I discovered that I've got one of the "bad" types of LV power supplies
for some of my lights, which, unfortunately, does a really nice job
of generating RFI over a very broad spectrum. (I don't think it
actually makes it as far as the 2m band, but it does show up on 50mHz
and lower.) Fortunately, the lights it powers aren't the primary
lighting for any of the rooms that they are in, so we try to keep them
turned off when I'm at the radio.
The power supply itself is in an easily accessible location in the
basement, and I wouldn't mind replacing it myself. Has anyone had any
experiences with non-noisy supplies like this that they'd recommend?
73,
David, K2DBK
On Fri, 26 Nov 2004 11:41:59 -0700, Bill VanAlstyne, W5WVO
<w5wvo@cybermesa.net> wrote:
> FWIW, my experience with switching LV power supplies of various kinds has been
> that the RFI they generate is common-mode. I've had no luck suppressing any
> noise from them with differential filters. That's just an anecdotal data
> point,
> nothing more -- not a theoretical opinion. :-)
>
> I've also had the experience with LV halogen lights that some of the switcher
> PSes clearly do not meet any standard for RFI, generating S9+ hash over the
> entire HF-VHF spectrum, while many others are completely clean. The difference
> is always huge -- they either do it or they don't. Makes me think that some
> manufacturers simply figure to get away with it and save big money on
> filtering
> components -- and apparently do so with relative impunity, since the devices
> are
> on the shelves and people buy them. After all, what percentage of typical
> consumers would even know or care about HF-VHF RFI from halogen PSes? Much
> less
> than 1%, probably much less than 0.1%, is my guess. The cost of refunding to
> their retailers for the occasional return is probably far less than the NRE
> and
> component costs of doing it right would have been.
>
> Bill / W5WVO
>
>
>
>
> Jim Lux wrote:
> > ----- Original Message -----
> > From: "Jim Brown" <jim@audiosystemsgroup.com>
> > To: <towertalk@contesting.com>
> > Sent: Thursday, November 25, 2004 12:16 PM
> > Subject: Re: [TowerTalk] Halogen Bulbs - 1.8 Mhz RFI
> >
> >
> >> On Thu, 25 Nov 2004 14:46:07 -0500, Floyd Sense wrote:
> >>
> >>> I doubt that there is much you can do to silence them.
> >>
> >> I agree that there are probably switching supplies causing the
> >> problem, but I wouldn't give up on fixing the problem without trying.
> >>
> >> There are three basic ways the RF can get out -- on the power line
> >> wiring, on the low voltage wiring to the lamps, and direct radiation
> >> from the power supply if it is unshielded. Direct radiation you
> >> probably can't fix except by replacing the supply. A standard, good
> >> power line filter should eliminate what is coming via the power
> >> line, and a multi-turn choke around a big ferrite, possibly in
> >> combination with a capacitive
> > filter
> >> should be able to kill what is on the low voltage wiring.
> >>
> >> You will need at least 8 turns around the typical big toroids to
> >> make an effective choke for 1.8 MHz. That choke should also work on
> >> 80 meters, but may be running out of effectiveness by 40 meters and
> >> above.
> >>
> >> 73,
> >>
> >> Jim Brown K9YC
> >>
> >>
> >
> > Depending on where the noise is coming from, a common mode filter
> > (i.e.running a bunch of turns of the twoconductor wire through a
> > ferrite)
> > might not help a lot. You might need a decent differential mode
> > choke/capacitor filter on the output of the low voltage supply. Put
> > the
> > choke first (so the capacitive load doesn't screw up the switching
> > regulator).
> >
> > Also, if you have a LV halogen scheme with the two "rails" from which
> > the
> > lamps hang, the rails can serve as a nice radiator of differential
> > mode
> > noise.
> >
> > By the way, if the halogen power supply is a low voltage device, it
> > would
> > need to comply with EN55011 (the EU equivalent of Part 15). Perhaps
> > the
> > problem is really that the halogen supply isn't working to spec?
> >
> >
> > _______________________________________________
> >
> > See: http://www.mscomputer.com for "Self Supporting Towers",
> > "Wireless Weather Stations", and lot's more. Call Toll Free,
> > 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
> >
> > _______________________________________________
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> > TowerTalk@contesting.com
> > http://lists.contesting.com/mailman/listinfo/towertalk
>
> _______________________________________________
>
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
> Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
> questions and ask for Sherman, W2FLA.
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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