[K2} Xtal filter calibration numbers

[bdenley]

The K2 manual and the SSB option manual urge builders to save the xtal
calibration numbers written on the envelops they came in with the statement
that those numbers will be useful later for filter calibration.  But I don't
see where these numbers ever get used.  Has anyone else actually used those
numbers?
Brian
http://home.comcast.net/~b.denley/index.html 

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[Geoffrey Mackenzie-Kennedy]

Brian,

No, I have never used this xtal reference number.

The envelope containing the containing the xtals that came with my K2/100 #
3255 kit in 2003 was marked 7. My guess is that either Elecraft might have
changed their procurement spec for the xtals from time to time, and the
number was used to identify the xtals procured using a paticular version of
the spec, OR more likely, if they did not change the procurement spec the
xtals purchased were sorted into different groups of matched sets, and the
number was used to identify the particular series resonant frequency of the
matched set of xtals supplied in any one kit. But I am guessing.

The frequency spread of similar computer grade xtals can be quite large, to
get 10 reasonably well matched xtals of this grade for use in a filter one
usually has to buy at least 50.

73,
Geoff
GM4ESD


Brian Denley wrote on Thursday, August 19, 2010 at 4:34 AM:

> The K2 manual and the SSB option manual urge builders to save the xtal
> calibration numbers written on the envelops they came in with the
> statement
> that those numbers will be useful later for filter calibration.  But I
> don't
> see where these numbers ever get used.  Has anyone else actually used
> those
> numbers?
> Brian


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[Don Wilhelm-4]

Brian,

For the SSB option - yes, that number can be used to set the BFO
frequency to the value listed in the KSB2 manual and will produce a
workable filter setting for SSB OP1 filter (with a 2.4 kHz width).

There is no similar chart for the basic K2.  Add to that the fact that
the varactor characteristics have changed recently (same type number,
different characteristics, but usable), and the wide filter widths
(those above 1.00) can be much wider than indicated by the K2 display
and make the use of Spectrogram or other audio spectrum display
application be used to properly set the width of these wide filters (the
SSB filters and CW FL1).  This situation is present in K2s sold over the
last couple years - for older K2s the displayed width and the actual
filter widths track nicely.  Fortunately, when the filter width is at
the more normal CW widths, the tracking is still quite good, so the
default settings work OK.  To obtain optimum settings, it is still
necessary to either have an ear that will detect pitch quite well or use
Spectrogram or other to set the BFOs.

In short, do not believe the filter widths greater than 1.00 in K2s
having serial numbers above 6000, but use a tool to measure the actual
filter width.  I have seen cases where a width setting of 2.00 produced
a filter that was in excess of 3 kHz wide.

73,
Don W3FPR

Brian Denley wrote:
> The K2 manual and the SSB option manual urge builders to save the xtal
> calibration numbers written on the envelops they came in with the statement
> that those numbers will be useful later for filter calibration.  But I don't
> see where these numbers ever get used.  Has anyone else actually used those
> numbers?
> Brian
> http://home.comcast.net/~b.denley/index.html 
>
>  
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