Laptop & Radio
Digital modes for datacommunications
The combination of laptop and radio is now common in the outdoor area. On the one hand, the user has the option of using the laptop as an “office” where all important data can be edited and saved, and on the other hand there are programs that offer special communication options in connection with a radio device.
Depending on the intended use, different "digimodes" are available for data transmission.
The signals to be sent are output by the sound card and then sent with the radio. A Terminal Node Controller (TNC) such as a modem can also be used instead of the sound card.
An overview of the currently most common digital operating modes can be found on the website of the "German Amateur Radio Club e.V." (DARC) under the heading "Digimodes".
A galvanic separation of PC and radio is important to avoid mutual interference between PC and radio. This means that the two devices are not electrically connected to each other, but the data is forwarded. Audio signals are separated with a so-called transformer, which is a small transformer. Optical couplers (optocouplers) are used for data lines that transmit a digital signal. The "information" is transmitted in a contactless manner by means of light pulses. In addition, toroidal cores and snap ferrites are used to reduce interference.
Connection cables of the devices: This area usually has the biggest problems, as there is no one-size-fits-all solution. You will not be able to avoid studying the operating instructions for the devices used, because the plugs and their pin assignments can differ not only from manufacturer to manufacturer, but also from device to device. If you want a quick and easy solution, retailers offer "all-in-one" devices that can produce galvanic isolation, an integrated sound card and all connections between PC and radio. Two examples that are used successfully by many radio operators should be mentioned: The “Micro Keyer II” as a station device and the “Signa Link USB” as a mobile device. The cables must then be ordered depending on the radio device. The functionality of such devices goes far beyond what is actually needed. But you have the advantage that they can be used for all digital operating modes and are compatible with almost all amateur radio devices.