[RFI] likely frequency for LED bulbs?

[Tom Thompson]

Also, my current probe sensitivity is 30 dB less that the actual power.  
That is to say if I put 0dBm into a 50 ohm resistor and sample one lead 
of the circuit, my current probe will show - 30 dBm.  So the spectral 
components reported at the -90 dBm level would actually represent -60 
dBm components due to the current probe.

Tom  W0IVJ

On 1/10/2015 2:24 PM, Tom Thompson wrote:
> I forgot to add that the measurements that I made where  I saw energy 
> were differential.
>
> Tom   W0IVJ
>
> On 1/10/2015 10:43 AM, Tom Thompson wrote:
>> I just made some light bulb measurements using an RF current probe, 
>> an oscilloscope, and a spectrum analyzer.  My current probe is flat 
>> within 3 dB from 500 kHz to over 50 MHz.  The common mode current on 
>> all bulbs was negligible through the entire HF band. The compact 
>> fluorescent and LED lamps had energy below 1 MHz but above 1 MHz the 
>> energy was down 70 dB.  The LED lamp had a switching speed of about 
>> 25 kHz.  There appeared to be no spectral components at the -90 dBm 
>> level between 1.8 and 30 MHz.  The bulbs used were a 200 watt 
>> incandescent, a GE 26 watt helical compact fluorescent made in China, 
>> and a FEIT 60 watt replacement LED that uses 9.5 watts made in Taiwan 
>> and available at COSTCO.  I can email the spectral plots to anyone 
>> interested.
>>
>> 73,   Tom   W0IVJ
>>
>> On 1/10/2015 5:52 AM, Greg Troxel wrote:
>>> wa4tuk <wa4tuk-rf at comcast.net> writes:
>>>
>>>> Thank you for posting your results. Information about what makes noise
>>>> and what is (relatively) quiet is hard to find. I will say I am
>>>> surprised. So far I have avoided LED lamps (A19 style) and use a mix
>>>> of incandescent and CFL where appropriate.
>>> I was surprised when I got the first one.
>>>
>>>> I would have thought the switching rate would have been in the 100kHz
>>>> range with harmonics radiating.
>>> Please note that I said I have other RFI sources; an attic antenna is
>>> not a good situation to start with.  I had dealt with a number of them,
>>> but the base level was higher than I expected yesterday.  So it's
>>> possible that these are problematic in quieter situations. Also, I
>>> didn't sweep everywhere, so if there is a square wave spectrum that's
>>> pretty limited to harmonics, I could well have missed it.
>>>
>>> Given that these cost only $5ish these days (and that you may want to
>>> preserve your stockpile of pre-ban bulbs :-) it seems worth buying one
>>> or two to try out to see if you can hear them.
>>>
>>> (Power supplies for LED strip lighting seem to be an entirely different
>>> situation.)
>>>
>>> 73 de n1dam
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>>>
>>
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