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Re: K3: DSP NR for Data A mode?

Posted by Bill Frantz on Jul 20, 2012; 9:57pm
URL: http://elecraft.85.s1.nabble.com/K3-DSP-NR-for-Data-A-mode-tp7559524p7559556.html

Note that NR is not available in DATA A mode -- K3 manual p25:
"NR turns noise reduction on. It doesn’t apply to DATA or FM
modes, or with AGC turned off."

Ray identified why I would like the K3 NR to work in DATA A when
he said, "NR algorithms -need- a broad "chunk" of spectrum". If
the DSP NR could work on a broad spectrum before filtering it
would have enough data to separate signal from noise. I'm not
trying to get NR to deal with strong nearby signals, but when I
narrow the bandwidth to get rid of them, my post-narrowing NR no
longer works so I'm looking for pre-narrowing NR.

I have used the notch filter, but it takes time to deploy, and
can't deal with two separate loud signals. By experience,
narrowing the DSP bandwidth is operationally easier and more effective.

I suppose I should bite the bullet and get a 24 bit USB "sound
card". Does anyone have any recommendations?

[It hurts to spend money for a 24 bit A/D converter which is
going to convert analog the radio has produced using a 24 bit
D/A converter. It's just unaesthetic.]

Cheers - Bill, AE6JV

On 7/20/12 at 10:43, [hidden email] (N5GE) wrote:

>Have you tried using a narrower filter in the K3 or using the K3 NR?

On 7/20/12 at 11:11, [hidden email] (Ray Sills) wrote:

>Well, the way I see it.... Noise Reduction won't help you get
>rid of strong nearby (in frequency and/or QTH) signals.  That
>would be the job of a notch filter.  In fact, I think NR
>algorithms -need- a broad "chunk" of spectrum, so as to be able
>to identify what is "signal" and what is "noise".  If you
>narrow the DSP bandwidth, the software many not have enough
>noise to work with.
>
>If those strong signals are overloading the A/D converter, you
>would be better off lowering the level fed to the converter.  I
>think the SignaLink uses a 16 bit converter, and this is where
>a 24 bit converter would work much better, since it has 24 dB
>more dynamic range (before clipping).

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