RS-232 to 100 MHz RF adapter

  
This section describes an experimental low power, low bandwidth data signaling system that operates at 100 MHz (In the FM broadcast band in the U.S.). Before operating a radio transmitter, find out what kind of transmitter operation, if any, is permitted in your locality. Radio transmitter operation is a serious legal matter. In the United States, operation of unlicensed intentional radiators is covered by Part 15 of Title 47 of the Code of Federal Regulations. This design can be readily adapted to different frequencies and different power levels. If you choose to build and operate the transmitter described here, you do so at your own risk. I'm only publishing this as an example of what can be done, and to show how easy it is to build a simple but functional receiver.
RS-232 to 100 MHz RF adapter - schematic

This is an adapter that allows a terminal to communicate via a 100 MHz data channel with peripherals on the same desk top. Keystrokes from the terminal are are received through the RS-232 connection and sent through the 100 MHz RF data channel. See the page, Digital Wireless for the Desktop, on this site, for the basics of the transmitter, receiver, and data format. The reason I made this was to make a simple method of switching between instruments on my desktop. I was staring to accumulate a number of microcontroller-based devices that I want to be able to switch my computer among quickly and this provided the simplest desktop networking solution I could think of. Any data received over the 100 MHz RF data channel addressed to the terminal is decoded and sent to the terminal. The transmit and receive address of the terminal is set by the user and stored in EEPROM. The address field has a range of 0..7, and the transmit and receive address can be changed by entering an escape sequence. The sequence{,T,3}, for example, sets the transmit address to 3. This flexibility allows the terminal to "connect" on any of multiple devices on the desktop by merely entering the appropriate escape sequence. It is planned that most devices will be test instruments and will speak only when spoken to (that is, in response to a request), and that they will all send data to the terminal. This simplifies things a lot because only the...



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