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Re: [TenTec] The QSK of SSB

To: "tentec@contesting.com" <tentec@contesting.com>
Subject: Re: [TenTec] The QSK of SSB
From: "Jim Brown" <jim@audiosystemsgroup.com>
Reply-to: Jim Brown <jim@audiosystemsgroup.com>,tentec@contesting.com
Date: Mon, 16 Aug 2004 13:53:51 -0500
List-post: <mailto:tentec@contesting.com>
On Mon, 16 Aug 2004 08:37:24 -1000, Ken Brown wrote:

>If the TX audio were digitized and then delayed, it would be possible 
>for the VOX to turn on the transmitter after the beginning of a word, 

For at least several decades, the designers of studio/broadcast quality 
devices like compressors and limiters have used "feed forward" 
techniques, whereby the audio path is delayed by a few ms but un-
delayed audio goes to the gain reduction element that provides the 
limiting. This alllows the limiting to be very transparent -- the gain is 
reduced a fraction of a ms before the peak hits it, so there is no 
overshoot.  

The very small delays needed to make VOX work without clipping 
leading edges would not be a problem in ham applications. The entire 
audio signal is still there, but is simply transmitted a 5-10 ms later, from 
beginning to end. 

Jim Brown  K9YC



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