KDSP2 and W3FPR fixed audio out, frequency rolloff

[Sjoerd-8]

Hello all,


I am using a W3FPR-like fixed audio out for my K2 for abt. 3 months now,
worked very well until now.

After installing my new KDSP2 the audio to the PC seems affected.
In the original setup the high frequency rolloff was abt. 2 dB from 400Hz to
2.6 KHz.
Now it is abt 6 dB over the same range.

Any suggestions how to compensate for this??
It looks like the output of the product detector is loaded different with
the KDSP2.

Any help would be appreciated!

Tnx in advance,

Sjoerd
PE2SVN

K2 #5095

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[Don Wilhelm-3]

Sjoerd,

If your fixed audio output is connected to the VOL1 and VOL2 signal lines
(as in my suggested connection points), then the KDSP2 is upstream of the
fixed audio output, and there should be no change in the loading of the
product detector due to the fixed audio output.  OTOH, if your fixed audio
output uses the PD1 and PD2 signals, then yes, you may have a different load
presented to the product detector - furthermore the KDSP2 will not provide
filtering for the fixed audio output when connected to PD1 and PD2.

One other comment - the KDSP2 (and KAF2) adds a low pass filter at all
times.  Could it possibly be the effects of that low pass filter that you
are seeing?  The cutoff is supposed to be higher, but you could have
something awry with the KDSP2 - set the KDSP2 to BYPASS to see if the
condition changes.

73,
Don W3FPR

> -----Original Message-----

>
> I am using a W3FPR-like fixed audio out for my K2 for abt. 3 months now,
> worked very well until now.
>
> After installing my new KDSP2 the audio to the PC seems affected.
> In the original setup the high frequency rolloff was abt. 2 dB
> from 400Hz to
> 2.6 KHz.
> Now it is abt 6 dB over the same range.
>
> Any suggestions how to compensate for this??
> It looks like the output of the product detector is loaded different with
> the KDSP2.
>
> Any help would be appreciated!
>
> Tnx in advance,
>
> Sjoerd
> PE2SVN
>
> K2 #5095
>
>

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[Sjoerd-8]

Hi Don,

Thanks for your reply.. i have tested the difference between PD1+2 and
VOL1+2, there is no difference in the signals.

I have put them back on PD1 and 2 to get a clean audio output, the PC will
provide DSP features, and the last I want is a disturbed signal in my PC.

I have also found that there is a 4 dB bump on the passband of the SSB
filter at abt 1 kHz.. Maybe a nice experiment for next weekend....

The K2 provides more experimenting fun than operating so far.. not really
sure what I like most....

73,

Sjoerd PE2SVN


-----Oorspronkelijk bericht-----
Van: Don Wilhelm [mailto:[hidden email]]
Verzonden: zondag 5 februari 2006 15:02
Aan: Sjoerd; Elecraft Reflector
Onderwerp: RE: [Elecraft] KDSP2 and W3FPR fixed audio out, frequency rolloff

Sjoerd,

If your fixed audio output is connected to the VOL1 and VOL2 signal lines
(as in my suggested connection points), then the KDSP2 is upstream of the
fixed audio output, and there should be no change in the loading of the
product detector due to the fixed audio output.  OTOH, if your fixed audio
output uses the PD1 and PD2 signals, then yes, you may have a different load
presented to the product detector - furthermore the KDSP2 will not provide
filtering for the fixed audio output when connected to PD1 and PD2.

One other comment - the KDSP2 (and KAF2) adds a low pass filter at all
times.  Could it possibly be the effects of that low pass filter that you
are seeing?  The cutoff is supposed to be higher, but you could have
something awry with the KDSP2 - set the KDSP2 to BYPASS to see if the
condition changes.

73,
Don W3FPR

> -----Original Message-----

>
> I am using a W3FPR-like fixed audio out for my K2 for abt. 3 months now,
> worked very well until now.
>
> After installing my new KDSP2 the audio to the PC seems affected.
> In the original setup the high frequency rolloff was abt. 2 dB
> from 400Hz to
> 2.6 KHz.
> Now it is abt 6 dB over the same range.
>
> Any suggestions how to compensate for this??
> It looks like the output of the product detector is loaded different with
> the KDSP2.
>
> Any help would be appreciated!
>
> Tnx in advance,
>
> Sjoerd
> PE2SVN
>
> K2 #5095
>
>

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