For a few years now, I've been using TR Log software as my contest logging program. Written by Larry Tyree, N6TR, in Pascal programming language, the program operates in DOS. TR Log contains a contest simulator function which can be used as a training tool to improve one's typing, keyboard protocol and contest exchange familiarity, callsign recognition (it uses the a master data file of callsigns, most user-entered from previous contest logs), and code speed. The software's audio output uses the computer's internal speaker.
The PC's speaker, hidden away in its innards, doesn't lend itself to reliable or comfortable CW copying, even in the quietest of environments. My PC resides under my desk close to the monitor (under-the-desktop-type). While running the simulator, I have frequently found myself actually leaning over to the left and tilting my head to try to hear the PC speaker better. Something had to be done. After a bit of digging in my junk box and parts bins and with a little experimentation, I came up with the device described below.
As you can see from the schematic, the circuit is very simple. The hardware mounts easily on a 3.5" or 5-1/4"/harddrive plastic front panel blank. Use the appropriate headphone jack to meet your needs. The pot I used from my parts bin is 7/8" diameter. With some modification to the 3.5" blank, it just fit. The top and bottom 'rails' of the blank had to be notched to allow the pot to fit properly. A smaller-sized pot will work just as well and without the notching. I simply used what I had in my junk box. The PC's speaker leads (red and black) were cut and attached to the new circuit with wire-nuts (X's on the schematic) to facilitate any future changes.
The audio output levels from different PC's may vary. The resistor values I used work fine with my PC. At maximum volume, the audio is not overpowering in my stereo headphones. At minimum volume, the audio is low, but not inaudible. Without the 2.2k ohm resistor, the maximum volume level in the headphones could be extremely loud-I could hear the audio from the headphones laying on the desk when I first plugged them in to the computer. Other PC's may require different resistor values to provide a reasonable range of volume levels. The purpose of the fixed resistor is (1) to limit the maximum volume, and (2) to prevent shorting the audio to ground when the pot is at minimum resistance.
This two- or three-dollar, one-hour project has turned out to be a real benefit. The TR Log contest simulator is now much more fun and enjoyable to use. As a result of now being able to copy the simulator CW more clearly and comfortably, I am using it more, my error rate copying the simulator-generated callsigns has dropped dramatically and my code speed has risen about 25 percent.
