[DSP-10] New Version 3.17 for DSPx

[Bob Larkin]

Hi Bob,

Thanks much for the report.  I have heard this also.  It is a result of the 
lower noise of the ADC in the DSPx!

I balanced the gain up for the EZ-Kit, and the noise input is lower for the 
DSPx. Both now use the same software, except for the CODEC differences. 
Certain audio filters end up with insufficient noise input and start 
showing quantization noise on the output. This is worse with AGC, because 
of different gain distribution in the DSP.  It is also worse if you back 
off the RF gain while receiving noisy signals.  The really narrow filters 
also have a lot of this since they filter out much of the noise. 
It  shouldn't be a problem if there is gain ahead of the radio from a 
transverter, or preamp.

High on my list is to redo the gain distribution for the DSPx, including 
adding control of the RF/IF gain as part of the AGC. This will also add 40+ 
dB of  signal range within the IF filter.  This should fix the DSPx 
quantization noise problems.

The quantization noise is really offensive to the ear!

73,. Bob W7PUA


At 12:47 PM 3/19/2004, you wrote:
>Hi,
>
>I experimented  a bit more with the new software.
>
>Discovered that the Ringing on the USB mode with the filter off goes away
>when the AGC is turned off.
>
>Hope this helps
>
>73,
>
>Bob Johansen WB2SRF
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