[Elecraft] [k3] NB & Chirp [+ general discussion of DSP vs. IF noise blanking]

[Duncan Carter]

Is the DSP blanker input level also subject to AGC?

Duncan, W5DC


Wayne Burdick wrote:
> Wes,
>
> The DSP NB causes some artifacts at its higher settings. This is an  
> unavoidable side effect of signal processing.
>
> The DSP NB is applied after the crystal filter, so the bandwidth is  
> already constrained, removing some of the inherent characteristics of  
> noise pulses, including their rise/fall time and shape. Thus it is  
> harder for the DSP to distinguish between signal and noise. On the  
> other hand, this is the only way to remove narrow-band noise (e.g.,  
> noise that appears every 10-15 kHz on a particular band, rather than  
> blanketing the entire band). The DSP NB also has the advantage of not  
> being "pumped" by distant signals outside the crystal filter.
>
> The IF NB has the opposite situation to contend with. Noise pulse  
> shape and rise/fall time are preserved, so they can be effectively  
> gated. But if you set the threshold too low, the IF NB's noise gate  
> can be modulated by very strong adjacent signals.
>
> By including both, we give the operator the ability to optimize the  
> ratio between IF and DSP blanking, which can be extremely effected as  
> attested to by many customers.
>
> 73,
> Wayne
> N6KR
>
> Wes Stewart wrote:
>
>   
>> Thanks Merv,
>>
>> So it isn't my imagination as some have inferred.
>>     
>
>
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