There are three characteristics you can change on an RF signal: amplitude (CW, AM, SSB, etc), phase, and frequency. Even then if you squint a little phase and frequency modulation become basically the same. So the fundamental methods of modulating a signal are all known and used. Nothing new there. Mixing those in various ways gives all the different digital modes of operation. What has been realized in with the advent of digital signal processing (DSP) is all the modulation and modes are mathematically related using sine and cosine functions that are mixed to provide the final signal. The real unknown is how to maximize throughput to approach the Shannon Limit. An open question is whether deciphering such a message can be done in a reasonable time frame. We currently have digital techniques which are efficient but are only suitable for message passing, not chatting or voice, since the latency is on the order of seconds. - 73 - Rud Merriam K5RUD ARES AEC Montgomery County, TX http://TheHamNetwork.net <http://thehamnetwork.net/>
-----Original Message----- From: Gmail - Kevin, Natalia, Stacey & Rochelle [mailto:spar...@gmail.com] Sent: Sunday, February 22, 2009 5:30 PM To: digitalradio@yahoogroups.com Subject: [digitalradio] Modes - What are they and What about New Developement?? Hi All, I am hoping with the number of members in this group that someone might be able to answer my question. Many years ago, as we know radio started off with CW, then AM was developed, with an improvement to only use one part of the AM carrier to produce SSB with carrier or SSB suppressed carrier. Then somebody developed FM. Now in my view this gives 4 actual modes? But I see you say (Maybe), we have all the digital modes. But are these actually modes? Why I ask and the reason for the question, is these are still using one of the current 4 above, over a SSB carrier for the likes of PSK-31, SSTV etc, or FM for the likes of Packet. So will the future be able to bring us anything new that will improve the usablility of radio? Doing a search on Google brings up thousands of hits, but none actually answer the questions, most also class each digital type as a mode. Would be very interested in your thoughts. If you do not feel this is the fourm to reply, a direct email to sparcnz(nospam)@gmail.com will be fine. (please remove the (nospam) before sending, I am trying to limit the amount of spam) Regards and thanks for looking at this thread. Kevin, ZL1KFM. <skype:sparc_nz?call> My status Get Skype <http://www.skype.com/go/download> and call me for free.
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