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AE5ME > ARES 27.03.16 05:48l 12 Lines 2576 Bytes #999 (0) @ WW
BID : XB3W3XEB60E0
Read: GUEST
Subj: Digital Emergency Communcations Series by AD5XJ (SATE
Path: IW8PGT<IZ3LSV<I0OJJ<GB7CIP<N0KFQ<AE5ME
Sent: 160327/0317Z 34291@AE5ME.#NEOK.OK.USA.NOAM BPQ1.4.64
DIGITAL COMMUNICATIONS (part 1) by AD5XJ ad5xj@arrl.net
Disclaimer: These are my comments on digital communications and are not necessarily all there is to know on the subject. As with everything computer related ? there are at least six ways to do the same thing. Given this caveat, let me say this is opinion and not the complete story. I only relate to you my experience of 5 or more years using digital modes, and acting as the SATERN So. Terr. Digital Net Manager for almost as long, to give you the benefit of my experience. I will leave the rest for you to research the references we will provide at the end of this series.
In this series of articles we will take a cursory look at some terms used in ham radio while talking about common digital modes. We will also take a look at some of the software available for digital radio as well as the pros and cons of each. What we present is not all the software available nor does it attempt to be comprehensive. There is no substitute for experience with digital radio and the associated software and hardware.
If you have been interested in what digital communication is all about, this series may give you a deeper understanding of the terms and uses of common digital software in ham radio.
BASIC TERMS
DIGITAL COMMUNICATION refers to the translation of text or other data (images, PDFs, etc.) into digital information to be transmitted by conventional modulation methods allowed by amateur radio operators. Amateurs have about seven frequently used modulation methods including AM, FM, SSB, FSK, and CW to name only a few.
Some digital methods use CW. Yes CW Morse code is a digital mode! Similar to CW is FELD-HELL. This strange mode uses a rapid on-off CW like modulation to create digital information that is displayed for human readability. FELD-HELL is very spectrum efficient in that there is a single frequency used with very narrow spectrum use. Usually only 50-90 Hz wide. It is not a commonly used digital mode for emergency messages because there is no error correction and is very slow compared to other more widely used modes.
Some modes use Frequency Shift Keying (FSK). Addtionally, some modes like RTTY can use more than one method - FSK or AFSK. AFSK is a method where audio frequencies of AM or SSB are shifted instead of RF carrier frequencies.
Regardless of mode, digital pulses are used to send information (data or text) by conventional modulation methods.
The conversion of digital data to transmitted data is performed either by hardware or software (and in less conventional cases, both).
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