse yesterday. There was some occasional arcing in the audio section when I turned on the radio. The cause seemed to be the sediment on the board. Do you know that feeling you get when you’re about to do something bad? Yeah, I’ve discussed this before, and I ignored that feeling again. Instead of taking the safe and lazy route of tracing down where the arcing was coming from, I decided now was a good time to lift the audio board out and clean it up. As the dear reader might predict, the audio section is now non-functional. I’m pretty sure things are wired up correctly. My current suspicion after triple-checking the wiring is that I disturbed some marginal component enough to stop it from working. I’ll have to look at after I complete some other easy projects that have been languishing, like my solar charging station and short vertical antenna.

June 25, 2013

The Tubes All Light Up. It Must Be A-OK

Filed under: Electronics,ham radio — Cranky Sysadmin @ 7:27 pm

After the great HW-100 conflagration of 2013, I figured I’d proceed with more caution in powering up the radio. I rewired the power cable, then looked over the HW-100. I replaced the electrolytic caps, and I found the source of the loud pop during my initial test. Fortunately, it was just what looked like solder dust on the audio board. I cleaned the boards up as good as I could without tearing it down. I then proceeded to power up with care. All of the tubes light up, and there is no smell of burning electronics. I plugged in a pair of head phones and tuned around. The radio appears to receive on all bands though it seems a little deaf on 20 meters. I am so glad I didn’t burn up anything obvious. Tomorrow, I will start the alignment process.

June 24, 2013

Hard Lessons About Old Heathkit® Gear

Filed under: Electronics,ham radio — Cranky Sysadmin @ 8:26 pm

I recently purchased an old (possibly older than me) Heathkit® HW-100 transceiver and a HP-23 (the “first edition”). After getting it home, I immediately proceeded to plug it in and test it. You know that nagging feeling you get when you’re doing something you shouldn’t? Well, I ignored that. When I plugged in the supply, the fuse popped. I took a look inside. It was wired wrong in several ways. While I spent time rewiring it, I noticed that the electrolytic caps were light as a feather. I replaced those and tested the power supply with much better success. Don’t trust the ebay add that states “tested good”.

I then proceeded to plug in the 11 pin cable to the power supply and the HW-100. You know that nagging feeling you get when you’re doing something you shouldn’t? Well, I ignored it again. I powered up the radio. There was a loud pop in the radio and one of the audio tubes glowed white hot. By now you see the pattern of my misdeeds. It turns out that the cable is wired completely incorrectly for an HW-100. It almost looks like it’s mostly wired partially backward.

Well, once I fix the cable, I’m going to give the HW-100 a good going over. The ebay sale listed a litany of problems which looked fixable. Now it has at least one more problem. I hope I have the tubes and components to fix my mistake.

June 12, 2013

Arduino Capacitive Touch Iambic Key (using attiny85)

Filed under: Arduino,Electronics,ham radio — Cranky Sysadmin @ 9:19 pm

Since I’m trying to learn morse code, I decided I’d build a key which functions as a trainer and an actual key. I’ve always liked the idea of capacitive touch sensors, so I went with that. This is a small project using a handful of parts. One should be able to finish it in an evening of focused work. Read on if you’re interested in the details.
Iambic key details

June 9, 2013

A Field Day Antenna for 80 Meters part 2

Filed under: ham radio — Cranky Sysadmin @ 2:32 pm

I’ve made some progress on my short vertical for 80 meters. I put it up in the air and added the guy wires. Some pictures and commentary are after the fold.
The Fold

May 27, 2013

A Field Day Antenna for 80 meters (I hope) pt.1

Filed under: ham radio — Cranky Sysadmin @ 7:20 pm

I spent this weekend starting work on an 80 meter antenna. The design is pretty pedestrian, but I’m hoping for acceptable performance. If I’m lucky, I’ll be able to get the antenna onto 160 meters with reduced performance.
A boring short vertical

May 11, 2013

Abandoning Antenna Analyzers. Moving on to Antennas.

Filed under: ham radio — Cranky Sysadmin @ 7:01 pm

After learning a lot about antenna analyzers over the past few months, but not actually building a portable functional model, I settled on a very simple antenna analyzer based on the 74HC4046 pll chip. There are several designs that use this chip. I decided to combine the dual range vco from PE2ER’s design and the simple output from the tenna dipper. I thought this was novel, but of course someone has already done it and called it the deluxe tenna dipper. The schematic is so close to mine that I don’t care to post mine here. After all this work though, I found an MFJ-259b for sale at near-fest. It was a great deal, so I took a chance.
Onward to Antennas

May 1, 2013

But Morse Code is Dead

Filed under: ham radio — Cranky Sysadmin @ 9:47 pm

I’ve been building QRP radios for other folks who use Morse Code. It seems that in the process, I’ve contracted the desire to learn Morse Code myself. As time permits, I’m attempting to use LCWO. I like the site a lot. The application includes sufficient statistics, a clean simple interface, and a lot of options to change if you so desire. The site doesn’t include ads, which is nice, but ads wouldn’t dissuade me from using the site.

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