Bob Miller wrote:
On Wed, 6 Aug 2008 22:38:20 -0400, "Hal Rosser"
wrote:

Interesting, but from past experience, the results may be just the opposite
a few months later because the source of the components may change over
time.
The components of fluorescent fixtures consists of
The ballast - which is usually outsourced by the fixture manufacturer.
Ballast types vary - GE, Universal, Advance, and several other Ballast
makers sell to fixture manufacturers.
The sockets - usually made by Leviton or Eagle or Rodale - but there are
others.
The lamp (the fluorescent lamp). Usually are not provided by the fixture
manufacturer. Made by Phillips, GE, Sylvania, etc.
Some even have a 'starter'.
--I expect the ballast is the critical component - some are magnetic, some
are electronic - its probably the culprit

I'm curious, what does the ballast do? I see it referred to on light
fixtures I've installed, but I've never quite figured out what it is.




All these bulb work by passing current through an ionized gas. The
forward voltage drop across the tube goes down as current goes up ( a
so-called negative resistance characteristic). If there weren't
something to limit the current, it would rise to the point of
destruction. You could use a resistor, but it's lossy. All you need is
some impedance, so an (almost lossless) inductor works fine. That is,
hook up an inductor with a reactance of 100 ohms to a 100Vac source, and
you'll get a current of 1 Amp, but no power is consumed because the
current is out of phase with the voltage.

You could also use a constant current regulator to do the same thing.
If the regulator is a variable duty cycle switcher, then the loss can be
quite low. That's what's in the electronic ballast... essentially a
constant current source.

In practice, there's some more aspects to getting a fluorescent lamp
started.. you have to ionize the gas inside, which you can do either
with a filament (gets things rolling, and once current is flowing, the
current in the gas keeps it ionized) or with a high voltage pulse (like
a flash tube).. (this is the difference between the "thermal starter"
where you see the tube glow reddish at the ends at the beginning, and
the "rapid start" types)

(This is also why fluorescent lamps are dimmer/harder to start in cold
temperatures..)



Where the term "ballast" came from, I don't know.

No No - when I mentioned changing places - I'm talking about the brands at
an arbitrary time in the future, should the same experiment be run at
another time in the future - using new fixtures at the time *(not the ones
you have now)* I would not expect the noisy one to fix itself, and I
wouldn't expect the quiet one to become noisy out of the blue.
sorry if I was unclear.

"News Features" wrote in message
...

"Hal Rosser" wrote in message
...
--I expect the ballast is the critical component - some are magnetic,
some are electronic - its probably the culprit

Hello, Hal.

I suspected the electronic ballast in the "bad" light myself. They both
use electronic ballasts. Perhaps it's an unfiltered ballast in the "bad"
light or something like that. They both are supposedly made in the USofA
so I can't blame it on the Chinese tendency to eliminate unnecessary items
like filter capacitors to save 18 cents of the cost.

I hope you're wrong about the two lights switching places; somehow, I
can't imagine the "bad" light gradually becoming RFI-quiet over time... by
what mechanism could that happen?

I am judging the lights as they are... one is noisy, the other is quiet.
It is somewhat amazing that we are trying to make excuses for this
situation rather than accept that some lights are noisy and some are
quiet! :^)

I'm curious, what does the ballast do? I see it referred to on light
fixtures I've installed, but I've never quite figured out what it is.

bob
k5qwg


The ballast serves two purposes -
it 'strikes the arc' (starts the current flow)
and it
Limits the current flow
(otherwise current would spike and destroy the fluorescent lamp)

The efficiency of a fluorescent fixture is dependent partly on the ballast -
and usually - electronic ballasts are the more efficient of the two. HPF
ballasts usually use less current than a standard ballast.
You Compare fixture efficiency by comparing the ballast specifications
assuming they use the same lamp.
The web site that John Smith posted a link to explains it pretty well.

"Jim Lux" wrote in message
...

snip

Where the term "ballast" came from, I don't know.

Possibly from the meaning "imparting stability." A ship's or boat's
ballast does that. Ballast around railroad ties does that. Ballast in a
hot air balloon does that.

A ballast tube in the filament circuit of a certain radio of my
acquaintance, the R-390A/URR, stabilizes the filament current for two
oscillator tubes, the VFO and the BFO.

News Features wrote:
...
They cost more, but they're worth every penny.

Regards,

Al W6LX

When the son was in his teens and our radio room was in the basement, we
had fluorescents lighting that basement ...

He built filters for the two, double-40w-tubes, units. If I remember
correctly, he use toroids out of old 8086-8088 IBM power supplies
with--I think, a 100pf, .1 uf and 1 uf caps at the end of the "hot" ac
lead right at the ballasts--to ground, and past the toroid coils. I do
know he made sure the cases of the ballasts were grounded well also ...

It most all the noise from the general shortwave receivers in the room
.... then we noticed the computers were generating a lot of noise ...
and, we never did clear that up to our liking.

Today, my laptop generates no noise if only a couple feet away from any
gear.

I do notice unacceptable noise from wifi switches/routers, and take
great care where I locate them and how I route their wiring.

Regards,
JS

On Aug 6, 2:01*am, "News Features"
wrote:
I'm not sure if this is the right newsgroup for this, but I wanted to get
this information out there to help others.

Our electrician arrived with brand new fluorescent under-counter lights to
install in our new kitchen. I told him, "Hey, I already bought lights at
Expo! Can you simply install mine?"

For some reason he was very reluctant to install my lights. He insisted that
his were just as good, if not better, than mine. I didn't have a strong
preference so I let him install his lights.

When it was finally dark, my wife turned them on to get the full effect. To
my horror, the AM radio two rooms away was instantly and completely
obliterated with RFI. I ran out to the shack and confirmed noise all the way
up to 20 meters.

The next day, I removed his lights and installed mine, and I was extremely
pleased to note not a hint of noise on any frequency, unless the receiver
was 6 inches from the light.

His lights: Bright Inch by Elite Lighting.

Mine: SlimLite by Hera Lighting.http://www.heralighting.com/hera/slimlite..html

They cost more, but they're worth every penny.

Regards,

Al *W6LX

I had a similar problem but it was with just one light out of several.
I returned it for a new one of the same brand. Could it have been that
only one of the new lights was causing the problem. I have also had a
couple of the compact flourescent light bulb replacements cause
problems. They become noisy but still function.


Jimmie

"JIMMIE" wrote in message
...

Could it have been that only one of the new lights was causing the
problem.

Jimmie

I verified that each of the lights by itself was a problem. Bad
manufacturing lot? Who knows? All I know is that they were unacceptably
RFI-polluting. I got rid of them and replaced them with lights that were--
right out of the box-- free of RFI. Problem solved. Hope this saves someone
else the three hours of work it cost me.

There is no way I was going to go back to the store and buy four more of the
bad lights on the basis of "Well, maybe four is too small of a sample size
to draw any conclusions." Fool me once, shame on you; fool me twice, shame
on me.

I reward companies that make RFI-friendly products and punish those that
don't. Always have lived by that dictum. I also try at every turn to educate
my neighbors to the same, so that we can all have as quiet an RF environment
as possible. Hence, my purpose in posting the original post here.

Al W6LX

News Features wrote:
"JIMMIE" wrote in message

...
I reward companies that make RFI-friendly products and punish those that
don't. Always have lived by that dictum. I also try at every turn to educate
my neighbors to the same, so that we can all have as quiet an RF environment
as possible. Hence, my purpose in posting the original post here.

Al W6LX

Absolutely, to everything in your post! The data is much appreciated
.... one thing I am still searching out is a transparent shield for the
tubes themselves; I have considered a shield made of screen but have
not acted on it (lazy/other-things-to-do.) I suspect rfi is using the
plasma discharge in the tube itself as some type of inefficient antenna,
as I have all shielded electronic ballasts ...

In addition, got any ideas he

What do you do about wifi switches/routers/wireless-nics/etc?

It seems, to me, the frequencies which the Ghz signal(s) are modulated
at, by the data stream of bits, is/are the real offender(s)? Other than
the strategic placement of these devices and directional antennas, I
have found little control over the RFI. I have found this to be a
problem on AM/FM/SW/VHF/SHF; I have noticed, some devices/brand-names
are less offensive than others ... I am, mostly all, Linksys with a
couple of NetGear nics ...

Any ideas from anyone would be appreciated here ... and yes, any
hard-cabling/power has been well choked with ferrite beads and filtered
power-strips ...

I am asking because I have noticed, a person working to cure one form of
RFI will, most likely, be working on "next one", next ... :-)

Regards,
JS

What do you do about wifi switches/routers/wireless-nics/etc?

It seems, to me, the frequencies which the Ghz signal(s) are modulated at,
by the data stream of bits, is/are the real offender(s)? Other than the
strategic placement of these devices and directional antennas, I have
found little control over the RFI.

Hi, John,

I have found the exact same thing as you. The modulation rate on those
wireless modems and such fall right in the HF band. You've already listed
what I've tried: antenna orientation.

However, most of those things have a variable power output. You can "log in"
to
them via a web interface; point your browser to their IP address and you can
perform administrative functions including adjusting the output power.

One of two things will happen: Increasing the output power may cause the
data rate between your computer and the router to increase, pushing the RFI
higher in the HF spectrum. Or, you may find that using the minimum power
possible you can reduce the interference level. I guess what I am saying is
try changing it and see what happens.

The one I am using right now is an AT&T wireless DSL modem made by 2Wire.

Good luck,

Al W6LX

Al Lorona wrote:

Hi, John,

I have found the exact same thing as you. The modulation rate on those
wireless modems and such fall right in the HF band. You've already listed
what I've tried: antenna orientation.

However, most of those things have a variable power output. You can "log in"
to
them via a web interface; point your browser to their IP address and you can
perform administrative functions including adjusting the output power.

One of two things will happen: Increasing the output power may cause the
data rate between your computer and the router to increase, pushing the RFI
higher in the HF spectrum. Or, you may find that using the minimum power
possible you can reduce the interference level. I guess what I am saying is
try changing it and see what happens.

The one I am using right now is an AT&T wireless DSL modem made by 2Wire.

Good luck,

Al W6LX

AL:

I was just "about" with a FSM and freq. meter ... the worst offender is
a Linksys "Wireless-N Home Router"--WRT150N ...

I am logging into 192.168.1.1 (the web interface to the router) to
search for the settings you mentioned, it has a TON of settings ... will
get back to you!

I cannot believe I didn't think of that, again, I claim Alzheimers'! ;-)

THANKS!

Regards,
JS AKA Brett :-)