[TenTec] OmniV and PSK31 -- any experience to be shared??

[Jim Brown K9YC]

On Wed, 19 Mar 2008 10:56:39 -0400, Mark Erbaugh wrote:

>I hadn't thought of it as a "headroom" issue. The main point is that a
>PSK31 signal cannot tolerate any non-linear amplification.  Actually,
>the intelligence still gets through, but the signal is badly distorted
>and takes up unnecessary bandwidth. 

That is exactly right.  It is the basis of my recommendations that 1) the 
sound card run so that the output level is at least 3 dB below clip, which 
reduces the distortion produced by the sound card; and 2) a simple 
resistive divider of 20 dB (10:1 resistance ratio) is added between the 
sound card and the radio (this prevents overload distortion in the radio's 
input stage).  Set the radio to do no processing, THEN set audio drive in 
the radio and the output power as recommended for "keydown" modes like PSK 
and RTTY modes, typically 30-50 watts in a 100w radio. This ALSO reduces 
IM distortion in most radios, and it prevents overheating the radio.

BTW -- I'm a pro audio guy, and have worked in pro audio and broadcasting 
since 1960. 

73,

Jim K9YC