[Elecraft] eHam.net forum message

[Geoffrey Mackenzie-Kennedy]

Thanks for your explanation, I had missed the point of RLVZ's comment.

A related cause and I am speculating here without doing the calculations, 
when the noise is rough and signals are at or under the noise floor might be 
the added in-passband low level intermodulation products generated by a 
narrow bandwidth roofing filter when hit by all of the received noise power, 
which the DSP then has to cope with, given that the OIP3 of a narrow 
bandwidth crystal filter is usually "worse" than that of a wider filter - 
all else being equal. I do have some crystal filter OIP3 vs filter bandwidth 
measured data which shows this effect, but will stop speculating on the 
effect on a DSP :-)

I agree with your comment about DSP radios vs full analogue radios.

73,

Geoff
GM4ESD



Tom W8JI wrote:

> I think people are talking about two different things here.
>
> What I am talking about, and what I understand some others to be talking
> about, is a problem with DSP systems processing noise floor signal,
> especially when the noise is a bit rough, without adding artifacts that 
> make
> copy or quality worse.

<snip>

> I have no problem at all with how the K3 blanker and noise reduction 
> works,
> and actually IMO it does a good job for me. I just don't think any DSP 
> radio
> is as good as a full analog system when signal levels are near noise 
> levels,
> especially when the noise floor is a bit rough.