These tracks are fairly old and the aluminum outside shell of the track is
not bonded to the green. The plugs are only 2 prong. These hang from a
drop ceiling and just plug into outlets above the ceiling. The tracks are C
shaped with the opening down and wires on the sides in plastic insulator
strips, the fixtures stick into the opening and turn 90 degrees to lock in
and make contact with the wires.
David Robbins K1TTT
e-mail: mailto:k1ttt@arrl.net
web: http://wiki.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://k1ttt.net:7373
-----Original Message-----
From: RFI [mailto:rfi-bounces@contesting.com] On Behalf Of Jim Brown
Sent: Thursday, November 10, 2016 00:08
To: rfi@contesting.com
Subject: Re: [RFI] led bulb test
On Wed,11/9/2016 9:22 AM, David Robbins wrote:
> I ran some un-reproducible tests to see if it was acceptable for use
> near my station. my basic conclusion is that it is adequately quiet, I
> can not hear anything from it on my outside antennas. To try to find
> discrete signals or overall noise I ran a couple tests with an sdr
> connected to a test lead wrapped around the fixture and the bulb
> itself to find conducted signals or those radiated in the near field.
> First, the fundamental frequency of the switching supply is about
> 85khz with a rather wide noise band up to about 135khz. The wide
> noise band spreads out the energy of the harmonics over a fairly wide
> bandwidth so individual frequencies of harmonics can't be seen like a
> more stable source like monitors or computer clocks can. With my test
> lead loop around the fixture (an incandescent track light) I could see
> noise about 3db above the noise floor above about 25MHz, below that I
> saw no change in the noise floor and no discrete frequencies. I could
> not hear any increase in the noise floor with my 10m antennas aimed at the
shack from about 200' away or on 15m from about 100' away.
Thanks for posting this work. Several comments. First, the use of an SDR to
look at spectra of the noise is a really good idea. I'm currently working on
updates to the ARRL Handbook, and this is something I'm suggesting. The
SDRPlay ($130) is a particularly good choice, because it has a very wide
tuning range and can display a large chunk of spectrum at one time.
Second, while this lamp is acceptable for your station with antennas spaced
100-200 ft from the fixture, it might not be for hams with antennas much
closer to these lamps. Repeating your tests with closer spacing would be
useful. So would the SDR looking at the spectrum at the antenna.
Third, it would be interesting to explore the effect of the lighting track
on radiated noise, if any. The tracks I've seen are parallel wires in a
metallic tray that is open on one side, and the tray should be bonded to the
green wire. Was that true for the track in which you tested? The SMPS is, of
course, inside the base of the bulb, with connection only to phase and
neutral.
Another great alternative for shack lighting are strips of LEDs sold by
vendors at ham flea markets. Many of them self-regulate to a wide range of
DC and AC voltages.Wired Communications is a good vendor who exhibits at
Pacificon and Visalia, and has an online presence. But don't use their SMPS
to run the lights -- use your own linear wall wart. I'm lighting my shack
with five strips that draw a combined 1.25A from my 12V system.
73, Jim K9YC
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