K2 Filter Setup CW vs CW Reverse

[Ben Hofmann K1NT]

I've been playing around with the filter setup in my
K2 S/N 4429 to get them to my liking.

Has anyone had any luck getting the difference in
pitch between CW and CW reverse to a reasonable level.
 I'd really like it to be within 10Hz if possible.
>From my understanding the factor which determines this
is the accuracy which the original signal has been
tuned in.  I am confident in my ability to zero beat a
received signal against the spot tone, which should
make the tones of the two within 5Hz of each
other(based on the 10Hz resolution of the VFO).  But
even when a signal is zero beat it seems my tone pitch
between CW and CW reverse in the filters is closer to
30Hz.

I've noticed that there is some discrepancy in the
requested sidetone pitch in the menu setting and the
actual spot tone frequency.  I'm not sure if this has
anything to do with it or not.  I get an actual 600Hz
tone when the sidetone is set for 590Hz.  Measurements
made with Spectrogram.

Anyone have any insight, or is this small of a pitch
difference between CW and CW reverse not possible due
to DAC resolution maybe?

-Ben  KB1AHR
K2 S/N 4429
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Ron D'Eau Claire-2]

Ben KB1AHR wrote:

Has anyone had any luck getting the difference in
pitch between CW and CW reverse to a reasonable level.
 I'd really like it to be within 10Hz if possible.
>From my understanding the factor which determines this
is the accuracy which the original signal has been
tuned in.  I am confident in my ability to zero beat a
received signal against the spot tone, which should
make the tones of the two within 5Hz of each
other(based on the 10Hz resolution of the VFO).  But
even when a signal is zero beat it seems my tone pitch
between CW and CW reverse in the filters is closer to
30Hz.

I've noticed that there is some discrepancy in the
requested sidetone pitch in the menu setting and the
actual spot tone frequency.  I'm not sure if this has
anything to do with it or not.  I get an actual 600Hz
tone when the sidetone is set for 590Hz.  Measurements
made with Spectrogram.

Anyone have any insight, or is this small of a pitch
difference between CW and CW reverse not possible due
to DAC resolution maybe?

Reply: -----------------------------------

Yes, it's a DAC resolution issue if you've set the filters up properly in
the first place. The shift in tone between CWn and CWr should be no greater
than it is between any two filter settings. The only thing that's changing
is the BFO frequency in each case. The DAC resolution may allow as much as
20 or 30 Hz variation, but it should never be more than that and can usually
be set to be less.

It has nothing to do with your tuning "accuracy" in operation.

Indeed, you'll be 'chasing your tail' if you try to tweak the settings by
listening to a tone produced by a received signal! The BFO and local
oscillator (so-called PLL oscillator in the K2) interact under firmware
control to ensure you don't change the beat note, but only change the
apparent position of the filter passband in relation to the signal!

A difference between the actual and measured sidetone frequency using
Spectrogram depends upon the accuracy of the sound card clock in your
computer! Your computer sound card should be "fairly close" but it is not a
precision instrument that you can rely on for detailed measurements of the
absolute frequency. Indeed, if you've set your 4 MHz clock in the K2
accurately, I'd be more inclined to believe the K2 over the typical sound
card oscillator.

Ron AC7AC


_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com