PSKMeter Build

Parts bag from Software Science Inc
Parts bag from Software Science Inc
The main PCB
The main PCB
About mid way through in about 15 minutes
About mid way through in about 15 minutes
The last of the components soldered in place
The last of the components soldered in place
Ready for testing voltages
Ready for testing voltages
Parts from Mouser for my splitter cable
Parts from Mouser for my splitter cable
Splitter cable soldered, just need to put the hoods on
Splitter cable soldered, just need to put the hoods on
On ttyS0, firmware identified
On ttyS0, firmware identified

One of the aspects of Amateur Radio that holds my interest is the interfacing of computer and networking technology with high frequency radio transmissions. I have been a long time computer geek, it's my primary hobby and my livelihood. After getting my license, I quickly became involved with using a computer to transmit digital signals to other receiving parties, mostly in the form of PSK31, a rapidly growing protocol among Ham radio operators. So, I built my own interface, mostly consisting of simple discrete components like resistors to divide the voltage coming from the computer sound card. I have tuned and adjusted this specifically to what my Icom 706 is expecting on the accessory port (around 100 mVolts max). Not thinking twice, I decided to try the interface out on our club rig which was only expecting around 10 mVolts. Needless to say, my signal was severely over modulated causing my transmission to take up 5 to 6 times the bandwidth it should. This is very annoying for other operators and kind of makes you look like a total n00b. After that fiasco, I tore down my digital interface and expanded the capabilities with a selectable jumper. WHile this looked all good and well on the multi-meter and the oscilloscope. I really wanted to see what my IMD (Inter-Modulation Distortion) values were, but it's not terribly practical to drag a large oscilloscope everywhere I might take my laptop and rig. I came across the PSKMeter from KF6VSG which turns your PC into a mini oscilloscope for PSK, showing IMD values among other points of interest (ok, that's not completely accurate description of what it does, but close enough for this purpose). The kit shipped amazingly fast. I built my own rs-232 splitter cable and supplied my own 12v power supply. The rest of the components where easy to assemble with basic soldering skills, and their construction guide was incredibly well documents. I tested it out last night, using the displayed values into a dummy load to tune my signal to a reasonable value. I got an excellent signal report back from a station in Kansas on 40m at 50w, so I'll call it a success! In summary, it's a nice "field ready" addition to PSK32 operations. It's very well priced, easy to assemble, and cross-platform with software for Windows and Linux (source code also available).