Tracking down interference on 10 Meters

  • 1
  • Question
  • Updated 3 years ago
While tracking down a signal that was causing my WNB to go haywire on 10 Meters, I found this.....



Centered on 27.025 Mhz, this severely overdriven AM signal hails from Puerto Rico, and he was talking with someone equally wide - at least 90 Khz wide!  he had so many sharp impulse spikes that it was causing strange products to appear on 10 meters when the WNB was turned up.

I wish someone could shut these guys down.  BTW, it isn't the worst I have seen.  Last fall I saw a station on the same frequency that was fully 1.5 MHz wide!
Photo of Ken - NM9P

Ken - NM9P, Elmer

  • 3825 Posts
  • 1164 Reply Likes

Posted 3 years ago

  • 1
Photo of Ken - NM9P

Ken - NM9P, Elmer

  • 3825 Posts
  • 1164 Reply Likes
When he transmits, this is what happens on 10 meters when the WNB is turned on and turned to about 94.  If I turn it down to 85 or less, the display returns to normal, but other noise is not cancelled as well.

Photo of Walt - KZ1F

Walt - KZ1F

  • 3040 Posts
  • 640 Reply Likes
Isn't this the argument for a roofing filter? Honest question, not trying to provoke.
(Edited)
Photo of Tim - W4TME

Tim - W4TME, Customer Experience Manager

  • 8695 Posts
  • 3266 Reply Likes
Not on a direct sampling SDR.  What is probably needed is a narrow band NB.  We are looking into this option.
Photo of Dave - WB5NHL

Dave - WB5NHL

  • 264 Posts
  • 60 Reply Likes
Ken,  wait to you see what these guys do on SSB   I've seen some so bad that you have to look hard for the sideband suppression!
(Edited)
Photo of Al K0VM

Al K0VM, Elmer

  • 559 Posts
  • 93 Reply Likes
Ken,
  See what happens with the WNB on if you turn down the RF GAIN ( not AGC-T)..
AL, K0VM
Photo of Simon Lewis

Simon Lewis

  • 495 Posts
  • 117 Reply Likes
I'm seeing real odd ball things happening on 20m with WNB too ... strong VK's causing all sorts of odd effects with the WNB turned up anything beyond 80 or so. Then WNB seems to have no effect.

Is this hardware specific??

Lee W9OY's WNB showed no effects like this .. even at 100

I am running a 6500 and a 20m vertical - 1.5.0 on Win 10

I get a lot of strong VK signals after sunset and never had these issues before 1.5.0

no additional preamps .. gain is at 0 dB on the Flex

very unusual

I've tried playing with gains and AGC-T and not seeing an changes to WNB unless its level below 80

Thoughts?

Happy to investigate more ... 1.5.0 has some nice features but some not so nice side effects :(

73 Simon ZL4PLM
Photo of Tim - W4TME

Tim - W4TME, Customer Experience Manager

  • 8652 Posts
  • 3245 Reply Likes
Strong signals in the passband of the WNB will effect the blanking effectiveness because WNB is trying to determine what is correlated noise and what is actual signal and remove the noise.  When to add too much WNB aggressiveness and distortions happens, you have to turn down the WNB aggressiveness (threshold).   This is a simple case of "if it hurts, stop doing it".

The WNB threshold range scale has aggressiveness overhead dynamically built into it.  So this does not mean that if a setting of 70 works to blank your noise, changing it to a higher setting will necessarily be better.  It is like mic gain; you can over drive to distortion.
Photo of Ken - NM9P

Ken - NM9P, Elmer

  • 3825 Posts
  • 1164 Reply Likes
My suspicion is that the "operator's" severely overdriven signal was generating some really sharp spurs & spikes that confused the WNB because they were so wide.  When I turned the WNB down to about 85 things shaped up.  I have been fine tuning the AGC-T, RF gain (preamp) and WNB level on all bands since I installed it.  Most of the time it works pretty well.  But I can never run it all the way to 100.  Usually anything over 98 or 97 causes strange things to happen.  I am not surprised at this, because if they don't give us enough gain to make it fail, we will always gripe, thinking that it could go "just a little bit higher!"

My main purpose in the post was a lament that FCC can't seem to find these guys and shut them down.  Good grief, they tear up 2/3 or more of the legal band on 11 meters, and then bleed over into 10 Meters on us!

Ken - NM9P
Photo of pa0bie

pa0bie

  • 152 Posts
  • 20 Reply Likes
I have the same kind of things happening on my 6700.  Switching on the WNB with the slider above 90 , gives even an higher noise floor on the pan and waterfall. I have no strong stations in my neighborhood , only much noise from LED dimmers and that kind of things.
Photo of Tim - W4TME

Tim - W4TME, Customer Experience Manager

  • 8695 Posts
  • 3266 Reply Likes
See my comment above.  You have applied too much WNB aggressiveness (threshold) and you need to back it down to achieve optimal noise blanking..
Photo of Walt - KZ1F

Walt - KZ1F

  • 3040 Posts
  • 640 Reply Likes
Tim, in the context oh ham radio, would you define 'correlated noise',verse the uncorrelated kind?

The usage I haven't heard since Close Encounters of the Third Kind.

Thanks, Walt