K2 Realignment

[Jim Harris-4]

Last week I asked on this reflector about realigning
my K2 as it is about 10 months old and I wasn't really
sure I did a good job of it the first time.  Several
good people here on the reflector adviced it probably
was a good idea and offered some valuable suggestions
for this time around.  

Over the last two days I've spent about 10 hours doing
what I think is a good alignment and think that it is
now complete.  (Surprized how close most setting
were.)I've not done any serious on air testing with it
other than some casual listening because I have two
concerns.  Both relate to the IF passband as seen on
Spectrogram.  First, the CW level when using OP1
filter is about 20+ db higher than on LSB/USB.  If
this is a problem, any ideas as to how to correct it?
Second, the displayed bandwidth is 400-500 hz wider
than that set in the K2 and especially on OP1 which
was about 3khz+ wide.  They resemble their settings
except all are simply wider than that set.  I'm
allowing for half power points and all that. I had to
increase the Spectrogram sample rate to see all the
bandwidth especially on OP1.

Again my thanks to all for the good help I received
and to Elecraft for the bandwidth here.

Jim, AB0UK
K2/100 S/N 4787

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[Don Wilhelm-3]

Jim,

Where are you observing the 20+ dB difference between CW and SSB?
Spectrogram?, the S-meter?, or your ears?.
And I might also ask what audio frequencies are you setting the low and high
ends of the passband for the CW (and CWr) setting? - they should be quite
similar (or identical) to those you used for SSB - the audio response should
extend upward from 300 Hz to the end of the passband - literally 'centering'
a wide bandwidth on the CW sidetone pitch will result in a filter where you
can hear both sides of zero frequency, and that is not desirable (and will
cause a change in the S-meter response as well as the perceived audio
response).

If you have the BFOs set to the same frequency for CW as you have for SSB,
then there should be no difference in the receive signal path and therefore
no diference in the audio and S-meter response.  There may be a difference
in percieved audio if you have the KDSP2 installed and active, it's
characteristics are different for CW and SSB, especially if you have the
noise reduction turned on, or a difference in gain set in the KDSP.

Width of the filters - it is normal for the variable filter to be different
than the width indicated on the display - at wide settings, it is usually
wider (sometimes considerably) and it varies with the exact crystal set mix
that you have and tolerances on the varactors.  There is a footnote in the
manual indicating that the bandwidth numbers are a relative indication of
the filter width.  I usually find that the width is about correct near 400
Hz (which I understand to be the filter design point).

For the fixed OP1 filter to be off by more than a hundred Hz in bandwidth is
unusual.  The width is set by the capacitor values on the KSB2 board and I
rarely find that it varies from the nominal width.  With a 2.4 kHz width,
the normal passband extends from 300 Hz to 2700 Hz, and will be entirely
contained on the Spectrogram screen, however with the 2.6 kHz bandwidth, the
audio range extends from 300 Hz to 2900 Hz and the high end will be off the
default Spectrogram screen - you can set the Band(Hz) control in Spectrogram
for 200 to 2956  and contain both the 300 and 2900 Hz markers on the screen
without changing the FFT size or anything else.

73,
Don W3FPR

> -----Original Message-----
>
> Over the last two days I've spent about 10 hours doing
> what I think is a good alignment and think that it is
> now complete.  (Surprized how close most setting
> were.)I've not done any serious on air testing with it
> other than some casual listening because I have two
> concerns.  Both relate to the IF passband as seen on
> Spectrogram.  First, the CW level when using OP1
> filter is about 20+ db higher than on LSB/USB.  If
> this is a problem, any ideas as to how to correct it?
> Second, the displayed bandwidth is 400-500 hz wider
> than that set in the K2 and especially on OP1 which
> was about 3khz+ wide.  They resemble their settings
> except all are simply wider than that set.  I'm
> allowing for half power points and all that. I had to
> increase the Spectrogram sample rate to see all the
> bandwidth especially on OP1.
>
> Again my thanks to all for the good help I received
> and to Elecraft for the bandwidth here.
>
> Jim, AB0UK
> K2/100 S/N 4787
>
> __________________________________________________
> Do You Yahoo!?
> Tired of spam?  Yahoo! Mail has the best spam protection around
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>
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