----- Original Message -----
From: "Bill VanAlstyne, W5WVO" <w5wvo@cybermesa.net>
To: <towertalk@contesting.com>
Sent: Friday, November 26, 2004 10:41 AM
Subject: Re: [TowerTalk] Halogen Bulbs - 1.8 Mhz RFI
> 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 agree that common mode is more likely, but, if the common mode doesn't fix
it, start looking at differential mode, especially if the LV wiring is such
that the wires aren't parallel and close (like the two rails a couple feet
apart scheme that you see).
>
> 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.
No question that this is the case. It's like cheap compact fluorescent
bulbs. They should last basically forever, but some kinds seem to die
fairly quickly (and even from "reputable brands" like GE). However, they're
well aware of the fact that you're not going to spend a lot of time to take
a $6 item back to the store, find the receipt, etc, just to get the warranty
replacement.
This is probably the biggest difference between products sold into the
consumer market (in qty 3 or 4) and products sold into the professional
builder's market (qty hundreds). An architect will quickly blacklist a
supplier that has problems, because replacing 500 fixtures is a real
expensive proposition. I suspect that the RFI potential for pro quality
stuff (stuff that's really pro quality, not just labeled as such, and
probably costing 3-4 times the consumer stuff) is much, much less.
I haven't tried it, but has anyone taken some hideously RFI generating
widget (that shouldn't) and tried to return it to a mass market retailer
(Wal-Mart, Home Depot)? I imagine they'd just take it, no questions asked
(it's not worth it to ask questions), but I wonder if there's any mechanism
to even follow up on it.
>
> 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
> >
>
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