For many radio amateurs, talking & chit-chatting on-the-air is of no interest. They rather like to "Silently" work on their bench with hobby projects & communicate with fellow amateur by way of a PC and a modem connected to wireless set.

There are lots of ideas & radio modems available to fill this requirements. I have gone thru this 15 years back when I first bought a Kentronics all mode TNC and later a 1200baud VHF TNC. 

Here I have presented two such "Modems" which are not really modems but give us the same results at a fraction of cost.

The first is called "Hamcom" a PC software (DOS) written by  . It has a very simple interface to PC com port containing a ua741 and few components. Most work of a "TNC" is done by the software.

You get a simple, economical & fast way to start digital communication on amateur bands with this kit & a free software. With Hamcom you can receive & transmit RTTY & CW.

Similarly, PC's soundcard is nothing more than a modem itself. Using soundcard capabilities for Digital Communication has attracted many hams to use a simple interface to isolate PC & Radio to achieve clean signals & reject noise and spurious frequencies.

Sound card Interface detailed below does this.

The soundcard interface detailed here is not different from many made by amateurs and available commercially.

SC1 is simple to construct and easy to use. On this interface, you have an RJ45 connector where you connect your microphone, PTT and Receive audio using a shielded cable.

SC1 is a passive interface. Means, it dosnt require any external power. 

                  

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