Archive for the Projects Category

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, ..... (more…)
 This article is a reprint from my original article published in 2004. I don't use the antenna anymore (collecting dust in the basement) but the article will stay here for informational purposes. I live in an appartment and don't have the space to put up a large antenna for my Kenwood R1000 receiver. I knew the excistance of magnetic loops, but I never spent time to take a look at it. Why ? Who knows. For the main loop I used a soft copper tube, diameter is 10 mm, length about 3 meter. Try to make a circle (not always easy). A friend of me, Carl ON7NH, has drilled and tapped M3 tread into it. This makes it possible to use solder lips. The entire loop is constructed on a sunday afternoon. The smaller loop is about 60 cm in length (diameter 1/5 of the main loop), material is 1,5 square mm copperwire. With the capacitor found in my junkbox, I can tune the loop from 2,9 Mhz till 10 Mhz. Other capacitors will give other tuning ranges, have to experiment here.
This post is taken from my old website. I'm still dismantling that site. What is PMR446 anyway ? PMR446 stands for Personal Mobile Radio and is a license free radio in the 446 MHz UHF band. That is about 6 Mhz above the 70cm amateur radio band. There are 8 channels starting at 446.00625 MHz and ending at 446.09375, spaced 12.5 kHz apart. (more…)
Ham radio operators interested digital modes will often use these computer interfaces to automate CW contacts (send morse code from the PC), use the PC soundcard for RTTY and control push-to-talk functions among other things. Many of the PTT interface drawings  found on the net suffer the same problem. Well it is not really a problem.
Let's have a look at a typical interface :interface_before.jpg You have the RTS and DTR line tied together with diode, then comes a transistor that operates as a switch. And finally the ptt line from you transceiver. So when the RTS or DTR signal goes high, you are on the air. So what is the catch ? Ever booted your computer or used other software besides your regular hamradio soft ? Of course you did 🙂 and what happened ? My transceiver went in to TX on the wrong antenna / receive converter / mistuned antenna. Luckely the radio was set in SSB and no harm done without modulation. But it could be worse. interface_after.jpgSo what have I done ? A simple modification that costs almost nothing : add a simple switch in the PTT line. See the red switch in the interface drawing. That's it. When the computer has booted and ready to use, I toggle the switch and can operate the digital modes.
I'm currently experimenting with a PIC processor. The term microcontroller is actually better, but you know what I mean. It all started when reading about the bitx20 kit. This transceiver has no frequency readout and if you look around you'll notice that everyone is using a PIC or an AVR to build a frequency counter with LCD readout. I knew little about PICs, nothing about AVRs. Not that I dislike AVRs but PIC feels better to me personally. (more…)
From left to right :
  1. The kit has just arrived.
  2. The PCB, nice and clean job.
  3. What I did in january.
  4. Where I stopped in march.
bitx20-kit-jan2008bitx20-pcbBITX20-jan2008BITX20-march2008 More to come.
Like many amateurs I have more than one project that needs attention. Here's a list what is keeping me busy :
  • Cantenna for 23cm
  • Short 40m inverted V dipole
  • BITX20 tranceiver kit
  • 23cm ATV biquad antenna
  • Antenna switch box 1x6
  • Pic programming for the BITX20
  • Make cables for a small LCD panel
  • ...
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