Notch function

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Notch function

Postby WA2DVU » Mon Nov 27, 2017 1:12 pm

Where is the notch function located? 73, Bill, WA2DVU
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Re: Notch function

Postby jeffreydoran » Mon Nov 27, 2017 1:33 pm

Bill, in the the noise blanker button section. You will see ANF (Automatic) and MNF (Manual). 2 clicks of the NR button activates NR2 which is especially effective at reducing background noise. The notch filters work as expected.

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Re: Notch function

Postby w-u-2-o » Mon Nov 27, 2017 2:38 pm

This is from the 3.3.6 release notes, where the MNF function first appeared:

"This particular tool, Multi Notch Filter (MNF), allows you to specify up to 1024 notches. The notches are specified by RF frequency and width and will be invoked, as needed, when they overlap the passband. This feature is useful for those who have interference that consistently appears on specific frequencies.

To avoid phase distortion, the notches are implemented with linear phase. Also, they introduce no additional processing delay nor do they consume any additional CPU cycles once you're on frequency and the notches are set up. This is all accomplished by simply "cutting" the notches into the existing bandpass filters rather than adding additional filters.

Sorry, there's currently no fancy on-panadapter UI for this. If you have programming talents and would like to write one, please let us know.

To enter notches, in Setup, go to the new DSP / MNF tab. To Add a notch, click Add then enter the Center Frequency and Notch Width and click Enter. Once multiple notches are in the database, you can scroll back and forth through them using the up/down arrows on the "Notch #" control. When you add a new notch, it will be added immediately after the notch being viewed. You can Edit notches by clicking Edit, making your changes, then clicking Enter. You can Delete a notch by scrolling to the notch and clicking Delete. If you were to enter very narrow notch widths (less than 200Hz with default filter settings), you might not achieve the full attenuation of >100dB. By leaving "Auto-Increase width" checked, if your specified width is not enough to achieve >100dB notch depth, it will be automatically increased for you when the filter is cut in the passband. When you are entering a new notch, rather than typing in the Center Frequency, you also have the option to tune VFO-A to the desired frequency and then click the VFOA button."

These MNFs act only on the final RX passband. You can't tell where they are from the panadapter display, they don't effect the display on the pandapter or waterfall. You can only see where they are at and what they are doing by using the Spectrum display. Because of the lack of a good, graphical user interface for them, I find them quite difficult to use to defeat random, real-time interferers. As the release notes imply, because of this, they are more useful for notching consistent and predictable interferers.

I find NR2 and ANF, both separately and together, generally more effective for most interference situations, but not always.


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Re: Notch function

Postby Walter » Mon Nov 27, 2017 11:12 pm

:D Bill just grab the filter with the mouse(left click and hold)then go right or left.73

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