RAN Technology

Beware of the LED Noisemaker!

Technical 0 Comments 01/02/2021 

MR-16 lamps have no home in the hamshack!

Posted By: Robert Nickels (ranickels)

Halogen type MR-16 lamps are commonly used in track lights and other spot lighting applications so what would be cooler than to drop in LED replacements!   

A lot, as it turns out.   The LED replacements are HORRIBLE RFI emitters that totally trashed several ham bands when I unknowingly installed them.

Halogen spot lights are 12 volt devices so it's long been common practice to supply switch mode power supplies with them rather than heavy transformers.   Fine, as far a it goes but those SMPS supplies are notorious RFI/EMI emitters and the once that came with my IKEA tracklights went in the garbage the first time I tried it.   Having things like 12 volt transformers on hand I just ran the lamps on 12 VAC and all was well - until the "upgrade to LED".

I have to say I thought it was great to be able to buy plug-in LED replacments at an affordable price.  I tried one and it worked from my AC supply and I liked the light so I bought a handful more.   All seemed well until I noticed a terribly strong blanket of broadband noise that completely wiped out the 75 meter band - only the strongest signals could be heard above the solid S9 noise level.  The SDR said it was at least 30-40 dB higher than normal.

The problem is the MR-16 replacement LEDs are designed to provide that convenient plug-in compatibility with existing 12 volt lighting systems.  That means that however many LEDs are needed internally - connected in series and parallel to get the desired output and color - they must run from a 12 volt source.  That means each MR-16 LED lamp has a little switch mode power supply inside!   And they put a high amount of RF on the 12 volt line which is then re-radiated by the wiring just like a little transmitter!    In fact, when multiple LEDs are used in the same lighting fixture their noise patterns combine and overlap to make the noise even worse.    On the bench I measured several volts of RF superimposed on the 12 volt DC supply wires, and no combination of filter capacitors or CLC filter networks would reduce it to any kind of tolerable level.  The noise was actually tunable with the supply voltage, varying from around 1.5 to 5 MHz as the supply varied from 8 to 15 volts.   Some combinations of filter capacitors actually increased the noise level as if a resonance was occurring!     It didn't take long to determine that the RF emissions from these LEDs would not be easily mitigated with typical measures and even so, the combined effect of multiple LEDs strung together with wires to re-radiated the conducted emissions was not predictable.

I purchased the FEIT brand and can't speak for other types, but they all probably use the same ICs and reference designs as the Maxim (below) so I'd expect the same results.    I could not find a readable part number on the 10-pin SMPS controller IC in the lamp I autopsied, but again the functionality is going to be the same - a current sensing buck converter.

The spectrum analyzer plot confirms these MR-16 LEDs have no place in the ham shack!   I have used LED "shop lights" which string lots of LEDs together and operate them directly from the AC main and since this type doesn't need to have the buck converter they are likely going to be much cleaner RFI-wise.


Click on the image title or on the image itself to open the full-sized image in a separate window.

    In 1958, the Multi Elmac Company was riding high on the ham radio waves.   The company had seen an opportunity to provide feature rich but affordable transmitters and receivers to hams itching to "go mobile", which was all the craze.   Instead of sticking a converter in front of the car radio like many competitors did, Elmac produced full-blown receivers that tu...  READ MORE
- Robert Nickels (ranickels),  09/28/2021 

Mystery Transmitter

where's the copper subchassis from?
Category: Vintage Ham Radio
 I didn't set out to buy this homebrew CW transmitter, it was included in an auction lot that I wanted so I had to take it to get the desired item.   But even though I always like to see good quality homebrew gear, this one is just a mystery.Most of the transmitter, including 6CL6 oscillator and buffer stages and a 6146 PA are built on a sub-chassis that is clearly part of a com...  READ MORE
- Robert Nickels (ranickels),  07/15/2021 

The Vector VR-50

last gasp from Swan/Atlas founder Herb Johnson
Category: Vintage Ham Radio
 Most hams are aware that Herb Johnson W6QKI founded Swan in Benson Arizona to make single-band SSB transceivers and then moved his operation to Oceanside CA where Swan thrived throughout the 1960s.   Swan merged with Cubic Corporation in 1967, and Johnson managed Swan as its subsidiary until 1973. Johnson founded Atlas Radio in 1974, with the assistance of Southcom International fo...  READ MORE
- Robert Nickels (ranickels),  07/12/2021 
   The Harvey-Wells Company was formed through a partnership between Clifford Harvey W1RF, and John Wells W1ZD in 1939.   Cliff Harvey had earlier founded Harvey Radio Labs in 1933, and prior to that, he was associated with the Hendricks and Harvey Company, another partnership. Producing police radios, transceivers, transmitters, and crystals. Their most popular product was the TBS-50 trans...  READ MORE
- Robert Nickels (ranickels),  06/18/2021 
    I became aware of a few hams playing with a thing designed to receive digital TV in Europe on your laptop - a little plug-in dongle that used an RTL-2832 IC and sold for $20 or so.    Some clever fellows had determined that it could be put into "radio mode" in which it would generate an IQ stream over USB, and by writing to control registers in the tuner IC, it could...  READ MORE
- Robert Nickels (ranickels),  06/13/2021 
    A while back I acquired a six channel HF transceiver made by the Radio Industries division of Hallicrafters, probably in the 1960s, called an SBT-20.    It is capable of 20 watts SSB or 5 watts AM (or CW with an optional board) in the range of 2-12 MHz and thus was probably aimed at commercial and light-duty military applications.   The radio could by ordered with fu...  READ MORE
- Robert Nickels (ranickels),  06/07/2021 
    I'm always thinking about interesting combinations of equipment to try out on the air.   One day while rearranging the shack I was getting ready to connect my Globe Scout Deluxe back up with a Collins 51S-1 receiver when the LED (the energy-efficient version of the old light bulb) came on.When I first started playing with DVB-T dongles back in 2012 I wanted an upconverter so I ...  READ MORE
- Robert Nickels (ranickels),  05/29/2021 

6AG7-6LG Novice Transmitter

Classic circuit with some modern twists
Category: Vintage Ham Radio
 There's a good chance that more homebrew ham transmitters have been built using a 6L6 than any other tube, and when combined with the superior performance of the 6AG7 oscillator, it's a hard combination to beat (click here for an explanation of the 6AG7's benefits)I'll be adding more info about this project soon, but one of my goals was to reproduce what was a budget-friendly...  READ MORE
- Robert Nickels (ranickels),  05/21/2021 
    All who operate AM in the midwest know and probably have talked to Masa, AB9MQ, who is a very active AM operator.    Having become interested in ham radio while still living in Japan in the early 1960s,  Masa's memories of the "dream rigs" is a bit differen than most US hams, and because the markets were still quite regional at the time, much of the ham gear...  READ MORE
- Robert Nickels (ranickels),  05/18/2021 

Hudson American Corporation

Manufacturer of marine radios in the 1940s
Category: Vintage Radio
 I enjoy playing with old marine radios that operated in the AM mode between 2-3 MHz.    This was the standard for "ship to shore" radio and telephone service from marine radio operators from after WWII until about 1970 when SSB was phased in and AM became obsolete.     Through this era a number of manufacturers were major players including RCA (Ra...  READ MORE
- Robert Nickels (ranickels),  05/02/2021 

VIEW News Item

Announcing the W9DYV Radio Society

honoring SSB pioneer Wes Schum W9DYV
VIEW News Item

Hamfests Return!

A quick look at the Wauseon OH swap on June 6, 2020
VIEW News Item

Making A Transistor Radio

in memory of Rev. George Dobbs G3RJV (SK)
VIEW News Item

Soviet Spy Radio found in forest

(oh yeah, I put that there...I'll take it now thanks!)
VIEW News Item

Take the Boatanchor Survey!

Let authors and organizers know what you're interested in
VIEW News Item

W9RAN's "VERSA-TR" (as featured in Dec. 2018 QST)

A Versatile T/R solution for SDRs and vintage radios
VIEW News Item


Cool mics from my collection and ones I wish were

(There are currently no Blogs.)