{"id":85,"date":"2018-12-07T15:47:01","date_gmt":"2018-12-07T15:47:01","guid":{"rendered":"http:\/\/burnhamradioclub.co.uk\/?page_id=85"},"modified":"2019-02-09T13:32:07","modified_gmt":"2019-02-09T13:32:07","slug":"transmission-modes","status":"publish","type":"page","link":"https:\/\/burnhamradioclub.co.uk\/index.php\/transmission-modes\/","title":{"rendered":"Transmission modes"},"content":{"rendered":"

Modes of communication<\/span><\/h2>\n

Amateurs use a variety of voice, text, image, and data communications modes over radio. Generally new modes can be tested in the amateur radio service, although national regulations may require disclosure of a new mode to permit radio licensing authorities to monitor the transmissions.\u00a0Encryption<\/a>, for example, is not generally permitted in the Amateur Radio service except for the special purpose of satellite vehicle control uplinks. The following is a partial list of the modes of communication used, where the mode includes both\u00a0modulation<\/a>\u00a0types and operating protocols.<\/p>\n

Morse code<\/span><\/h3>\n

Morse code<\/a>\u00a0is the original digital data mode. Radio telegraphy which is the direct on\/off keying of a continuous wave carrier by Morse code symbols, often called\u00a0amplitude-shift keying or ASK<\/a>, may be considered to be an\u00a0amplitude modulated<\/a><\/i>\u00a0mode of communications. Although more than 140 years old, bandwidth efficient Morse code, originally developed by Samuel Morse and Alfred Vail in the 1840s, uses techniques that were not more fully understood until much later under the modern rubrics of\u00a0source coding<\/a><\/i>\u00a0or\u00a0data compression<\/a><\/i>. The bandwidth efficiency of Morse code arises because the most used source symbols were accorded the shortest Morse code symbols and the least used were accorded the longest symbols by Vail and Morse. Vail and Morse intuitively understood bandwidth efficiency in code design. It was not until one hundred years later that\u00a0Claude Shannon’s<\/a>\u00a0modern\u00a0information theory<\/a>\u00a0(1948) put Morse and Vail’s Morse code technology on a firm theoretical mathematical footing, that then resulted in similar Morse code-like bandwidth efficient data encoding technologies such as the modern\u00a0Huffman<\/a>,\u00a0Arithmetic<\/a>\u00a0and\u00a0Lempel-Ziv<\/a>\u00a0codes. Morse code is still used by\u00a0amateur radio operators<\/a>. Operators may either key the code manually using a\u00a0telegraph key<\/a>\u00a0and decode by ear, or they may use computers to send and receive the code.<\/p>\n