Noise canceling /noise reducing / mud digging ?

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  • Updated 4 months ago
The recent thread about speaker leads me to an issue that I think is as important as speaker quality, devices to help dig out weak signals way down in the  natural noise floor or covered up by local electronic noise. RX EQ , good speakers, and SmartSDR NR capabilities notwithstanding, what outboard devices do you recommend for digging stuff out of the mud ?

Andy K3UK
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Andrew O'Brien

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Posted 3 years ago

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Lee, Elmer

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Try a W6LVP loop ant
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One Friday evening I contacted Larry W6LVP and asked a question about the kind of coax that he would recommend for his Magnetic Loop antenna. I was surprised to get a response with technical information within an hour or so. With this kind of customer service I decided to go ahead and order one of his antennas later that evening. I actually received the antenna on Monday afternoon within a couple days.

I have extreme electrical noise that was S-8 most of the time on my Carolina Windom and made my radio almost unusable. I temporarily installed the Magnetic Loop antenna on a short 5 FT pole in the backyard. With the XYL as the null monitor at the radio I called her on my cell phone and rotated the antenna by hand and was able to get a sharp noise null of about S-1. Very tight null when rotating just a few degrees one way or the other. Went in the house and couldn't believe the clear signals that were hidden by the previous high noise level. It reminded me of SWLing 50 years ago as a kid back in the good old days before the electrical noise environment turned so bad.

As I mentioned, the antenna arrived within a couple days and was of high quality construction and packed extremely well for shipment. I had read the previous reviews about Larry's product quality and customer service and my experience was also very good!!

I am planning to mount the antenna on a Channel Master rotator one of these days to get the full effect of the excellent directionally of this Magnetic Loop antenna. I even read where Broadcast Band Listeners use this antenna to pick up and select between multiple stations on the exact same AM frequencies.

I highly recommend Larry W6LVP and his Magnetic Loop antenna to other Hams and SWL listeners. He responds personally to emails within a business day usually just an hour or two. What more could a customer ask for?   Write a comment
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Michael Coslo

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QST had an article about home brewing a resonant speaker for CW, . Bad on anything else, but switchable. I'm going to build one because I need all the CW help I can get.
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Al / NN4ZZ

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Hi Andrew,
Thanks for the link, just added this to the APF enhancment idea also....

By the way if you build one of these speakers, you would have to add an amplifier also since the radio expects a powered speaker.  If FRS improves the APF feature you could just use your existing powered speakers.  

Regards, Al / NN4ZZ  
al (at) nn4zz (dot) com
SSDR / DAX / CAT/ 6700 -  V 1.10.16
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Ken - NM9P

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I built something similar years ago in high school, temporarily, by putting a small speaker over a glass tumbler. It happened to resonate by chance on the correct frequency. It was an experiment after my physic class had discussed audio resonance and wavelengths.

I like the tunable pvc pipe version.
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wouldn ́t it be possible to have two slices open at the same frequency and fed by two different aerials. and  hence forward a noise reducing program to filter out the QRN (M)?
a structure as used by noise reducing equipment as well.

73, PE3DON
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Ken - NM9P

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Possible with the 6700, but not 6300/6500 because they only have one SCU and can only use one antenna at a time.
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Tim - W4TME, Customer Experience Manager

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Noise canceling Bose over the ear headphones.
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Robbie - KI4TTZ

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That's what I use too.
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Rick Hadley - W0FG

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Me too. I only use my speakers for monitoring the band while I'm doing something else. Otherwise, the QC cans go on when I'm actually working someone.
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Gerald Capodieci

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The noise could be loud enough to overload the front end the down stream noise filtering would be no use. I'm in the big city.
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Is this a request for canceling receiver and environment noise or ambient noise? Bose NC headphones sure helps with a baby crying in the same room but doesn't do anything for noise levels at the receiver.

I'm not sure what could be done at the AF range to dig a signal out that is already below the noise level. Once it is covered by noise - meaning it is fully below the noise at the receiver - is there any algorithm or device that can possibly recreate the signal? You'd need something to work with. Otherwise we'd all be QRP and and have our DXCC Honor Roll.

If someone is screaming at me and a person right beside him is whispering at me there's no way I'm going to be able to pull the whisper out of the noise unless I punch the noisemaker in the nose before he can affect the whisperer.

I have found that I can see signals on the waterfall - weak but there - but I cannot seem to pick out the actual audio. I'm thinking this must be my lack of skill.

Kev K4VD
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Lee, Elmer

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The waterfall can "see" signals below the noise in your headphones.  The bandwidth of a pixel in the waterfall is something like 1.5hz.  Your only solution is to provide a signal at the antenna that improves the signal to noise

73  W9OY
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Thanks Lee, I will check into this. I've never  used any kind of preamplification outside the radio.
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Ken - NM9P

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Depending upon frequency and mode, a dedicated, low noise receiving antennas can be a great help.

Absent these, (and even with them) CW is probably the easiest mode to "tinker" with the SSDR controls.

Here is what I do to maximize CW reception.  In my situation....

CW tone to 500 Hz.  (you ear is more sensitive here than at higher frequencies.)

AGC in FAST Mode.  (better for fading signals, because a slower response will eat up a signal on fades.).

RX Filter at 50 Hz, Filter mode to Sharpest...

AGC-T initially adjusted to the "Knee"  (begin at the RH and move to the left until the background noise just begins to drop...This is probably the most important adjustment, and it interacts with all the other DSP functions.  So learn how to master this control!)

If they help, use WNB and/or NB, adjust to reduce noise, if effective, but not so high that they add splatter or baseline "jumping" with other strong signals.

RX EQ ON.... all sliders at bottom except 500 Hz all the way up.

APF ON set to 30-35

NR ON, set to 10-15.

As you add the final three, one at a time, you will obtain increasing levels of performance increase.

As you add each new level, you may need to tweak the AGC-T a bit.

I have one of the AUX buttons on my FlexControl Knob set to allow me to adjust AGC-T.  It is much easier than using the mouse.

Other ops will have different advice.  This is what works for me.

On 160, I have even had some success with the CW filter all the way to 25 Hz!

Ken - NM9P
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Ned K1NJ

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       An audio peak or peak/hold meter option might be handy for tuning CW or
calibration signals.  It should have linear response unlike an S-meter.  I used to
use one to compare filter responses in side-by-side receiver demos.

Ned,  K1NJ
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Chris Tate - N6WM, Elmer

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improved solar conditions ;-).
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Ken - NM9P

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LOL!  Amen!
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Brad A. Steffler

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West Mountain Radio Clear Speech DSP Noise Reduction Processor or  West Mountain Radio Clear Speech DSP Noise Reduction Speaker. I have heard rave reviews for them. I plan on getting one or the other myself.

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Manfred HB9FLU

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I use a Wellbrook loop and use it as auxiliary antenna on my MFJ-1026 noise canceling signal enhancer. This way all the noise doesn't enter the receiver. This is the way I go when noise is to strong for the superb noise canceling abilities of my 6300. The other positive effect is the possibility to enhance the signal strength of a weak station.

sorry my bad English and 73
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In addition to my W6LVP Magnetic Loop Antenna I have a Timewave ANC-4 Noise Reduction Device which takes care of local power line noise and other junk from plasma TVs etc. The key to make it effective is to be sure that you use a noise antenna that hears the same noise as the receive antenna does. Placement of the noise antenna is critical for best results. As I mentioned in my earlier post, with the W6LVP loop and the added ANC-4 it makes listening to Shortwave the way I remembered it growing up in the 50's and 60's before I became a ham. I like the way that I can pick up and pull out different Broadcast Band stations on the exact same frequency by changing the loop direction. I am using my ham radio which is a Yaesu FT-857 as my SWL receiver which is nice since it also has a good Noise Blanker and Digital Noise Reduction system built in. I have been stopping by in order to find figure out what some of the weird number, clandestine, and pirate stations are. Since getting my receive noise under control I have really been enjoying just relaxing and scanning the bands for exciting and entertaining stuff that is out there. The one thing I have not been able to do yet is pick up Long Wave broadcast stations in the 153-279Khz range. I live near St. Louis MO so maybe it will be impossible no matter what I do unless some unusual band conditions occur. I do hear a ton of aircraft beacons and stuff between 100-500Khz.
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Pat - WH6HI

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I use a BHI DSP FILTER in the receiver audio chain. Does a great job of reducing the background noise especially on SSB audio.