I can hear stations on other side of Zero beat

[g0kla]

Hi all,

I just finished building my K2 and it seems to be working well on receive.  However, I have noticed that I can hear CW stations on both sides of zero beat when using the widest (1.5kHz) filter setting.  It's not just a weakly audible signal for very strong 59+20 signals, which I would expect.  I can hear a 59 signal at S7 or S8.

With the 0.7kHz signal this is not the case, so I presume it is to do with the way that I have setup the filter and the BFO.  What have I done wrong?  Any ideas?  I set it up as per the instructions in the manual.

Chris
ac2cz
g0kla

[Don Wilhelm-4]

Chris,

There are 2 things 'wrong' which are contributing to your problem.
First, the varactors that have shipped recently have a greater
capacitance range than they used to - same type number, so 'go figure'.
The result is that the filter widths at the wider settings are
substantially wider than indicated by the K2 display - so the
recommended FL1 setting of 1.50 kHz may actually be as wide as 2.00
kHz.  The filters less than 1.00 width seem to be running about normal.
The second thing 'wrong' is a result of the first - the BFO settings in
the manual are no longer correct due to this change in the varactor
performance.

The cure is to use Spectrogram to set your filters.  Make sure you set
the wide CW filter off to one side of zero frequency on the Spectrogram
screen.  Spectrogram will allow you to measure the actual width of your
filters.
Take a look at the K2 Dila Calibration article on my website
www.w3fpr.com for information about using Spectrogram (part 3 is about
setting the filters).  The application is available for download from
Tom Hammond's website www.n0ss.net.

You will find a similar problem with the SSB filter set - the width is
much wider than indicated by the K2.  Spectrogram will give you the tool
to visually see this and make the proper adjustment.

73,
Don W3FPR

g0kla wrote:

> Hi all,
>
> I just finished building my K2 and it seems to be working well on receive.
> However, I have noticed that I can hear CW stations on both sides of zero
> beat when using the widest (1.5kHz) filter setting.  It's not just a weakly
> audible signal for very strong 59+20 signals, which I would expect.  I can
> hear a 59 signal at S7 or S8.
>
> With the 0.7kHz signal this is not the case, so I presume it is to do with
> the way that I have setup the filter and the BFO.  What have I done wrong?
> Any ideas?  I set it up as per the instructions in the manual.
>
> Chris
> ac2cz
> g0kla
>  

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[g0kla]

Thanks Tom and Don for helpful advice.  I will try Spectrogram to re-setup
the filters.  So far I just set them up using the data in the table in the
manual.

Chris
g0kla
ac2cz

On Tue, Aug 10, 2010 at 12:21 PM, Tom Hammond <[hidden email]> wrote:

> Hi Chris:
>
> What method did you use to adjust your BFO (XTAL FILTER) settings?
>
> If you have a PC available to use (even if only temporarily) with your K2,
> you might consider going to my web site and downloading Spectrogram v5.1.7
> and the written docs (immediately below the Spectrogram link) which
> specifically detail how to use Spectrogram to ACCURATELY adjust your BFOs
> so that the filters are working as well as possible.  That should address
> your
> problem.
>
> The ONLY 'additional' device you'll need will be an audio (monaural) cable
> to go from the K2 SPKR output to the MIC (or LINE) IN input on your PC.
>
> Spectrogram and the docs are available at:
>
>    Spectrogram:  http://www.n0ss.net/spectrogram517.exe
>  Documentation:  http://www.n0ss.net/k2_filters_using_gram_v5r17.pdf
>
> Shout if you need any help.
>
> Cheers,
>
> Tom Hammond   N0SS
>
>
> At 10:47 08/10/2010, you wrote:
>
>  Hi all,
>>
>> I just finished building my K2 and it seems to be working well on receive.
>> However, I have noticed that I can hear CW stations on both sides of zero
>> beat when using the widest (1.5kHz) filter setting.  It's not just a
>> weakly
>> audible signal for very strong 59+20 signals, which I would expect.  I can
>> hear a 59 signal at S7 or S8.
>>
>> With the 0.7kHz signal this is not the case, so I presume it is to do with
>> the way that I have setup the filter and the BFO.  What have I done wrong?
>> Any ideas?  I set it up as per the instructions in the manual.
>>
>> Chris
>> ac2cz
>> g0kla
>> --
>> View this message in context:
>> http://elecraft.365791.n2.nabble.com/I-can-hear-stations-on-other-side-of-Zero-beat-tp5393616p5393616.html
>> Sent from the Elecraft mailing list archive at Nabble.com.
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
>

--
Chris E. Thompson
[hidden email]
[hidden email]
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