KI4JJB Sound Card Interface
This is NOT intended as a 'How To'.
I decided to build my own sound card interface. I enjoy these type projects. There are no detailed instructions to be found here, just ideas I hope you can use to build your own project.
Parts I Used
| 1 | 4N35 Optoisolator | ||
| 1 | IC Socket | ||
| 2 | POT 10K Ohm | ||
| 2 | Transformer 600:600 | ||
| 7 | Terminal Block | ||
| 1 | Diode 100v 4.0ns | ||
| 3 | Resistors | ||
| 1 | PC Board | ||
| 1 | LED Red | ||
| 1 | 13 Pin Din Plug | ||
| 1 | Audio Cable |
Total cost was about $15 - $20. Most of my parts came from DigiKey, but a few came from Radio Shack. About half of the cost was the audio transformers. They were about $4 a piece.
Construction
This interface completely isolates the computer from the radio using 2 telecom transformers and a optoisolator. This helps prevent interference between the two.
I decided to allow for level adjustment on both the input and output lines.
A LED indicates when the board is in transmit mode. It is connected via a terminal block. This allows me to swap to a panel mount LED when mounted in a project box without major modification.
My wire to board connectors were selected to allow for multiple connects and disconnects during testing.
I originally planned to connect the ground of each audio circuit to the sweeper of the POT, however, I reversed this because of noise it introduced to the circuit. This may just be an issue specific to my hardware configuration.
There is a diode in the PTT circuit to protect the optoisolator.
I used a label maker with clear labels to finish out my board.
Now there is just one more thing for me to do...
Make my first contact.
73, KI4JJB
