filter and dsp operation possible problem

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  • Problem
  • Updated 5 years ago
  • Not a Problem
Good Morning.
Flex 6700 GPSDO version 0.12.17 using Win 7.
Question: Should the filters and dsp setting be independantly controlled/set for each panadapter/slice receiver? I am assumming that they are. For example a 50 hertz filter on slice 1 mode CW and a 4kHz filter, SSB mode on slice 2 (second panadapter).
However looking at the 2 output audio streams on a spectrum analyzer shows that you can not set a narrow filter on just one slice. If you want a 50 hertz filter on the CW slice you have to set the other slice to CW and 50 hertz also, or else you can only get whatever filter width that the higher slice is set to. 4 kHz in the case above. If you have three panadapters and three slice receivers all have to be set to the same filter bandwidth (BW) you want, or else they are set to the highest slice BW. There does seem to be some slight change in the spectrums when you select a narrower BW on one slice but only as if you were removing 50 Hertz from the high end of the highest filter.
This is repeatable and very easy to see looking at the audio spectrums. It also holds true for any desired Filter BW (100,400,1k, 4k, etc.).
This is also true with the AM filters.
The filter BW shown on the cursor changes as they should as you step through the filters.
Following up on this problem, I checked the operation of the DSP NR (noise reduction) button and found that both slices have to be set to the same thing (i.e. NB on) to get the full noise reduction available. If 3 panadapter and slices are used all three NR buttons have to be selected to get the full noise reduction. If you only select one slice NR button you get what looks like 1/3 reduction, select another slice NR button the spectrum drops another 1/3 to 2/3. Select the final slice NR button and you finally get the full reduction on the audio spectrum. These tests are also repeatable.
These assumed problems are also audible in the speaker/headphones once you realize there may be a problem.
Of course these "problems" may not be a problem if my assumption of indepentant filters is wrong and they are designed to work differently than I think.
I hope I have explained this well enough.
BTU Al N4AB
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Al

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Posted 5 years ago

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Tim - W4TME, Customer Experience Manager

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Al,

Panadapters are only filtered using the various low pass, high pass and band pass (preselector) filters. How and whn these filter are enabled depend of the center frequency and frequency spread of the panadapter. If you see the WIDE indicator in the top right hand side of the Panadapter, that indicates that the band pass preselectors are no longer enabled.

Slice Receivers have their own independnet RX passband filtering.

We have not had any reports of the behavior you describe in you problem topic.

Note that the sharpness of the CW filters has not been optimized, so a 50 Hz filter has a wide skirt and this is what you may be hearing. My testing indicates that the slice filters are independent.

If you believe otherwise, we are interested in a detailed description of you test setup and testing procedure. We would also like to see the spectrum responses for the behavior where changing the filter slice on one slice effect the filter response on another slice.
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Eric - KE5DTO, Official Rep

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Al,

It sounds like there may be confusion about how multiple slices are processed and presented as audio to your ears. When multiple slices are open (and not muted), they are mixed and presented as a single audio stream using the gain and pan settings that are specific to each slice.

Let's take an example: Let's say that you have 2 slices open -- one in CW mode narrowed down to 100Hz and one in USB mode running 2.7kHz. With the default Pan settings for these slices, you are still going to hear 2.7kHz of audio in both ears (corresponding to the 2.7kHz USB slice).

You can verify that this is what is going on by panning the CW to the left ear and the USB slice to the right ear (click the speaker icon on the Slice info panel and drag the Pan control toward the L or R). You will notice that the CW signal has less noise (since it is just 100Hz) while the right ear has the full 2.7kHz bandwidth of the USB slice.

Similarly, enabling the NB (Noise Blanker) or other DSP options on a single slice applies that processing only to that slice.

Does this help?
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Al

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Eric and Tim, I completly missed the Left/Right slider in my mind when I was trying to figure out why the filters and dsp didn't work the way I thought they should. Talk about a light bulb going off in your head. I keep on thinking 2 panadapter slices,and 2 audio slices equals 2 independant channels, duh. Thanks for setting me strait and not starting the reply with "you idiot".
73, Al N4AB
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Tim - W4TME, Customer Experience Manager

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Don't fret over it. It takes a while to understand new paradigms. It still happens to me daily.

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