Notch Filter Question

Robert11
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Joined: Fri Aug 21, 2020 8:49 pm

Notch Filter Question

#1

Unread post by Robert11 »

Hello,

I imagine the screen to do it is "somewhere," but can't seem to find it.

Is it possible to create a Notch filter to notch out, e.g., a (selected) small am spread of frequencies with the program ?
Where, and/or how, please ?

(I know of the MW/FM Notch button in the ribbon, but would like to be able to select what free's I want notched out)

And,

I see in the Receive DSP the option the option: Notch OFF / Auto Enable box.
And if selected, the Level Slider.

Could someone please explain this a bit for me re what it does ?
What is it actually Notching, etc. ?

Thanks,
Bob

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G0OFE
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Re: Notch Filter Question

#2

Unread post by G0OFE »

It's an audio notch - eliminates carriers within the demodulated area automatically in SSB mode. The level slider controls how strong it notches.

There is not currently any other notch function in Console.
Jim, Bournemouth IO90BR
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Robert111
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From OP: Re: Notch Filter Question

#3

Unread post by Robert111 »

Hi Jim,

Thanks for reply.

Seems like it might be a worthwhile item to add to Simon's "Wish List"

Regards, and stay well,
Bob

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G0OFE
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Re: Notch Filter Question

#4

Unread post by G0OFE »

Indeed.. it has been suggested before by myself to block spot freqs before demodulation (to try and remove narrow but strong local carriers killing weak broadcast FM signals on Band 2) but it's not a simple matter. There may be a solution, but Simon has a lot of other priorities, understandably this is not high on the list at this time.

I have moved this post to the "Requests" sub-board, as it is more appropriate there.
Jim, Bournemouth IO90BR
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steamfire
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Re: Notch Filter Question

#5

Unread post by steamfire »

How would I null out birdies if there's no user adjustable notch filter?

I am trying to decode an AFSK signal 50khz wide, but it is straddling two birdies/DC offsets from a HackRF. The birdies are stronger than the AFSK tones most of the time, and are present when the transmitter is not turned on, so it's not a signal carrier from my data transmitter. I'd like to notch those two frequencies down.

If this is not possible, how do I export the IF recording compatible with other SDR apps that have notch filters?

Thanks,
Dan
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Birdies without the actual signal
Birdies without the actual signal
Signal overlaid on birdies
Signal overlaid on birdies

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Simon G4ELI
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Re: Notch Filter Question

#6

Unread post by Simon G4ELI »

I'm afraid there's nothing you can do until I add a manual notch / notches.
Simon Brown :shock:
www.sdr-radio.com

Do not send me direct e-mail, thank-you!

sm7yes
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Re: Notch Filter Question

#7

Unread post by sm7yes »

Simon G4ELI wrote: Mon Sep 14, 2020 6:13 am I'm afraid there's nothing you can do until I add a manual notch / notches.
Please do so. I really like sdr console but also love the notch filter in sdr#. If you can do something similar with adjustable noth bandwidth with almost square notchfilter response like if-bandpassmfilters but inverted, and easily added in the receive pane window with a click and adjustable reject-band like you do with if-bandpass filters by dragging at the edge. Clicking inside the same turs off again, and you can add multiple notches just by clicking on different positions in the receive pane window.

I am often using notch both on BC FM and on HF and hence that i must SDR# during those situations. Ideal would be of course SDR console with same function so i can use it with my ELAD FDM S3 which i recently acquired. If this happens I will instantly make a good donation via paypal.

You might think it is not useful on BC FM but in fact you can improve receptions by removing an interfering sideband carrier from radio data modulation on an adjacent stronger FM-station. You can remove just 500 Hz of spectrum inside the 150 kHz FM BC spectrum and therefore you can keep the wider bandwidth instead for reducing the overall bandwidth to get rid of the carrier.

Another example is when listening on Chaine 252 kHz LW there are 3 weak carriers around inside the modulation spectrum both sidebands and each tone rejected with 50 Hz notches on RF and the reception quality gets perfect and still wide 14 kHz bandwidth to enjoy the listening with good fidelity! I really miss this on SDR Console.

Please try the IF-notch in SDR# and do something similar. This is the best notchfilter by all SDR programs available. I promise! Only similar is found in Theteis SDR software for Apache Labs ANAN-transceivers. In SDR# you open the built in "IF Multi-Notch"-plug and tick the square "IF Spectrum" to open IF-spectrum window, and then you kan play around inside this window with both if bandpass filter and the notches just by clicking and dragging. ITS WONDERFUL!

73s
Per
ELAD FDM-S3 with DCM and DL2EBV-6 bandpass
Elad FDM-S2
Winradio Excalibur G31DDC with Microtelecom FM+
Airspy HF+ dual port
Airspy HF+ Discovery
RSP1 clone, 5 ports
Apache Labs ANAN-100D
Sony XDR-F1HD Konrad mod
JRC NRD-535D
Kenwood TS-950SDX

sm7yes
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Re: Notch Filter Question

#8

Unread post by sm7yes »

Examples on nice notches:

ELAD FDM-S3 with DCM and DL2EBV-6 bandpass
Elad FDM-S2
Winradio Excalibur G31DDC with Microtelecom FM+
Airspy HF+ dual port
Airspy HF+ Discovery
RSP1 clone, 5 ports
Apache Labs ANAN-100D
Sony XDR-F1HD Konrad mod
JRC NRD-535D
Kenwood TS-950SDX

sm7yes
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Re: Notch Filter Question

#9

Unread post by sm7yes »

Here another example:
ELAD FDM-S3 with DCM and DL2EBV-6 bandpass
Elad FDM-S2
Winradio Excalibur G31DDC with Microtelecom FM+
Airspy HF+ dual port
Airspy HF+ Discovery
RSP1 clone, 5 ports
Apache Labs ANAN-100D
Sony XDR-F1HD Konrad mod
JRC NRD-535D
Kenwood TS-950SDX

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