K3 #1456 - data modes setup

[Bob Towers-2]

I tried connecting LINE IN and LINE OUT to the on-board soundcard
(Realtek ALC883) on my PC and the problem now appears to be solved.

LINE OUT level is now 13 and the MIC (LINE IN) level is now 30, which
looks about right. Well, right enough for my first PSK31 contacts with
EU stations on 30m. I was running about 5W.

I can only assume that the input and output levels on the Aureal Vortex
PCI card are too low for the K3.

73

Bob MM0RKT
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[Mike Scott-7]

>I need to set the K3 LINE OUT level well above 50 before I
can see a trace on MixW's waterfall, even with the soundcard's line in
level set to maximum.

Bob, some of us have measured distortion on the line out connection on our
K3s and find that it is significant on high line-out drive levels. I think
the manual suggests nothing higher than 10. Mine has noticeable artifacts on
a waterfall with a single tone RF input from an XG2 signal generator with
any line-out gain setting above 3. Luckily that is just enough to drive my
internal soundcard, YMMV.


Mike Scott - AE6WA

Tarzana, CA (DM04 / near LA)
K3-100 #508/ KX1  #1311


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[Joe Subich, W4TV-3]

> Bob, some of us have measured distortion on the line out
> connection on our K3s and find that it is significant on high
> line-out drive levels. I think the manual suggests nothing
> higher than 10.

The Line Out level is not an absolute voltage - it represents
a general gain setting.  You will find that the distortion is
based on absolute audio signal voltage.  As long and Line Out
remains below roughly 1V peak (about .8V RMS) distortion levels
will be minimal.  

The specific Line Out setting will depend on your particular
AGC settings.  If AGC is off, an S9 signal (XG1/XG2, etc.)
will generate 1V peak with Line Out as low as 3 or 4.  If the
AGC is on, the 1V point will depend on threshold and slope.  With
the highest AGC SLP settings (maximum output flatness), Line Out
can be advanced to nearly maximum before the output reaches 1 volt.  

73,

   ... Joe, W4TV
 

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Mike Scott
> Sent: Thursday, August 28, 2008 7:14 AM
> To: [hidden email]
> Subject: Re: [Elecraft] K3 #1456 - data modes setup
>
>
>
> >I need to set the K3 LINE OUT level well above 50 before I
> can see a trace on MixW's waterfall, even with the
> soundcard's line in
> level set to maximum.
>
> Bob, some of us have measured distortion on the line out
> connection on our K3s and find that it is significant on high
> line-out drive levels. I think the manual suggests nothing
> higher than 10. Mine has noticeable artifacts on a waterfall
> with a single tone RF input from an XG2 signal generator with
> any line-out gain setting above 3. Luckily that is just
> enough to drive my internal soundcard, YMMV.
>
>
> Mike Scott - AE6WA
>
> Tarzana, CA (DM04 / near LA)
> K3-100 #508/ KX1  #1311
>

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[Jim Brown-10]

On Thu, 28 Aug 2008 10:51:57 -0400, Joe Subich, W4TV wrote:

> As long and Line Out
>remains below roughly 1V peak (about .8V RMS) distortion levels
>will be minimal.  

Not quite. Because most of the distortion is caused by the
transformer, distortion rises rapidly with decreasing frequency
(that's the nature of transformers at the limits of their ratings).
If you're running RTTY at narrow bandwidths, using 2.2 kHz tones,
and paying attention to the AGC considerations noted below, you're
not likely to have problems at this level. But if you're running
PSK31 with a typical wideband filter, the low frequency components
(static, noise, other signals) could produce enough distortion to
degrade operation of the PSK decoder (in the computer sound card).

>The specific Line Out setting will depend on your particular
>AGC settings.  If AGC is off, an S9 signal (XG1/XG2, etc.)
>will generate 1V peak with Line Out as low as 3 or 4.

Yes.

Jim Brown K9YC



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[Joe Subich, W4TV-3]

> But if you're running
> PSK31 with a typical wideband filter, the low frequency components
> (static, noise, other signals) could produce enough distortion to
> degrade operation of the PSK decoder (in the computer sound card).

Operating narrow band modes with wideband receivers is not good
engineering practice.  If AGC is disabled the receiver and audio
(soundcard gains) need to be backed off sufficiently to prevent
overload with strong undesired signals.  This give up dynamic range
on weak signals.  If AGC in enabled, strong undesired signals will
activate the AGC and reduce gain - often to the point of blocking
the weak signal.  

Narrow receiver filtering makes a big difference and protects the
audio circuits from the unnecessary LF energy.

As long as the user does not "push" the IF response below the K3
standard 200 Hz low cut, the LF energy is not a significant issue.
A 1V peak tone at 250 Hz has harmonic distortion at -78 dB (2nd),
-49 dB (3rd), -81 dB (4th) and -65 dB (5th).  The 2nd and 4th
harmonics may be lower as the measured values are the noise floor.
Although those numbers are slightly worse than at 500 Hz or 1 KHz,
-50 dB distortion levels are more than adequate for narrow band
reception.

By the way, in order to get 1V Line Out levels with an XG2 (preamp
on), I found it necessary to disable AGC or set the slope below 10.
With AGC and slope settings used by most users, maximum Line Out
will not generate a 1V Peak signal for S9 inputs.  With AGC, setting
Line Out as high as 25 results in maximum audio levels at -15 to -20
dBu which allows sufficient headroom before the onset of distortion.

73,

   ... Joe, W4TV
 

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Jim Brown
> Sent: Thursday, August 28, 2008 11:46 AM
> To: [hidden email]
> Subject: RE: [Elecraft] K3 #1456 - data modes setup
>
>
> On Thu, 28 Aug 2008 10:51:57 -0400, Joe Subich, W4TV wrote:
>
> > As long and Line Out
> >remains below roughly 1V peak (about .8V RMS) distortion levels
> >will be minimal.  
>
> Not quite. Because most of the distortion is caused by the
> transformer, distortion rises rapidly with decreasing frequency
> (that's the nature of transformers at the limits of their ratings).
> If you're running RTTY at narrow bandwidths, using 2.2 kHz tones,
> and paying attention to the AGC considerations noted below, you're
> not likely to have problems at this level. But if you're running
> PSK31 with a typical wideband filter, the low frequency components
> (static, noise, other signals) could produce enough distortion to
> degrade operation of the PSK decoder (in the computer sound card).
>
> >The specific Line Out setting will depend on your particular
> >AGC settings.  If AGC is off, an S9 signal (XG1/XG2, etc.)
> >will generate 1V peak with Line Out as low as 3 or 4.
>
> Yes.
>
> Jim Brown K9YC
>
>
>
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[Julian, G4ILO]

Mike Scott-7 wrote

Bob, some of us have measured distortion on the line out connection on our
K3s and find that it is significant on high line-out drive levels. I think
the manual suggests nothing higher than 10. Mine has noticeable artifacts on
a waterfall with a single tone RF input from an XG2 signal generator with
any line-out gain setting above 3. Luckily that is just enough to drive my
internal soundcard, YMMV.

I noticed "ghost" CW signals at a multiple of the audio frequency, using CW Skimmer, when the line out setting was set above 2. It was only noticeable when using narrow filters, so the noise level at the frequency where the spurious signal fell was very low. It even confused CW Skimmer, copying the same call on two different frequencies.

When the filter bandwidth was opened up, as I imagine most people using Skimmer would do, band noise masked the "ghosts".

Cw Skimmer is very sensitive and will work at a low audio level. Other sound card programs really need a line out level of 10 or more.

I don't have measuring equipment so I have been unable to determine whether the fault is in the K3 or the on-board Realtek sound chip in my shack PC, but it does warrant further investigation.

[Alexandr Kobranov]

Maybe only short reminder - "ghosts" are surely from K3 as the same
signal with the same audio level to the same card was without "ghosts"
when delivered from other RIG. (TS-850 in my case)
Hope it was registered in Elecraft.
(Why "ghosts" and not only "harmonic distorsion"? - There are reported
PSK31 ghosts readable/detectable as valid PSK signals so it in not
non-linear harmonics behaviour...imho)

73!
L. -dst-

Julian, G4ILO napsal(a):

>
>
> Mike Scott-7 wrote:
>>
>> Bob, some of us have measured distortion on the line out connection on our
>> K3s and find that it is significant on high line-out drive levels. I think
>> the manual suggests nothing higher than 10. Mine has noticeable artifacts
>> on
>> a waterfall with a single tone RF input from an XG2 signal generator with
>> any line-out gain setting above 3. Luckily that is just enough to drive my
>> internal soundcard, YMMV.
>>
>>
>
> I noticed "ghost" CW signals at a multiple of the audio frequency, using CW
> Skimmer, when the line out setting was set above 2. It was only noticeable
> when using narrow filters, so the noise level at the frequency where the
> spurious signal fell was very low. It even confused CW Skimmer, copying the
> same call on two different frequencies.
>
> When the filter bandwidth was opened up, as I imagine most people using
> Skimmer would do, band noise masked the "ghosts".
>
> Cw Skimmer is very sensitive and will work at a low audio level. Other sound
> card programs really need a line out level of 10 or more.
>
> I don't have measuring equipment so I have been unable to determine whether
> the fault is in the K3 or the on-board Realtek sound chip in my shack PC,
> but it does warrant further investigation.
>
> -----
> Julian, G4ILO. K2 #392  K3 #222.
> http://www.g4ilo.com/ G4ILO's Shack   http://www.ham-directory.com/ Ham
> Directory    http://www.g4ilo.com/kcomm.html KComm for Elecraft K2 and K3

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