[Elecraft] KDSP2 - SSB Gain

Sun Aug 10 13:34:00 2003

Thanks, Lyle.  That clarifies things completely.

best wishes,

dave

--On Sunday, August 10, 2003 8:33 AM -0700 Lyle Johnson 
<[email protected]> 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
>
>
>
>
>
>
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----------------------------------
David A. Belsley
Professor of Economics