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Re: [TenTec] SDR-1000 vs Orion vs SDR-X

To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] SDR-1000 vs Orion vs SDR-X
From: "Geoffrey S. Mendelson" <gsm@mendelson.com>
Reply-to: gsm@mendelson.com,Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Tue, 18 Jul 2006 05:37:29 +0300
List-post: <mailto:tentec@contesting.com>
On Mon, Jul 17, 2006 at 09:23:06PM -0500, Stuart Rohre wrote:
> The other limitation at this time, are in the switching character of sound 
> cards, and thus true break in is a goal in the software radios.

I don't quite understand this, what is being switched? When VoIP became
popular, around 1998, the demand for full duplex sound cards caused half 
duplex (ones that needed to be switched) to disapear. 

It turned out that the most popular ones at the time, were Soundblasters,
which were always full duplex, but no one had bothered to write proper
drivers for them. Creative (the manufacturer) came out with a full duplex
Windows drivers. 

IMHO it makes no sense to "turn off" the soundcard when you are not
using it. From a hardware point of view, you need to protect the input
from overloading when the radio is transmitting anyway as far as software,
if you are not listening, you just discard the data. 

I'm not even sure that discarding the data is a good idea. If some of the
transmitted signal leaks into the receiver, it could cause feedback if
it makes it to the speaker, but if the output device is a pair of headphones,
you get an "air monitor". 

Do they "switch off" the soundcard to avoid problems with RF getting
into it?


Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com  N3OWJ/4X1GM
IL Voice: (07)-7424-1667  IL Fax: 972-2-648-1443 U.S. Voice: 1-215-821-1838 
Visit my 'blog at http://geoffstechno.livejournal.com/
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