[Elecraft] KDSP2 - SSB Gain

[Baker]

On Sun, 10 Aug 2003 08:33:31 -0700, Lyle Johnson wrote:
>Hello Stewart!
>
>>When the DSP was switched ON with SSB Filter gain set to the
>>default
>>( 0 dB) the audio level went up by about 3.5 dB. No wonder=
 signals
>>sounded stronger !
>>
>>I have set the SSB filter gain to -3.5 dB and now observe no=
 change
>>in audio level between DSP in or out.
>>
>>I am wondering if my K2/DSP has a problem as I would have=
 expected
>>unity gain with the default setting of 0 dB.
>
>The short answer: it's normal.
>
>The long answer...
>
>The KDSP2 has an insertion loss of about 3 dB.  This is due to=
 the
>voltage
>divider at its input consisting of resistors R15 and R16 and=
 the
>input
>impedance of the A/D converter within the CODEC chip=
 (TLV320AIC23)
>on the
>DSPx module.
>
>In bypass mode, the CODEC acts as a switch, and simply passes=
 its
>input to
>its output.  In this case, the insertion loss is present.
>
>When you make the DSP active, approximately 3 dB of gain is=
 added
>back in to
>the system to overcome the insertion loss.  Thus, the 0.0 dB=
 gain
>setting is
>referenced to having no KDSP2 installed, rather than being
>referenced to the
>KDSP2 in bypass mode.
>
>73,
>
>Lyle KK7P
>
>
Lyle,

Thank you for the explanation. My findings now make sense.

In Bypass mode loss of 3 dB in audio power I find most=
 noticeable.

It seems a shame that any K2 module introduces an "OFF" insertion=
 
loss when fitted, but I guess that's the way of the world.

73

Stewart G3RXQ
>
>
>
>
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