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K2 Filter Question

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Curt

K2 Filter Question

I completed K2 s/n06424 about two years ago, the only option is the KSB2,
rarely used. The filters are OP1, 0.7, 0.4, and 0.1 The 0.7 and 0.4
filters seem to exhibit what seems to me to be excessive signal attenuation.
Strangely, this doesn't seem to be the case for the 0.1 filter. This has
always been true since the unit was completed. Am wondering if somehow the
passband is off.

Any advice would be appreciated.

73, Curt KB5JO

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Don Wilhelm-4

Re: K2 Filter Question

Curt,

I suspect that your filter center frequencies are off.

Try using Spectrogram. That will display not only the filter center
frequencies, but also the amplitude.
If your K2 is typical, change the 0.10 filter to 0.20. The filter width
does not chance appreciably at widths less than 0.20, but the
attenuation does increase.

If you do not have Spectrogram, it can be downloaded from www.n0ss.net,
and Tom has several documents dealing with how to set up Spectrogram on
your computer.

Also take a look at my website www.w3fpr.com article dealing with K2
Dial Calibration. Part 3 of that article deals with filter setup.

73,
Don W3FPR

On 10/13/2010 9:06 PM, Curt wrote:

> I completed K2 s/n06424 about two years ago, the only option is the KSB2,
> rarely used. The filters are OP1, 0.7, 0.4, and 0.1 The 0.7 and 0.4
> filters seem to exhibit what seems to me to be excessive signal attenuation.
> Strangely, this doesn't seem to be the case for the 0.1 filter. This has
> always been true since the unit was completed. Am wondering if somehow the
> passband is off.
>
> Any advice would be appreciated.
>
> 73, Curt KB5JO
>
>
> ______________________________________________________________
> 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
>

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Curt

Re: K2 Filter Question

Thanks Don,

If the center frequencies were off, what would be the behavior tuning
through a CW signal? As I tune through a signal, the highest strength
happens about halfway through the respective width, at an audible frequency
that beats with the sidetone frequency in "spot". I would think if the
center were off, then the maximum would happen somewhere away from the
center frequency.

73, Curt KB5JO

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Don Wilhelm-4

Re: K2 Filter Question

Curt,

You observations are likely to be correct, but I would check the
centering using Spectrogram or similar just in case your audio "ears"
are not telling you the whole story.

For instance, if you have a bad crystal in the variable IF filter, there
would be some variation in the filter passband and that would lead you
to erroneous conclusions about the filter performance.

73,
Don W3FPR

On 10/13/2010 10:08 PM, Curt wrote:

> Thanks Don,
>
> If the center frequencies were off, what would be the behavior tuning
> through a CW signal? As I tune through a signal, the highest strength
> happens about halfway through the respective width, at an audible frequency
> that beats with the sidetone frequency in "spot". I would think if the
> center were off, then the maximum would happen somewhere away from the
> center frequency.
>
> 73, Curt KB5JO
>