Question about knobs

[The Wizard]

I have a question about the knobs on the K3. I have my knobs on the Shift-Width position. When I just push the Width knob one time it says HI 3.50 next time I press the same knob again it says BW 4.00 on the display. I have the FC at *1.50. Why don’t both times I press the knob say the same thing? I think from monitoring my signal on Spectra Plus, that I am transmitting at about 4K but receiving at 3.50 or so. Are my assumptions correct? Or why can I not have both the BWs at 4K?


I can move the FC to 2.0 and transmit and receive at 4K, but when I try to record using my DVR, the bottom end of those I record shifts up and I lose the bottom 200 to 300 Hz. Not what I want to do on a faithful recording. Strange!!!! but probably cockpit problems by me.


Thanks for any help.


73 OZ






From:
 Larry Martus Wassmann
 Non omnis moriar
 (Not all of me will die) - - - The good I do will live forever.

www.w3oz.com
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[Don Wilhelm-4]

OZ,

The knob function changes from Width to Hi-Cut when you push it. Turning
the knob changes the receive passband width when in the WIDTH position
(look at the LED to determine the current state) or will change the
Audio High Frequency end of the bandpass when in the Hi-Cut position.

That knob and the one to its left Shift/Lo-Cut work in tandem.  When set
for Shift and Width, the SHIFT knob controls the center frequency and
the WIDTH knob controls the width.

When in LO-CUT/HI-CUT the left knob controls the lower frequency edge of
the passband and the right knob controls the high frequency edge of the
passband.  In this case, there is no use of the center frequency (it is
the midpoint of the low and high frequencies.

These knobs do not change the transmit bandpass, only receive.

You will likely find it easier to use the LO-CUT/HI-CUT on voice modes
and the SHIFT/WIDTH for CW.  For voice communications, you can only cut
a little from the low frequency end while maintaining intelligibility,
but you can cut the high end substantially to reduce QRM.  If you use
SHIFT/WIDTH in voice modes, you will find that you have to adjust the
center frequency with the SHIFT knob as you adjust the WIDTH to maintain
an intelligible response.

Using the LO/HI CUT knobs for voice may help you with your recordings
too because you can set the low and high ends as you choose.

73,
Don W3FPR

On 1/25/2014 12:23 PM, Larry Wassmann wrote:
> I have a question about the knobs on the K3. I have my knobs on the Shift-Width position. When I just push the Width knob one time it says HI 3.50 next time I press the same knob again it says BW 4.00 on the display. I have the FC at *1.50. Why don’t both times I press the knob say the same thing? I think from monitoring my signal on Spectra Plus, that I am transmitting at about 4K but receiving at 3.50 or so. Are my assumptions correct? Or why can I not have both the BWs at 4K?
>
>
> I can move the FC to 2.0 and transmit and receive at 4K, but when I try to record using my DVR, the bottom end of those I record shifts up and I lose the bottom 200 to 300 Hz. Not what I want to do on a faithful recording. Strange!!!! but probably cockpit problems by me.
>
>
>

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[Richard Ferch]

Larry,

If you look closely, what happens when you tap the Width knob is that it
changes from Shift-Width to Hi-Lo, and displays the high frequency limit
momentarily. When you tap it again, it changes back to Shift-Width, and
displays the width momentarily.

I think I've got this next part right: The upper and lower frequencies
are calculated from FC +/- BW/2. When the center frequency is set to 1.5
kHz and the bandwidth is 4.0 kHz, the calculated upper frequency is 3.5
kHz and the calculated lower frequency is -0.5 kHz (i.e. the other side
of zero beat). The K3's DSP imposes a low-frequency cutoff at 200 Hz, so
although the Lo frequency may read 0.0 (it won't go negative), the
actual lowest frequency that is passed is 0.2 kHz. Therefore, despite
your Width setting, the actual bandwidth you hear with this combination
is 3.3 kHz (3.5 - 0.2). What gets transmitted in turn may be different,
depending on which roofing filter is enabled as your transmit filter
(e.g. if it's a 2.7 kHz filter, that's an upper limit on the transmitted
bandpass regardless of what the DSP is set to).

If, on the other hand, you use the Hi/Lo Cut settings, you can set the
Lo to 0.2 (no point in going lower, because lower frequencies are not
passed through the DSP anyway), and then adjust the Hi to 4.2 (that's as
high as it will go - the DSP imposes an upper cutoff frequency of 4.2
kHz). If you check the FC and BW by tapping those controls, you will see
that they correspond to FC = 2.2 and BW = 4.0, exactly as the formulas
would predict (FC = (LO+HI)/2, BW = HI-LO).

73,
Rich VE3KI


W3OZ wrote:

> I have a question about the knobs on the K3. I have my knobs on the Shift-Width \
> position. When I just push the Width knob one time it says HI 3.50 next time I press \
> the same knob again it says BW 4.00 on the display. I have the FC at *1.50. Why \
> don’t both times I press the knob say the same thing? I think from monitoring my \
> signal on Spectra Plus, that I am transmitting at about 4K but receiving at 3.50 or \
> so. Are my assumptions correct? Or why can I not have both the BWs at 4K?
>
>
> I can move the FC to 2.0 and transmit and receive at 4K, but when I try to record \
> using my DVR, the bottom end of those I record shifts up and I lose the bottom 200 to \
> 300 Hz. Not what I want to do on a faithful recording. Strange!!!! but probably \
> cockpit problems by me.

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