SDRUno RSP1 NB doesn't do much

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KE2KB
Posts: 18
Joined: Fri Dec 02, 2016 1:11 am

SDRUno RSP1 NB doesn't do much

Postby KE2KB » Mon Dec 12, 2016 5:35 pm

Hi;
I'm running SDRUno 1.1 with SDRPlay RSP1.
I am listening on 20m amateur band, mode is USB.
Trying to pick out weak signals from the noise, I found that the NB (noise blanker) does very little to nothing. If I set threshold too low, then it cuts out the noise, and the signal, leaving a popping and crackling sound. If I set it too high, then it has no effect at all.
I have tried both Narrow and Wide filters with no satisfaction.
What I have found to be the mose effective method to pick out weak signals is to use the LNA and IF Gain (Gain reduction) in combination to find just the right settings.

Has anyone had any luck with the noise blanker?

Frank - KE2KB

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DanubeBCL
Posts: 180
Joined: Sat Jul 02, 2016 12:39 pm

Re: SDRUno RSP1 NB doesn't do much

Postby DanubeBCL » Mon Dec 12, 2016 5:49 pm

KE2KB wrote:Trying to pick out weak signals from the noise, I found that the NB (noise blanker) does very little to nothing.
Do not confuse noise blanker and (dynamic) noise reduction. Noise blankers are made for pulse shaped noise (like those ignition sparks of very old cars or electric pasture fences or similar). Try the noise reduction (NR). But do not expect wonders. When the baby is fallen in the well it is useless to throw a dry towel into the water. In other words: When the signal is already covered with high noise no reduction algorithm can bring a clean signal back. The best remedy against noise is a good antenna and a low noise environment. But the latter is hard to find in modern urban areas.
73s, Heinrich

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g1hbe
Posts: 238
Joined: Sat Jan 17, 2015 3:28 pm
Location: Cheshire

Re: SDRUno RSP1 NB doesn't do much

Postby g1hbe » Mon Dec 12, 2016 8:28 pm

I've found the noise blanker to be very effective against pulse-type and 'click' noise, which is what noise blankers are designed for. Noise Reduction is a different thing altogether, as Heinrich points out. A noise blanker will do nothing for 'hiss-type' or general interference, but a noise reducer will, as long as you adjust it correctly. Generally, digital noise reducers are best used sparingly or you end up with a horrible gurgling mess that has no noise but makes no sense!

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Andy

DanubeBCL
Posts: 180
Joined: Sat Jul 02, 2016 12:39 pm

Re: SDRUno RSP1 NB doesn't do much

Postby DanubeBCL » Tue Dec 13, 2016 10:11 am

g1hbe wrote:Generally, digital noise reducers are best used sparingly
That's correct. There are several people (I am one of them) who can read voice under strong hiss better when noise reduction is off. The NR takes away too much of the frequencies needed in our brain to discriminate the syllables. NRs are pretty impressive at first look when suddenly the hiss "goes away". But they also can cut off important parts of the audio spectrum needed for intelligibility.
73s, Heinrich

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PG3
Posts: 29
Joined: Mon Nov 14, 2016 6:04 am

Re: SDRUno RSP1 NB doesn't do much

Postby PG3 » Tue Dec 13, 2016 8:34 pm

I have found the NB to work best with the widest (8MHz) IF bandwidth. It's a trade off with noise as the noise gets better with higher decimation which of course reduces the IFBW. In some cases I've found a good trade-off compromise with a SR of 7 MHz and DEC of 4, only giving an IFBW of 1.5 MHz but this is often enough for the NB to have some affect.
Last edited by PG3 on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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NoelC
Posts: 76
Joined: Sun Nov 27, 2016 11:50 pm

Re: SDRUno RSP1 NB doesn't do much

Postby NoelC » Thu Jan 05, 2017 4:59 pm

Up until reading this thread I haven't found the NB feature useful at all, because I just didn't discover what kind of noise it would blank.

Now that I see that it's for impulse noise, I tried it again and wow, it gives impressive results! Consider the night and day difference between the waterfalls showing in this screen grab, taken just after enabling the Noise Blanker. The sound went from a loud cross between a 60Hz electrical short circuit and a dragster idling to a completely legible WWV signal against a modest hiss.

There are some frequencies around here that have a 60Hz zzzzt sound on them. I think it must come from those high voltage electrostatic air filters in A/C units (and in Florida here, the A/C is on almost all the time). Bug zappers for viruses and bacteria.

Image

Is there any reason the tooltip (popup) help for these controls can't give a clue what kinds of usage the features could be useful for? "Wide BW Noise Blanker" is simply too vague. No one would have to wonder what the NBW/NBN features would be useful for if the tooltip just said "Wide BW Noise Blanker - useful for smoothing impulse noise".

It's nice to have a forum, but even nicer to have the software help the user discover how to use it properly.

Now that I realize the NB feature can work so well, and have discovered that tweaking the NB level setting in the EX CONTROL window can really fine tune it, I do like it.

-Noel

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NoelC
Posts: 76
Joined: Sun Nov 27, 2016 11:50 pm

Re: SDRUno RSP1 NB doesn't do much

Postby NoelC » Fri Jan 13, 2017 5:15 pm

For what it's worth I just had a situation where the NB filter made a COMPLETELY unusable signal into something readable and actually quite clean.

I found Trenton Military Weather, USB on 15.034 MHz, completely unreadable because our washing machine has a computer control board that insists on broadcasting interference all across the band. Even though my antenna is outside and away from it, it completely destroys the HF band. It's not impulse noise, but shows up on the AUX SP as a band of interference about 1 kHz wide or a little more, and it repeats every 18 kHz or so.

Back before I got the SDRplay RSP1, for the longest time I just chose not to listen to my little SWL receiver whenever the washer was being run.

I saw this today in SDRuno and wondered, since it spread all across the band as a bunch of vertical lines, whether the Noise Blanking feature might take care of it. Wow, did it work well once I got the NB threshold in the EX CONTROL window set just right! Consider this screen grab. You can see in the MAIN SP waterfall where I enabled it. It made the signal not only readable, but quite pleasant to listen to. This is the kind of thing the S in SDR promised to bring to the party. It's great that it actually works so well.

Image

-Noel

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