A spectrum analyzer is great for this. Most have the sensitivity of a
receiver and any noise peaks (in or out of the ham bands) are almost
immediately identified Depending on the scope you can view from thr KHz
range to several GHz.
73
Roger (K8RI)
On 1/9/2015 7:48 PM, Tom Thompson wrote:
Hi Greg,
I suggest you build a fixture with a bulb socket on one end and an AC
plug on the other end so you can light the bulb. Before you put the
AC plug on the cord, wrap a toroid (eg FT117-43) full of #22 enamel
wire and terminate it in a BNC connector. Put the AC cord through the
toroid with 1 or 2 turns and then put on the AC plug. You now have an
RF current probe. Connect your radio (make sure not to transmit) with
a short piece of coax. Start with an incandescent bulb as a reference
and record the noise. The noise level should be negligible if the
toroid is not acting like an antenna. If it is, put it in an
enclosure. Next screw in your test bulbs and see what the noise is on
the various bands. If you have a calibrated receiver, the current
probe should be fairly flat over the HF band.
Hope this helps,
Tom W0IVJ
On 1/9/2015 12:22 PM, Greg Troxel wrote:
I have 2 LED bulbs (60W incandescent replacement) and have been unable
to hear them, which is good. Today I bought 3 more types (at the local
Ace, because I can return them if they make noise). So I'm about to
test them.
I am curious what people's experiences are in terms of which frequencies
are likely to be the problems. I would sort of expect 40 meters, just
because that seems to be the epicenter of RFI generally. But I realize
it's highly dependent on the switch-mode supplies in the bulbs. I also
saw a report of interference from LED bulbs meant to replace 60W metal
halide bulbs.
To do a quick test, my procedure is to put one of the new bulbs in a
basic desk lamp in the shack, turn off other known noise sources, use an
attic multiband dipole (one end of which is only 15' away), and step
through the bands 160m-6m and see if I can tell a difference turning the
light on and off. I will also check 145 MHz.
Does that make sense, or is there anything else that's easy that I can
do quickly? (I don't have a spectrum analyzer with a LISN....)
I'll post my notes on specific brands and findings.
73 de n1dam
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