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

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.

It’s not immediately apparent how to setup a bare atmega328 with an internal oscillator and an arduino bootloader. This discussion on arduino.cc was helpful for setting up the arduino software. The settings it suggests mostly differ in the fuse settings to enable the internal oscillator and the serial port speed. There was some discussion in this thread about the possibility that 38400 bps might not be stable. I will only be using it for loading the program in ideal (read room temperature) conditions, so I’ll take the chance. This site has a lot of good info on the hardware side of setting up a bare bones arduino. I couldn’t get his suggestions about how to run at 8mhz to work though.

This evening, I breadboarded an old 5 volt Clarostat rotary encoder and a 3.3 volt GLCD5110 LCD (like the common Nokia displays). These are controlled from the bare bones Arduino. I used a voltage divider (five of them actually) consisting of a 22k ohm resistor and a 10k ohm resister to interface the 5v AVR chip to the display. I chose the Nokia display because it can be addressed like an 84×48 bitmap which gives me more flexibility than the 2×16 text displays that I have available. I may want to display simple swr plots and smith charts.

Next on the agenda is to add a pushbutton to control the speed of the frequency adjustment, and then add the DDS to make a signal generator. I’m still trying to sort out what kind of amplifier I’ll need so I can feed the directional coupler or bridge. Once I get the full signal generator together, I’ll put up some pictures or a video.

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