[RFI] New Interference at kk0sd

[Don Kirk]

Hi Jim,

I just went back and looked at the audio on Garys recording using a real
benchtop oscilloscope instead of a software based audio scope.  I'm seeing
an obvious burst of noise at a rate of 60 Hz, and intermittently the bursts
disappear, sometimes for 1 or 2 cycles, sometimes 5 cycles, etc.  When I
originally looked at it using a software based audio scope I thought there
was sometimes bursts at a frequency of 120 Hz, but I'm not seeing that
using a benchtop oscilloscope connected right to the audio jack on my
laptop listening to Garys recording when he is not talking or changing
frequency (I even looked at both the Left and Right channel signal at the
same time to make sure I was not missing something).  It's possible that I
originally got tricked when using the software based scope when Gary was
constantly changing frequency or possibly talking and today I was careful
to avoid both those times on his recording.

A great example of where to grab the audio on his recording is starting at
the 1:16 mark or 1:37 mark just for a second.

I promised myself I was not going to post anymore today, but your recent
post made me dig my scope out :)

Just FYI, and 73,
Don (wd8dsb)

On Wed, Mar 24, 2021 at 2:26 PM Jim Brown <jim at audiosystemsgroup.com> wrote:

> There is a LOT of great advice in this post, but I'll zero in on this
> one, on the basis of my professional background in psychoacoustics (the
> science of how our brains process what we hear). There's a fundamental
> property of human hearing behind the success of what Ed describes. Human
> hearing is FAR more able to hear differences in the loudness of one
> sound compared to the other when they are more nearly equal. The two
> sounds here were the arcing sound and the broadband circuit noise.
>
> Also, we humans have very poor sensitivity to the loudness of a sound.
> It takes a change of 6-10 dB for us to perceive a sound as twice as loud
> (or half as loud), but a change of only 1-2 dB in the strength of a
> signal that is very close to the noise level can be the difference copy
> or no copy. And when I was recording mixing live sound for a jazz band,
> I rarely needed to move faders more than a dB or two once I had the mix
> "right" musically.
>
> 73, Jim K9YC
>
> On 3/23/2021 11:27 PM, Hare, Ed, W1RFI wrote:
> > I had a step attenuator, so I decided to try a trick. I drove to about
> where I thought it was strongest. I listended to the raucous buzz (120 Hz)
> and cranked in attentuation until the buzz dissapeared and all I heard was
> white noise from the receiver. I cranked back until I could JUST barely
> hear the buzz over the white noise of the receiver.  My ear was pretty good
> at that.  I again drove the line and heard it louder as I drove past a
>
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