This is a `quick-and-dirty` page that I set up to describe the T1-rate modem that I designed several years ago (in 1993, actually. ) Let me point out that unless you are going to use this on wires, this modem is absolutely useless to anyone other than licensed amateur radio operators: It does NOT intrinsically lend itself to FCC part 15 operation.
Click here to download the full size of the above Circuit.
You are free to experiment with this design as much as you want. All I ask is that you do so legally and, if you make any improvements and refinements, you let me know what you have done so that I can share them with others as well. It is not plug-and-play. What you get are schematics and a description. If you are intimidated when it comes to building things from scratch, then maybe you need to pick another project (or find a friend to help you build it. ) This modem is not the ultimate in optimized design. This is a somewhat refined prototype that DOES work as advertised, as long as it is adjusted correctly by someone who understands what they are doing. This modem uses easily obtainable, off-the-shelf parts that should be available, through only modest effort, anywhere in the world. I am absolutely confident that this design can be improved upon. This is a baseband modem. That is, given a medium that has a bandwidth of 1. 5 MHz (starting at a few 10`s of hertz) and is reasonably well-behaved in terms of amplitude and phase, this modem will push data across it. This is a full-duplex modem (well actually, if you only ever wanted to send data in one direction, that would be fine, too. ) Clock acquisition takes a significant fraction of a second, so you will want to have a path that is there all of the time. Suppose you have wideband FM transmit/receive radio set (Amateur Television FM transmitter and receiver are almost...
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This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
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