[Elecraft] LED Lamps and HF RFI?

[David Gilbert]

LEDs are low voltage DC current driven devices, and those in the K3 are 
easily driven from the internal supplies.  LED bulbs used in residential 
lighting each have a power supply in their base that has to efficiently 
drop the 120 VAC source down to low voltage DC current, and that pretty 
much requires some sort of chopped waveform.  The potential of RF hash 
is certainly there, and I've heard reports of such behavior in early 
versions of the product, but I have roughly 40 LED bulbs of various 
sorts (all Utilitech store brand from Lowes) and I've been able to 
discern any additional background noise on my K3 as a result.  I have 
three of them overhead in my shack and turning them on/off yields no 
noticeable change on any band.

That being said, I don't think there is any hard and fast rule for what 
you will get from any particular brand.  I've never seen any relevant 
specs on any LED bulbs and I doubt there ever will be.  If I was really 
worried about it and unwilling to simply try one, I'd suggest going with 
a European brand like Siemens or Philips/Sylvania/Osram simply because 
Europe seems to be more sensitive to such issues compared with the U.S. 
or Asia.  In my opinion, though, the best plan would be to buy bulbs 
from someplace with a friendly return policy (which is why I bought them 
from Lowes) and take them back if they caused problems.

Dave   AB7E




On 5/11/2015 7:13 PM, Dauer, Edward wrote:
> Had an electrician at the operating QTH today to discuss replacing the
> recessed ³can² lighting throughout the house.  He suggested replacing the
> incandescent cans (now 65 watts per bulb) with LED lamps (same lumens with
> 10-13 watts per bulb).  I have looked at the Internet on the question of
> RFI from LED bulbs and see wildly inconsistent reports.  It is the case
> that HF radios like the K3 have LEDs in their panels; but I would be
> installing as many as 60 LED fixtures running at 10-13 watts each.  My
> caution comes from my novice days in the 50s when a single fluorescent
> lamp put my hamming out of business - things were quiet when the only
> light source was the filament of a 6146 and the dial lamps on the HQ-100.
> I know that LEDs aren¹t at all the same; but I don¹t want to relamp the
> house if it puts me off the air.  And if they (or their power supplies) do
> generate RFI in the HF bands, would the K3¹s NR get rid of it?  Anyone
> have any good data on this?
>
> Tnx,
>
> Ted, KN1CBR
>
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