Saturday, October 27, 2012

USBlink Digital Interface

One of my favorite modes is PSK31. I had seen the USBlink project on the fine website of Julian, G4ILO, and the project looked downright useful.
Julian used a cheap USB sound card dongle. Mine cost under 5 dollars US including shipping. The rest of the USBlink is the Skip Teller digital interface circuit for PTT to the transceiver. There are several things I like about this interface project. First is the USB cable. I built the original Skip Teller KH6TY interface from the June 2009 issue of QST. I like the function of the interface, but not the two audio cables hanging out. The USB cable is a nice alternative, no fumbling with which cable is mic and which is phones, just plug in the USB. I built the interface with a six pin din connector. The main reason for the six pin din was my FT817 and Icom IC703 have that connector for digital connections. Interestingly enough, both radios have the same pinout. I can make one cable with straight through connections and not worry which end is plugged into the radio or the interface.
I made only two departures from the USBlink original. First was the the USB connection, I wanted the B type USB connector so I could use a standard B to A cable which you can steal off your USB printer in a pinch. I picked up a female B and a female A connector and wired them together. The dongle plugs into the A connector and the external USB cable plugs into the B connector. The second difference was the green LED. Just like Julian did, I clipped off the green LED from the dongle and soldered wires to a larger LED mounted on the case. I noticed however, the green LED was much brighter than the red Transmit LED. I wanted both LEDs to be about the same intensity so I put a 1K resistor in series with it and now they are visually comparable.
This project is nice, compact, and inexpensive. I got the box and components from my junk box. The purchases were the USB connectors, the sound card dongle and the cable and din connectors. The entire project cost $15 tops. I was in need of a nice 4 conductor cable for the project so I went to RE-PC in Seattle and in the used cable area, got a 15 foot USB cable for one dollar. I clipped the ends off and have enough cable to make five, three foot cables. I don't have that many radio's but I'm sure the cable will come in handy for other projects.
Bob, AD7BP