kx1 audio filter

[Hrafnkell Eiríksson]

Hi

I was just checking up the audio filter bandwidth and attenuation when
changing the bandwidth on my KX1. I used the NGEN noise generator and
fed the audio output to my soundcard and analyzed with Spectrogram.

The bandwidth changes what seems to be correct when I change the
filter from wide to narrow but the output level drops over 10dB. Is
that normal?'

I assume this list doesn't accept attachment so I've put the
screenshots of my spectrogram display up at
http://tf3hr.he.klaki.net/files/tf3hr_kx1_narrow_filter.PNG
http://tf3hr.he.klaki.net/files/tf3hr_kx1_wide_filter.PNG

Thanks
  Hrafnkell Eiriksson TF3HR
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[Don Wilhelm-3]

Some attenuation at the extreme narrow end of the filter range is normal.
At slightly wider bandwidths, there is not much attenuation compared to
wider bandwidths.

This is a 3 crystal IF filter, rather than an audio filter.  The bandwidth
is controlled by the varactors.  I am not certain of the center design
point, but I would guess that it is in the range of 600 Hz bandwidth.  At
filter widths much more narrow than the design point, some attenuation is to
be expected, and at extremely wide bandwidths, the passband ripple may
become extreme.  Given its simplicity, the filter works quite well and
achieves a lot of versatile performance in a small package.

73,
Don W3FPR

> -----Original Message-----
>
> I was just checking up the audio filter bandwidth and attenuation when
> changing the bandwidth on my KX1. I used the NGEN noise generator and
> fed the audio output to my soundcard and analyzed with Spectrogram.
>
> The bandwidth changes what seems to be correct when I change the
> filter from wide to narrow but the output level drops over 10dB. Is
> that normal?'
>
> I assume this list doesn't accept attachment so I've put the
> screenshots of my spectrogram display up at
> http://tf3hr.he.klaki.net/files/tf3hr_kx1_narrow_filter.PNG
> http://tf3hr.he.klaki.net/files/tf3hr_kx1_wide_filter.PNG
>
> Thanks
>   Hrafnkell Eiriksson TF3HR

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[Hrafnkell Eiríksson]

Hi Don

Thanks for your quick reply. Yes ofcourse the filter is the IF filter.
So the extra 10dB attenuation of the signal in the passband is normal
at the narrow setting?

Thanks es 73 de TF3HR Hrafnkell Eiriksson

On 8/24/06, Don Wilhelm <[hidden email]> wrote:

> Some attenuation at the extreme narrow end of the filter range is normal.
> At slightly wider bandwidths, there is not much attenuation compared to
> wider bandwidths.
>
> This is a 3 crystal IF filter, rather than an audio filter.  The bandwidth
> is controlled by the varactors.  I am not certain of the center design
> point, but I would guess that it is in the range of 600 Hz bandwidth.  At
> filter widths much more narrow than the design point, some attenuation is to
> be expected, and at extremely wide bandwidths, the passband ripple may
> become extreme.  Given its simplicity, the filter works quite well and
> achieves a lot of versatile performance in a small package.
>
> 73,
> Don W3FPR
>
>
> > -----Original Message-----
> >
> > I was just checking up the audio filter bandwidth and attenuation when
> > changing the bandwidth on my KX1. I used the NGEN noise generator and
> > fed the audio output to my soundcard and analyzed with Spectrogram.
> >
> > The bandwidth changes what seems to be correct when I change the
> > filter from wide to narrow but the output level drops over 10dB. Is
> > that normal?'
> >
> > I assume this list doesn't accept attachment so I've put the
> > screenshots of my spectrogram display up at
> > http://tf3hr.he.klaki.net/files/tf3hr_kx1_narrow_filter.PNG
> > http://tf3hr.he.klaki.net/files/tf3hr_kx1_wide_filter.PNG
> >
> > Thanks
> >   Hrafnkell Eiriksson TF3HR
>
>

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