It has been interesting to read the comments here on the list. I am
non-technical but hands on network peddler/engineer. I knew that work was
under way to get sub 5k vocoders but less that half!!?? WOW. I am sure
that the footprint required by the transport protocols (IP) are driving
this a lot.
I think I can hear quantizing noise on voice with the 5 k codecs, but the
7-8 k sound like "toll quality" to me. There is an edge to the audio on
the 5k voice. But it is perfectly usable. I guess the tape will move
downstream as the development continues.
BTW, our club had a presentation by a major AM station engineer on AM
digital radio. He had tapes that illustrated the "there/not there" quality
of digital audio. But they are really torturing the bandwidth to achieve a
compatible signal. He said has does not see any way to generate a legal
signal and have any adjacent channels because they are using the outside
sidebands for the digital information. That is why digital AM is confined
to daytime broadcast.."The times they are a changing"
John
WB1EHL
At 05:55 PM 2/17/04, you wrote:
Missed your reply. Incorrect time applied somewhere enroute.
Friend who attends standards meetings for codecs says 2kbps
by tokenizing speech components.
With 16QAM that's what 500Hz?
Competitive with high speed CW :-)
-Bob
John Graves wrote:
I am not good at the math but with G.723 you can get voice down to about
5 kbps without a wrapper. So with Quad modulation, what baud rate are we
looking at? Does that translate to a baud of 1.25 kbps?
Can't we get that into a 3khz window...That's all modems are looking into???
John
WB1EHL
At 03:24 PM 2/13/2004 -0500, tongaloa wrote:
It would be kind of fun to mess around with 6kc-10kc bandwidth digital
modes. Would take up no more space than the HiFi SSB. HF 16 QAM
anyone?
jhgraves@gis.net wrote:
Given the high level of concern for broadband SSB shown on the list
recently, I thought it resonable to make the following proposition. As
we all know, the width of a CW signal increases as a function of the
switching speed. Given that high speed CW is therefore occupying a
larger bandwidth that I at 5 wpm, should there not be some quiet corner
devoted solely to slow speed CW. We could then operate quietly and
efficiently, and feel good about only occupying a proper amount of
bandwidth.
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John Graves
Dynamic Devices, Inc.
781-245-9100
We make your data, data and voice, and data, voice and video
connections happen.... easily!
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