QRN (noise) reduction?

Discussions about everything to do with SDRuno
KE2KB
Posts: 18
Joined: Fri Dec 02, 2016 1:11 am

QRN (noise) reduction?

Postby KE2KB » Sat Dec 03, 2016 5:40 pm

Hi;
I have a new SDRPlay running with SDRUno on Windows 10 and Windows 7 (dual-boot).
Everything is working, albeit I am still learning the more technical workings of SDRUno, but I have one complaint.
SDRUno doesn't seem to do enough to reduce the background noise (QRN) associated with simple random-wire antennas. I know that certain types of antenna are less noisy than others, but at this time, I have no choice but to use the random-wire with 9:1 un-un balun.

I enjoy working those realy weak signals way down in the mud, so good noise filtering is a must. I have had some luck playing with SDRUno's controls, ie; NB, IF gain, and audio, as well as my sound card (Realtek Hi-Def) eq settings. But all said and done, I could use a lot more noise filtering.
I'm thinking a 3rd party software app that hooks into SDRUno's output, and processes it as I like. I haven't yet looked into these apps, but will be shortly.
I was just wondering whether anyone has done any work in this area, and have any suggestions as to what might work best.

Thanks
Frank - KE2KB
Last edited by KE2KB on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
Reason: No reason

DXer
Posts: 1
Joined: Sun Dec 04, 2016 1:17 am

Re: QRN (noise) reduction?

Postby DXer » Sun Dec 04, 2016 1:47 am

All the usual stuff Frank.

-SDRplay unit placed 6 feet away from the PC
-ferrite beads placed at both ends of USB cable
-soft filter turned on in SDRuno >SDRuno RX control>EXW>AM soft filter, click box to turn on
-use soundcard EQ bands to lower sound hiss
-lower IF gain
-adjust bandwidth using red lines found in SDRplay AUX SP panel, note-hold down Ctrl button on keyboard to move
just one side of the red line bandwidth filter
-wait for better propagation
-use an outside (ground) on a balun style long wire antenna eg "EL-SWL" with a short under 35 feet (good) coax run- this antenna
style makes a huge difference on lowering the noise, forget using a piece of wire strung outside, way to much noise and low
signal performance with high impedance

PS if that all does not work take up golf
just kidding DXer
Last edited by DXer on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
Reason: No reason

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

Re: QRN (noise) reduction?

Postby KE2KB » Mon Dec 05, 2016 1:23 am

Thanks for the advice DXer;
I can't use the AM "Soft Filter", because I'm not listening to AM, but to SSB on the amateur bands.
My USB cable does have ferrites at each end, but perhaps I could buy a better one. I also tried a different USB port, but couldn't find one that was less noisy.
My "longwire" antenna does have a 9:1 un-un balun at the coax feed. That certainly works much better than the same antenna without the balun.
But you gave me an idea: If I could build a 40m dipole with a balun then I think it would outperform the wire I am using now, at least on 40m.
Problem is, I'm not sure I have the room for a 40m dipole. When I worked HF with the HW-101, I never had an antenna for 40m; only 15m and 20m, and both were dipoles with baluns.
I've lost one of the trees I could have used for that antenna, so I really don't know whether or not I can get a 40m dipole up there. I do have 50ft of LMR-400 cable still in its shrink-wrap, so that won't be an issue.

If I can't fit the 40m straight dipole, perhaps I can use an inverted V, also with the balun.
And if all else fails, I'll just take your last piece of advice, and wait for better band conditions!

Frank - KE2KB
Last edited by KE2KB on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
Reason: No reason

g,3vds
Posts: 12
Joined: Thu Nov 10, 2016 11:10 pm

Re: QRN (noise) reduction?

Postby g,3vds » Mon Dec 05, 2016 1:22 pm

Hello Frank

Noise is the modern plague for radio amateurs (I remember when it was TVI)
My adventures into SDR and the SDRplay have convinced me that they work well at coping with noise and outperform older equipment of similar price levels by a large margin.

I am using a Wellbrook magnetic loop as receive aerial which helps quite a lot. ( a bit expensive)

I am interested in constructing this when the wx gets warmer:-

http://www.crosscountrywireless.net/ter ... ted_u.html

You already have a balun. The resistor (NOT wirewound) can be bought off Amazon and 10m fibreglass fishing poles are quite cheap.

Enjoy
Roy
Last edited by g,3vds on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
Reason: No reason
G3VDS, NE5R

K0OD
Posts: 6
Joined: Sun Dec 04, 2016 5:00 pm

Re: QRN (noise) reduction?

Postby K0OD » Mon Dec 05, 2016 6:00 pm

Understand that normal atmospheric noise, if that's what you're referring to, *is* a signal. Directional antennas such as Yagis will reduce it from unwanted directions. Yes, I know most radios and antennas claim to be low noise. Nothing but marketing. Good radios pick up tons of atmospheric noise.

Is a resonant antenna quieter than a random wire or such? Nope, if you're talking about signal to noise ratio. In recent years I've been mostly using a 43' vertical which is only resonant NEAR 60 meters. Beverages are almost never resonant. BTW, was listening to the 160 meter CW contest over the weekend with my RSP1, and it was very impressive under those loud, crowded conditions.

K0OD (50+ years of DXing and contesting)
Last edited by K0OD on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
Reason: No reason

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

Re: QRN (noise) reduction?

Postby DanubeBCL » Mon Dec 05, 2016 7:05 pm

K0OD wrote:Understand that normal atmospheric noise, if that's what you're referring to, *is* a signal. Directional antennas such as Yagis will reduce it from unwanted directions. Yes, I know most radios and antennas claim to be low noise. Nothing but marketing. Good radios pick up tons of atmospheric noise.
Absolutely agreed.
And they pick up all the noise coming from modern comsumer electronics and RF polluting devices such as PLC/PLT modems in neighbouring houses. There are no "noisy" and "less noisy" antennas. The antennas just pick up what they get from your neighbourhood (or the atmosphere). The only chance of a directional antenna (as the EWE referred to in one of the postings) is that the lobe of the antenna points a bit away from the neighbouring houses which are producing RF noise. Nowadays the limiting factor for noise is not a good antenna, a good receiver or a good software. It is the noise level produced in the houses (mostly tolerated by the spectrum regulators and authorities due to lax laws about electromagnetic compliance).

73s, Heinrich (55 years of DX-ing)

Reason: No reason

13dka
Posts: 136
Joined: Sun Feb 14, 2016 8:40 am

Re: QRN (noise) reduction?

Postby 13dka » Mon Dec 05, 2016 10:05 pm

I think the OP was referring to AF noise reduction, but mixed that in with RF noise as well. Of course the main directive is to avoid noise in first place by means of antenna construction and location. But (not only) once you got the optimum out of your antenna, you may want to have some good DSP on the audio to make grass roots stations more intelligible and enjoyable to listen.

Unfortunately none of the available SDR softwares does a very good job at this. SDR# has some kind of adaptive noise reduction plug-in which is somewhat effective at removing noise but gives you that odd warbly wobbly phasey sound increasingly destroying intelligibility as well. SDR Console has 2 choices of this, and can use some simple (dynamic lowpass (I assume) algorithm built into Windows, that doesn't do remove much noise but doesn't do any harm either. Hard to tell what kind of animal the SDRuno noise reduction is, it feels similar to the one in HDSDR but more effective, but both fail at recovering weak and very noisy modulation for the most part.

I'm an advocate for digitally modeled analog (dynamic) filters instead of noise subtraction algorithms, because they usually sound much more natural. In the context of an SDR software the trick might be to find the right place to obtain the detector/sidechain signal for the filter. Also simply controlling the lowpass cutoff frequency may not be sufficient for all kinds of signals, and usually fails at very low SN ratios. Plenty of room for future developments! :)

Reason: No reason


Return to “SDRuno”

Who is online

Users browsing this forum: No registered users and 4 guests