06 02 2010
I came acros the site of IK0VVE with a wonderfull description of a MEPT. MEPT stands for Manned Experimental Propagation Transmitter and is usually very low power. He uses a crystal oscilator but I find them pretty expensive. So I Looked around the net for programmable oscillators. Those are even more expensive and in the most cases you need a microcontroller to programm them. The oscillators uses I²C for setting the frequency by setting the divider and table lookups, ..... I found on oscillator that can be set by a simple resistor : the LTC1799 by Linear Technology Overlooked one thing : it is a Surface Mounted Device (SMD) and I never soldered SMD's before. Oh well. I ordered twee free samples. Two weeks later my wife gave me a big A4 style letter. Just for two devices measuring 3,5 by 1,5 mm 🙂 I managed to solder wires to it. Without a magnifying glass. I'm so proud 🙂 At the moment it oscillates around 10.138 MHz. But it jumps around when my hand comes nearby, strange. It is just ttl level at the output. Will add the 74hc240 first before furter testing. My plan is to use my old Basic Stamp 2 as a keyer for the beacon. Stay tuned for the next article on this subject.