[Elecraft] Multiple Ghost Image CW Decodes While Using CW Skimmer & a K3

[goldtr8 at charter.net]

Interesting I get ghost images when I create an artifical filter via dsp 
that I see in DM780.  My IF is a 2.1k and I am cranking down to 500hz or 
less for some of the modes.

Maybe I need an additional IF at 500 to 700 hz?

Don
KD8NNU


On Mon, Feb 28, 2011 at 3:23 PM, kk7uq wrote:

> Hello Guy
>
> I agree that the 3x signal is caused by clipping.  I had to really 
> raise the
> signal up to get it to show up.  If I set the noise baseline at -80 to 
> -60
> dB, the harmonic does not show up.  It looks like if the signal peak 
> goes
> higher than -20 dB on the MixW waterfall, the 3x starts to show up on 
> DX
> Skimmer, but still is not seen on the MixW waterfall.  I have to 
> increase
> the signal even more to the point where the signal is just below 0 dB 
> to see
> the 3x signal on the MixW waterfall.
> I have tried with the AGC on and off, with about the same results re: 
> where
> DX Skimmer shows it.
>
> The bottom line is keep your sound system adjusted so that the noise
> baseline is under -60 db, with AGC on, and you will not see these 
> extra
> signals.  The easiest way to adjust this is to use another program 
> such as
> MixW in the spectrum display mode to see where the noise baseline is, 
> and
> how strong the signal can get when AGC is on.  I am seeing AGC kicking 
> in
> when the strongest signal is about 30 dB above noise.
>
> 73, Clint
> KK7UQ
>
> Snip
> ---------------------
> 3 X the sound frequency sounds like sound card over-drive, or simply
> exceeding the actual linear range of the sound card.  On-board sound 
> chips
> and cheep Chinese sound cards are particularly vulnerable to showing
> odd-order effects if you look way down.  Those can sometimes be
> significantly improved by managing the range of input sound and 
> line-in
> levels.
> If you want to see a clean 100 dB range in audio devices, you will 
> have to
> get a high-end audio card.  The cheep stuff just doesn't go there.
>
> 73, Guy.
> ----------------------
>
>
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