What is the origin of the “pseudonoise” shown in the 2nd screenshot? Thanks, Mike, K6DRY

  • 1
  • Question
  • Updated 1 year ago
  • Answered
Photo of Michael Reid

Michael Reid

  • 10 Posts
  • 1 Reply Like

Posted 1 year ago

  • 1
Photo of Paul

Paul

  • 436 Posts
  • 128 Reply Likes
Hi Michael, impulses on the panadaptor and very broadband momentary bursts in the waterfall; looks like arcing of some sort. Could be on your property or further away. You could try systematically disconnecting circuits in your home to rule out a local source. Any old cars close by? This is reminiscent of ignition interferance - ie. deliberate arcing. Good luck tracing it.
Photo of Michael Reid

Michael Reid

  • 10 Posts
  • 1 Reply Like
Thanks, Paul...let me add some more information:  
1.  The two screenshots are 20 kHz different in width and are constant in appearance, the true noise level is -96.3 dBm and is constant, and the two screenshots can be reproduced by alternately changing the panadapter width from <= 220 kHz to >= 230 kHz.  There is no change in the audio signal heard or appearance of the waterfall.
2.  A similar "pseudonoise" occurs on 80 meters, with a different antenna, but not on the 20 --> 6 meter bands.
I summary, I cannot ascribe the "noise" to true noise, impulse or other.
Any further ideas?
Thanks, Mike, K6DRY
Photo of Tim - W4TME

Tim - W4TME, Customer Experience Manager

  • 9149 Posts
  • 3467 Reply Likes
Do you hear a relay click when you change the bandwidth of the panadapter?
Photo of George Molnar, KF2T

George Molnar, KF2T, Elmer

  • 1561 Posts
  • 552 Reply Likes
Does it change with the WNB setting?
Photo of Paul

Paul

  • 436 Posts
  • 128 Reply Likes
As you say, it's not stochastic which tends to imply some man-made source. It does have a vaguely periodic signature. If not a vehicle ignition, a poorly suppressed DC motor maybe?

Or if it happens in short bursts separated by relatively long intervals, it might be a fluorescent lamp being turned on or perhaps a poorly suppressed central heating (or immersion heater) thermostat.
(Edited)
Photo of lriehlou812 .

lriehlou812 .

  • 1 Post
  • 0 Reply Likes
Looks like my SDRPlay when I turn on my Panasonic Plasma TV.
Photo of Kevin K4VD, Elroy

Kevin K4VD, Elroy

  • 775 Posts
  • 171 Reply Likes
I think Tim is giving a clue to the answer. When I approach 230 KHz width of the panadapter I hear a relay click. I think that removes the pre-selector or makes some other "wide open" change? At any rate, I see a noisier display going from one side of the relay click to the other side and I think that's normal.

I think this is all normal and expected and sure someone will have a better explanation of why this occurs. I don't think this is showing you local noise or anything you need to troubleshoot or hunt down. All looks good at "normal" panadapter bandwidths and is only exposed after that relay click - at least in my case.

73,
Kev K4VD
Photo of Fred GLENN

Fred GLENN

  • 54 Posts
  • 7 Reply Likes
I can't tell from the screenshots if it appears in the waterfall or not. I spent many hours chasing down a similar "pseudo noise" that appeared in the main display but not on the waterfall. I eventually found this to be a display anomaly if you use the WEIGHTED AVERAGE setting when normal and low level noises are present. 
Photo of Fred GLENN

Fred GLENN

  • 54 Posts
  • 7 Reply Likes
I can't tell from the screenshots if it appears in the waterfall or not. I spent many hours chasing down a similar "pseudo noise" that appeared in the main display but not on the waterfall. I eventually found this to be a display anomaly if you use the WEIGHTED AVERAGE setting when normal and low level noises are present. 
Photo of Michael Reid

Michael Reid

  • 10 Posts
  • 1 Reply Like
Official Response
More info re my "pseudonoise" --

1.  Tim...no relay click at > < 220 kHz...but a "click" is heard at > < 440 kHz as the "WIDE" indicator of the increased bandwidth filter kicks in...however, see #4 below for solution to the pseudonoise...probably a deep glich in the SDR software.

2.  George...no change with WNB setting...

3.  Paul...no changes with all house lights / motors / plasma TV on versus off...

4.  Fred...THE SOLUTION!!!  "Waterfall Display" was set for "ON", and when switched to "OFF" all the pseudonoise disappeared, with no discernable change in the waterfall appearance...

Thank you to all!  A very peculiar finding indeed!   Mike, K6DRY
Photo of Ken - NM9P

Ken - NM9P, Elmer

  • 3975 Posts
  • 1227 Reply Likes
My experience has been that using weighted averaging emphasizes the peaks of sharply rising noise or signals. So it is actually showing noise that is present, but overemphasizes it.

It is handy in certain situations, I.e. Weak signals on Six Meters. But if you have a lot of sharply peaked, but random noise, it will display a lot of spikes that obscure other signals, and they may not be removed with WNB because they are not highly correlated noise.