Hi,

Do receiving only (30 MHz on down) and presently just have a random length
wire running around attic.
Will be putting up an outside antenna once things warm up a bit.

Was wondering about household type of noise sources.

Not sure if the noise I'm picking up now is mainly from household sources
or atmospheric.
Other than turning stuff on and off, any easy way way to tell ?

Anyway, regarding household noise (other than on-off type of transients):

I imagine that the 60 Hz power stuff isn't much of a problem seeing where
most of the
listening is done.
Is this generally true, or are the higher order harmonics a problem ?

So, where is most of the noise coming from:
Is it Mainly from:

PC's
broadband cable modems
small 120 to 12 V type of wal-warts
Or,... ?

Any filters or other approaches to minimize ?

Trying to get a good understanding on this: How quickly do the fields from
these sources diminish with distance
(I would imagine very quickly, but am not sure) ?

Thanks,
Bob

If you can operate your receiver off battery power, I suggest shutting
off all the power at your circuit breaker. Then turn your receiver on
and see how much 'quieter' things are. That should show you how much of
the noise you hear is atmospheric and how much of it is from sources
inside the house.

If you want to minimize the noise coming from various appliances in
your home, pick up some ferrite beads and attach them to all the power
cords. I did this and it helps. I also keep my receivers as far away
from other appliances, especially computers, printers, etc., as
possible. Yes, this might mean that you won't be able to control the
receiver with your computer, but--at least in my case--the trade off
was well worth it.

On Fri, 20 Jan 2006 07:52:03 -0500, "Robert11"
wrote:

Hi,

Do receiving only (30 MHz on down) and presently just have a random length
wire running around attic.
Will be putting up an outside antenna once things warm up a bit.

Was wondering about household type of noise sources.

Not sure if the noise I'm picking up now is mainly from household sources
or atmospheric.
Other than turning stuff on and off, any easy way way to tell ?

Anyway, regarding household noise (other than on-off type of transients):

I imagine that the 60 Hz power stuff isn't much of a problem seeing where
most of the
listening is done.
Is this generally true, or are the higher order harmonics a problem ?

So, where is most of the noise coming from:
Is it Mainly from:

PC's
broadband cable modems
small 120 to 12 V type of wal-warts
Or,... ?

Any filters or other approaches to minimize ?

Trying to get a good understanding on this: How quickly do the fields from
these sources diminish with distance
(I would imagine very quickly, but am not sure) ?

Thanks,
Bob


Dimmers. Halogen lamps. Miniature neon lamps (doorbell buttons,
fish-tank heaters). Old fashioned fluorescent lamps. Neon lighting.
Electric blankets. Waterbed heaters.

Who sells ferrite beads,websites Please? Concerning computers,I wonder
if making some Faraday cages (for computer and computer monitor) out of
some easy to shape and form close weave copper screen wire would help?
Something that can easily be placed over (and removed for when using
computer and computer monitor) computer and computer monitor and perhaps
shape some copper screen wire around whatever computer related
cables/wires would be of any help with decreasing RFI? Well,it's a
thought anyway,I guess.Hey,I certainly am not an expert on that.
cuhulin

wrote in message
...
Who sells ferrite beads,websites Please? Concerning computers,I wonder
if making some Faraday cages (for computer and computer monitor) out of
some easy to shape and form close weave copper screen wire would help?
Something that can easily be placed over (and removed for when using
computer and computer monitor) computer and computer monitor and perhaps
shape some copper screen wire around whatever computer related
cables/wires would be of any help with decreasing RFI? Well,it's a
thought anyway,I guess.Hey,I certainly am not an expert on that.
cuhulin

This would do nothing to diminish the H field.

W4OP

PC's
broadband cable modems
small 120 to 12 V type of wal-warts
Or,... ?

All of the above. But some comments:

Monitors can make a lot of harmonic hash throughout the HF spectrum.
TV's don't seem quite so bad in general (3.58MHz and harmonics are of
course a problem!) and I don't know much about HDTV's etc.

Most wall-warts don't make a lot of noise, but small switching supplies
are an exception.

Fluorescent lamps and dimmers can make an awful racket. Electronic
ballasts make a qualitatively different kind of hash than magnetic
ballasts. Some low-voltage DC lighting and halogen lamps make
incredible noise, I have no idea why (maybe a built-in dimmer?)

Ethernet cabling running around the house can make some, especially
concentrated at 10MHz and harmonics.

Noise can be conducted over and radiated by power cables, ethernet
cables, video cables, keyboard cables, etc.

Motors can always be a source. Kitchen appliances are awful but not
usually run for more than a few minutes at a time. Vacuum cleaners can
be almost as bad. Furnace blowers, AC compressors, refrigerator
compressors aren't as awful but in a modern house at least one of these
is probably running somewhere.

Sometimes I fantasize about moving out to the middle of nowhere, where
there is no power grid!

Tim.

"Robert11" wrote in message
...
Hi,

Do receiving only (30 MHz on down) and presently just have a random length
wire running around attic.
Will be putting up an outside antenna once things warm up a bit.

Was wondering about household type of noise sources.

Not sure if the noise I'm picking up now is mainly from household sources
or atmospheric.
Other than turning stuff on and off, any easy way way to tell ?

Turning stuff on and off is the easiest way to tell
if it is making noise.


Anyway, regarding household noise (other than on-off type of transients):

I imagine that the 60 Hz power stuff isn't much of a problem seeing where
most of the
listening is done.
Is this generally true, or are the higher order harmonics a problem ?

So, where is most of the noise coming from:
Is it Mainly from:

PC's
broadband cable modems
small 120 to 12 V type of wal-warts
Or,... ?

Any filters or other approaches to minimize ?

Trying to get a good understanding on this: How quickly do the fields
from these sources diminish with distance
(I would imagine very quickly, but am not sure) ?

1/r^2


Thanks,
Bob

I've got a Sony component AM/FM/stereo amplifier
that makes a fair amount of noise whenever it it
plugged in. (Switch-mode power supply with
poor filtering apparently.)

The computer monitor makes a fair amount of
noise too. (It is hard to shield a CRT.)

I haven't specifically tracked down
other sources in the house.
The situation was pretty poor when I just had
an indoor antenna.
So I quickly put up an outdoor antenna with
coaxial feed. That made a big difference.

I still hear some low level noise spaced every
62 kHz or so throughout the HF band.
It is not in my house but it might be in
the neighborhood.
Some day I'll get a directional antenna and
portable receiver and track it down.

--
rb

In article ,
Ron Baker, Pluralitas! wrote:

I still hear some low level noise spaced every
62 kHz or so throughout the HF band.
It is not in my house but it might be in
the neighborhood.
Some day I'll get a directional antenna and
portable receiver and track it down.

A VGA display running at one of the lower res 31 kHz horizontal scan rates.

Mark Zenier
Googleproofaddress(account:mzenier provider:eskimo domain:com)

In article ,
"Robert11" wrote:

Hi,

Any idea how quickly in distance these household noise generated fields
diminish to values unlikely to be picked up ?

Snip

This is a complex question. Firstly to consider is that there is two
types of noise sources or ways for noise to find its way to your radio:

1. RFI, radio frequency interference, which is radiated noise. Radiated
noise can travel long distance and is an example of the signals you want
to receive.

2. EMI, electromotive interference, which is conducted noise. As
separate local electric and magnetic fields the energy falls off rapidly
over distance. A few feet can make a big difference in noise level.

If the problem electronic device is radiating the noise (RFI) then how
much it bothers your reception will be determined by how much noise it
generates and how efficiently it radiates that noise. Generally the
dimensions of the device mean that any radiators in the device will be
electrically small and the efficiency the device to radiate noise
energy will be poor. The result is most of the noise energy will become
localized electric and magnetic fields known as inductive fields as
opposed to what is know as a far field EM wave. The radiated EM wave
has a special relationship between the electric and magnetic component
fields that allow the long distance propagation to occur. The localized
electric fields tend to spread out more than the magnetic fields in the
low dielectric air and the majority of non metallic house building
materials slow them down by tending to bend them but don't stop them.
The result is that the inside of most homes are much noisier inside
then just a few feet outside most structures.

So you can draw several conclusions from this such as that the local
noise field energy will fall off rapidly over distance from the noise
source. This means that you can reduce noise by moving a portable radio
or antenna farther away from the source. Antennas that are sensitive to
the magnetic component and not the electric component on the EM noise
fields will fare better than an antenna that is an electric field type
in the area of local noise sources. A common mode electric field antenna
will the worst performing antenna around local noise sources.

If the main noise generation is EMI meaning that the noise is conducted
down the power cord into the AC mains supply then several things can
happen:

A. If you plug your radio into the AC mains supply then the noise goes
up the radios power cord and is conducted into the radio.

B. In addition to this direct conduction if you have an external antenna
connect by coax cable this noise can be further conducted on the outer
shield and then transfer to the antenna as common mode energy.

C. Noise that starts out as EMI in the mains AC supply now has found
larger radiators, which is the wiring in your house and then can radiate
more efficiently becoming RFI.

"C" can be an especially insidious problem to solve.

Strategy to follow to reduce local noise:

1. Put as much distance as you can between the radio, antenna and the
local noise sources.

2. Use an antenna type sensitive to the Magnetic component of a EM wave.

3. Use RF chokes on noise source device power cord and other cables.

4. Turn off and actually disconnect electronic noise sources.

5. Identify troublesome noise sources by unplugging or disconnecting
everything in the house and turn them on one at a time after a scan on
the radio.

6. Use chokes on the coax to the antenna or choose a lossy RF path for
the coax such as putting it in the ground on its way to the antenna from
the house.

7. Locate external antennas away from power lines, the house and
neighbors homes or other noise sources.

--
Telamon
Ventura, California

Telamon wrote:

2. EMI, electromotive interference, which is conducted noise. As
separate local electric and magnetic fields the energy falls off rapidly
over distance. A few feet can make a big difference in noise level.




I think we're confusing EMF (Electromotive Force), also known as Voltage
with EMI (Electro magnetic interference).


Good posting, though...





mike