[Elecraft] N0SS CW Filter Alignment

[Rich Lentz]

These readings were taken with MixW 2 using WWV CARRIER (did not use the
periodic tone) as a reference.  As I recall, the carrier was about 7 Hz
high (10,000,007 Hz) when I started collecting the data which is
provided as REF.  WWV at 5 MHz and the Russian standard at 14.996 MHz
was also very close to about 7 Hz high.  

The table shows the difference from this reference value (all values
were taken at 10 MHZ though) and only several were filters were checked
at other frequencies and they were comparable.  Thus, using USB and FL4
I was reading 9,999,997 instead of 10,000,000. All LSB filters were
right on top of each other (no shift) and all were reading 10,000,007
(+/- a decimal point).  However, the trace from the waterfall did not
move.   The table only shows the difference in Hz so that I did not have
to write a table with 8/9 digits.

The reason I used MixW is so that I can see the shift in the colored
trace. With the waterfall expanded to X3 or X4 you can get very accurate
readings of the frequency, in the decimal points even though they are
useless.  I used the snap (arrows) to lock in on the frequency from both
(either) sides and kept the signal to the PC low enough that it locked
on the same frequency from both sides.  

Look at K6SE's "[Elecraft] Filter Alignment Using Spectrogram" message
and follow his advice.  He has calibrated many K2's whereas I have only
calibrated mine many times.  Haven't used his approach yet as I start at
the widest and work down, the same direction as you click through the
filters.  If the BFO has drifted during the process and you only adjust
one filter it will be for naught as the reference frequency stored will
be different than those stored for the other filters.  Thus you need to
change each filter, including the ones you didn't want to adjust, by one
click and back so that the frequency stored will all have the same
reference. 

Most important of all is that the reference clock must be right on or
you are wasting time.  

Rich 



-----Original Message-----
From: John McClain [mailto:digi2@earthlink.net] 
Sent: Thursday, June 06, 2002 1:26 PM
To: Rich Lentz; elecraft@mailman.qth.net
Subject: Re: [Elecraft] N0SS CW Filter Alignment 


Rich,
    I found your message very interesting but I didn't understand this
chart (i.e. what do the values of "ref -4 -6 -10" mean and where do
they come from)?  I am pleased with my filters but I must admit that
there is a change of 20 to 30 hz when I switch between USB and LSB
while using the same filter width (i.e USB with FL1 to LSB with FL1).
I also see a 20-30 hz change when I switch from CW FL1 (OPT1) and CW
FL2 (OPT1) but there is no shift between CW FL2 and CW FL3.  Even
though I have a registered copy of MixW, I have continued to use
Spectrogram because it has a resolution down to 2hz when you use the
cursor pointer and then read the pointed to frequency below the graph.
Try as I might, even though I don't feel that it is really necessary,
I can't get it any better than it currently is.

> On lower bands (below the reversal of BFO shift) got the following
> results reading the frequency off of the MIXW 2 display.  (Seems to
> provide a finer resolution than Spectrogram.)
>
>
> FL1 FL2 FL3 FL4
>
> USB   REF -4 -6 -10
> LSB REF 0.0 0.0 0.0
> CW REF -5 -5 -5
> CWR REF -7 -7 -7
>

    Was the above information obtained from MixW?

John
K7SVV
K2 #2569