![]() ![]() The first megabit PSK transceivers, , were intended for packet-radio node interconnects. The popular TNC2 will not go much beyond 76800bps, while more recent TNCs lack software support. For medium-speed operation at 38400 or 76800bps, even the simple KISS software is unreliable. Although there is lots of software available for the popular TNC2 or its clones, most of the software is of very poor quality. The development of new TNCs and related software almost stopped. These cards are plugged directly into the ISA bus of IBM PC clones to avoid the delays and other problems caused by external interfaces. ![]() For higher speeds, different interface cards were developed. Today most computers allow a direct steering of a radio modem up to about 10kbit/s, making the TNC completely unnecessary. Unfortunately, the KISS protocol adds additional delays in any packet-radio connection. Most functions of the TNC were therefore transferred to the host computer using the simple KISS protocol, originally developed for TCPIP operation only. In fact, some early TNC software, designed to work with dumb ASCII terminals, represented a bottleneck for efficient computer file transfer or multi-connect operation. ![]() As more powerful computers became available, some functions of the TNC were no longer required. Lots of software was written for the TNC2 too, ranging from simple terminal interfaces to complex computer interfaces and even network nodes. The most popular is the TNC2, originally developed by TAPR (Tucson Area Packet Radio) and afterward cloned elsewhere. Today there are many different interfaces called TNC. The TNC interface lead to a standardization of the protocol used and to a worldwide acceptance of the AX.25 standard. The ASCII terminal required an interface called TNC (Terminal Node Controller). Since at that time computers were not easily available and were much less capable than today, most amateurs started their activity on packet-radio with an old ASCII terminal. Computer interfaces for packet-radio Computers were essential parts of packet-radio equipment right from its beginning more than two decades ago. A simple TNC for megabit packet-radio links Matjaž Vidmar, S53MV 1. ![]()
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