[Elecraft] Noise from LEDs

[Matthew Cook]

John,

That tells you that the noise from the LED power supply is differential
noise and not common mode.  You might find this URL helpful, just focus on
the pictures on the first page.

http://www.murata.com/~/media/webrenewal/products/emc/emifil/knowhow/26to30.ashx

Figuring out what type of noise you're dealing with is the first step to
reducing it.   You might find it easier to replace the LED driver you're
using with another unit and see if you get an improvement.

73

Matthew
VK5ZM

On 2 February 2016 at 14:18, johnpierce <ja-pierce at verizon.net> wrote:

> My kitchen, under cabinet lights, are LEDs.  With those lights turned on my
> noise floor changes from -128db to -102db.  If the circuit is changed to a
> different phase the noise improves by 6db.  All of this at 7mhz and other
> higher bands.  Needless to say the AM broadcast band is highly affected by
> the LEDs.
>
>
>
> Placing a type 31 core with three turn of the AC line feeding the LED power
> supply and a clamp on 31 core on the LED side of the power supply provides
> no improvement!  I do not have an oscilloscope to look at the waveforms.
> But given what I have done, why is there no improvement?  I was following
> recommendations provided by NK7Z.
>
>
>
> AD2F,  John
>
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