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Multiple Ghost Image CW Decodes While Using CW Skimmer & a K3

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KC0W

Multiple Ghost Image CW Decodes While Using CW Skimmer & a K3

Been toying around with CW Skimmer, kinda an interesting program.

Anyway, I'm receiving multiple "ghost image" CW decodes from the same station while running Skimmer. They are 1 Kc or so apart from another. Better stated, the same stations signal is being shown on the horizontal waterfall numerous times. I have tried narrowing the K3's filters, reducing sound card audio into Skimmer & toyed around with every other parameter with no success.

Any ideas why I'm seeing the same station numerous times?

Tom KC0W

Julian, G4ILO

Re: Multiple Ghost Image CW Decodes While Using CW Skimmer & a K3

KC0W wrote

Been toying around with CW Skimmer, kinda an interesting program.

Anyway, I'm receiving multiple "ghost image" CW decodes from the same station while running Skimmer. They are 1 Kc or so apart from another. Better stated, the same stations signal is being shown on the horizontal waterfall numerous times. I have tried narrowing the K3's filters, reducing sound card audio into Skimmer & toyed around with every other parameter with no success.

Any ideas why I'm seeing the same station numerous times?

Is the separation of the ghosts a multiple of the audio frequency of the signal? Do the ghosts go away if you turn down the volume or use headphones? It might be microphony, which has been responsible for weak transmit spurii spaced by the frequency of the sidetone. There is a stiffener for the synthesizer board that is supposed to cure the problem (if that's what it is.)

Julian, G4ILO. K2 #392 K3 #222 KX3 #110
* G4ILO's Shack - http://www.g4ilo.com
* KComm - http://www.g4ilo.com/kcomm.html
* KTune - http://www.g4ilo.com/ktune.html

Brett Howard

Re: Multiple Ghost Image CW Decodes While Using CW Skimmer & a K3

In reply to this post by KC0W

What do you have your Line out setting set to? Do they get better as
you turn the Line out level down and turn up the line in level on the
PC?

~Brett (N7MG)

On Sun, Feb 27, 2011 at 7:54 AM, KC0W <[hidden email]> wrote:

> Been toying around with CW Skimmer, kinda an interesting program.
>
> Anyway, I'm receiving multiple "ghost image" CW decodes from the same
> station while running Skimmer. They are 1 Kc or so apart from another.
> Better stated, the same stations signal is being shown on the horizontal
> waterfall numerous times. I have tried narrowing the K3's filters, reducing
> sound card audio into Skimmer & toyed around with every other parameter with
> no success.
>
> Any ideas why I'm seeing the same station numerous times?
>
>
>
> Tom KC0W
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/Multiple-Ghost-Image-CW-Decodes-While-Using-CW-Skimmer-a-K3-tp6070469p6070469.html
> Sent from the Elecraft mailing list archive at Nabble.com.
> ______________________________________________________________
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kk7uq

Re: Multiple Ghost Image CW Decodes While Using CW Skimmer & a K3

In reply to this post by Julian, G4ILO

Hi Tom

SNIP
-----------------------
Been toying around with CW Skimmer, kinda an interesting program.

Anyway, I'm receiving multiple "ghost image" CW decodes from the same
station while running Skimmer. They are 1 Kc or so apart from another.
Better stated, the same stations signal is being shown on the horizontal
waterfall numerous times. I have tried narrowing the K3's filters, reducing
sound card audio into Skimmer & toyed around with every other parameter with
no success.
------------------------

I have seen the same thing on strong signals displayed on CW Skimmer. On DX Skimmer, I can see the same signal at 3x the pitch frequency. I can not see it on the waterfall view of the spectrum from MixW which is running at the same time. This particular signal was running 50 dB above noise level and harmonics were not visible in either the MixW spectrum or waterfall display.

If I increase the audio output level from the interface to the point where there is clipping in the audio coming from the interface, I can see the signal at 2x, 3x and more on the skimmer waterfall, but can only see the 3x signal on the MixW waterfall.

Try reducing your audio drive into the soundcard input to be sure a strong signal is not clipping there, and then see if the multiple copies go away. CW Skimmer does it's own AGC so it can operate well with reduced audio levels.

73, Clint KK7UQ

Guy, K2AV

Re: Multiple Ghost Image CW Decodes While Using CW Skimmer & a K3

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.

On Mon, Feb 28, 2011 at 1:53 PM, kk7uq <[hidden email]> wrote:

> Hi Tom
>
> SNIP
> -----------------------
> Been toying around with CW Skimmer, kinda an interesting program.
>
> Anyway, I'm receiving multiple "ghost image" CW decodes from the same
> station while running Skimmer. They are 1 Kc or so apart from another.
> Better stated, the same stations signal is being shown on the horizontal
> waterfall numerous times. I have tried narrowing the K3's filters, reducing
> sound card audio into Skimmer & toyed around with every other parameter
> with
> no success.
> ------------------------
>
> I have seen the same thing on strong signals displayed on CW Skimmer. On
> DX
> Skimmer, I can see the same signal at 3x the pitch frequency. I can not
> see
> it on the waterfall view of the spectrum from MixW which is running at the
> same time. This particular signal was running 50 dB above noise level and
> harmonics were not visible in either the MixW spectrum or waterfall
> display.
>
> If I increase the audio output level from the interface to the point where
> there is clipping in the audio coming from the interface, I can see the
> signal at 2x, 3x and more on the skimmer waterfall, but can only see the 3x
> signal on the MixW waterfall.
>
> Try reducing your audio drive into the soundcard input to be sure a strong
> signal is not clipping there, and then see if the multiple copies go away.
> CW Skimmer does it's own AGC so it can operate well with reduced audio
> levels.
>
> 73, Clint KK7UQ
>
>
> --
> View this message in context:
> http://elecraft.365791.n2.nabble.com/Multiple-Ghost-Image-CW-Decodes-While-Using-CW-Skimmer-a-K3-tp6070469p6074435.html
> Sent from the Elecraft mailing list archive at Nabble.com.
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

kk7uq

Re: Multiple Ghost Image CW Decodes While Using CW Skimmer & a K3

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.
----------------------

KD8NNU

Re: Multiple Ghost Image CW Decodes While Using CW Skimmer & a K3

In reply to this post by KC0W

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.
> ----------------------
>
>
> --
> View this message in context:
> http://elecraft.365791.n2.nabble.com/Multiple-Ghost-Image-CW-Decodes-While-Using-CW-Skimmer-a-K3-tp6070469p6074752.html
> Sent from the Elecraft mailing list archive at Nabble.com.
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

Don Wilhelm-4

Re: Multiple Ghost Image CW Decodes While Using CW Skimmer & a K3

Don,

It is not likely that the ghost images are coming from the K3 itself, so
narrow roofing filters are not likely to help.

The ghost images normally are associated with something in the audio
chain of whatever is connected to the K3. Soundcard amplitude problems
(overdrive), or just plain "cheap" soundcards. The other potential
problem is the transformers in the K3. They can create some distortion
if the Line Out gain is set greater than 10.

So check the K3 Line Out gain setting, and if the ghosts are still
present, suspect clipping or overload of the computer soundcard.

I wish you luck in determining which of the many variables is causing
your conditions. There are no immediate and precise answers - it is
more of a "guessing game" and you have to check out each "guess".

73,
Don W3FPR

On 2/28/2011 8:22 PM, [hidden email] wrote:

> 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
>
>