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

April 21, 2013

A Break from Antenna Analyzers (Pixie II Transceiver)

Filed under: Electronics,ham radio — Cranky Sysadmin @ 8:59 pm

I took a break from antenna analyzers to find and build a rig for a friend who is in a nursing home. The requirements are:

  1. It should be very small and portable. A nursing home doesn’t have a lot of space.
  2. It should be a CW rig. My friend is proficient with CW.
  3. It should be easy to build.
  4. I need to find the components in my junk box.

More on the Pixie II

April 12, 2013

Antenna Analyzer Progress Part 2(ish)

Filed under: Electronics,ham radio — Cranky Sysadmin @ 9:42 pm

I’ve been studying detectors for antenna analyzers and trying to land on one which will be effective. If you’re interested in detectors, read past the fold.
The Fold

March 10, 2013

Arduino DDS Signal Generator Details

Filed under: Arduino,Electronics,ham radio — Cranky Sysadmin @ 7:44 pm

Past the fold are details on my rendition of an ardiuno DDS based signal generator. Included are the code, some schematics (not a full schematic though), and some hints on setting it up.
Signal Generator Details

March 9, 2013

First Crack at a Simple Antenna Analyzer

Filed under: Electronics,ham radio — Cranky Sysadmin @ 8:32 pm

I’ve built a prototype of my first antenna analyzer. Pictures and some details below.
First Antenna Analyzer Details

March 7, 2013

Obsessed with Antenna Analyzers

Filed under: ham radio — Cranky Sysadmin @ 10:38 pm

Rig Expert Ukraine has a great summary of many popular antenna analyzers with descriptions of each family. There are lots of different types, but they all have some common components:

  1. Signal Generator
  2. Detector
  3. Calculation and Presentation

I’m considering starting with the simplest architecture and working my way up until I’m satisfied with performance, or I’m bored. I’ll probably pass on 90 degree phase shifts as there are other (perhaps less accurate) ways to derive the sign of impedance. As I build some complete projects, I’ll post results and details.

March 3, 2013

Sync Two AD9850 DDS Modules from the Same Clock

Filed under: Electronics,ham radio — Cranky Sysadmin @ 9:51 am

One of the features which I’m trying to build into my antenna analyzer project is to measure whether the impedance in the antenna is capacitive or inductive. Judging from other designs, this means I will need two signal sources which are 90 degrees out of phase. The AD9850 data sheet mentions this feature, as do several other ham sites, but I haven’t found a really good description about how to get it done.
The Ugly Details

March 2, 2013

A Buffer and Amplifier for a DDS Signal Generator

Filed under: Electronics,ham radio — Cranky Sysadmin @ 11:02 am

A google search for DDS buffer amplifier turns up some nice results in the first two hits. These circuits are very similar. My rendition of this circuit replaces the 2n2222 with 2n3904’s since I have scads of them. I also lower the value of the feedback resistor to 470 ohms (R3 in my schematic). This lowers the output voltage a bit, but it also seems to cut back on the harmonics. With 1k feedback I was seeing the second harmonic at 10db down from the original signal. With 470 ohms, the second order harmonic was down between 34 and 40 db over the whole range of tuning.
Schematic and picture to follow

February 27, 2013

Why Become a Ham?

Filed under: ham radio — Cranky Sysadmin @ 8:21 pm

A friend of mine from Finland discovered the hobby of amateur radio a few days ago. He doesn’t have a license or a rig. As far as I can tell, the hobby just looks interesting to him. That got me thinking about why someone would want to become a ham radio operator.
No, not that kind of ham

February 26, 2013

Arduino Signal Generator Demonstration

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

I have a lot of work to do on my arduino DDS signal generator, but it’s good enough to demo. Too bad I’m bad on camera. Once I have this signal generator to the useful stage, I’ll post some details about it.

February 25, 2013

Antenna Analyzer Progress 1

Filed under: Arduino,Electronics,ham radio — Cranky Sysadmin @ 8:21 pm

I spent a fair portion of the weekend testing my new AD9850 DDS modules and attempting to use some bare AVR chips with internal oscillator as cheap arduino. Read past the fold if you’re interested in the progress.
The Fold

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