Ferrite chokes.
 

Hello.

I need some help from you.

I live in a big city and shortwave is very noisy. But the main noise
comes from my own house, specially the computers.

I have been trying to reduce the interferences using ferrite and iron
powder chokes.

I have been playing with two kind of chokes: one is the typical toroidal
iron powder, painted choke, and the other is like a ferrite choke in a
hollow cylinder, divided in two part in a plastic case, that can be put
in a cable without disconnecting it.

Some noises are reduced best when I use the torodial choke (like in the
AC currect cable to the receiver) and other noises are reduced with the
cylindrical choke (like in the computer cables, specially the keyboard).

I prefer the cylindrial ones because it is much easier to put. For
keyboard cable, it works great, so I plan to buy some in a electronic shop.

Can you give me some recommendations about them? I want to buy some big
and some small (if they are cheap, I don't know the price). For the
keyboard of my brother's computer, with one cylindrical the noise
disappears (it is two rooms far) but my computer needs more ;) with one
cylinder the noise is reduced but doesn't disappear, as it is much nearer.

Any recommendation will be great.


Thanks a lot.

"Nacho" wrote in message
...

[snip]


Can you give me some recommendations about them? I want to buy some big
and some small (if they are cheap, I don't know the price). For the
keyboard of my brother's computer, with one cylindrical the noise
disappears (it is two rooms far) but my computer needs more ;) with one
cylinder the noise is reduced but doesn't disappear, as it is much nearer.

Any recommendation will be great.


Thanks a lot.


Marlin P Jones offers several split core ferrites:

http://www.mpja.com/listitems.asp?dept=157&main=110

They are more expensive at Radio Shack:

http://www.radioshack.com/search.asp...search&SR C=1

Frank Dresser

Hi Frank.

Thanks for the shops but I was asking for information about what kind of
chokes to use, more than where to buy them ( I will buy them in a local
shop in Spain)

Thanks anyway!

Best regards.


Frank Dresser wrote:
"Nacho" wrote in message
...

[snip]


Can you give me some recommendations about them? I want to buy some big
and some small (if they are cheap, I don't know the price). For the
keyboard of my brother's computer, with one cylindrical the noise
disappears (it is two rooms far) but my computer needs more ;) with one
cylinder the noise is reduced but doesn't disappear, as it is much nearer.

Any recommendation will be great.


Thanks a lot.



Marlin P Jones offers several split core ferrites:

http://www.mpja.com/listitems.asp?dept=157&main=110

They are more expensive at Radio Shack:

http://www.radioshack.com/search.asp...search&SR C=1

Frank Dresser

In article , Nacho
wrote:

Hello.

I need some help from you.

I live in a big city and shortwave is very noisy. But the main noise
comes from my own house, specially the computers.

I have been trying to reduce the interferences using ferrite and iron
powder chokes.

I have been playing with two kind of chokes: one is the typical
toroidal iron powder, painted choke, and the other is like a ferrite
choke in a hollow cylinder, divided in two part in a plastic case,
that can be put in a cable without disconnecting it.

Some noises are reduced best when I use the torodial choke (like in
the AC currect cable to the receiver) and other noises are reduced
with the cylindrical choke (like in the computer cables, specially
the keyboard).

I prefer the cylindrial ones because it is much easier to put. For
keyboard cable, it works great, so I plan to buy some in a electronic
shop.

Can you give me some recommendations about them? I want to buy some
big and some small (if they are cheap, I don't know the price). For
the keyboard of my brother's computer, with one cylindrical the noise
disappears (it is two rooms far) but my computer needs more ;) with
one cylinder the noise is reduced but doesn't disappear, as it is
much nearer.

Any recommendation will be great.

Go for the Ferrite as it has more inductance per turn since you only
have one to three turns at best depending on type.

Not any ferrite will do. You need to look at its specifications so the
needed inductance will be in the frequency range you are interested in
blocking.

The cylindrical ones are good from the stand point of the input to
output has greater separation so the noise has a harder time making it
around the core.

If you are going to put more than one core on a electrical cord start
with them on both ends since there could be drivers on both ends like
on my computer.

Good luck in improving your reception.

--
Telamon
Ventura, California

Hello Telamon.

Thanks for your reply.

Just a question, you say "the needed inductance will be in the frequency
range you are interested in blocking", but what is the needed
inductance? As high as possible, a low as possible, a defined value?

I have seen things like "Impedance: 100 at 25MHz, 200 at 100MHz". I'm
only interested in lower frequencies, in the shortwave band.. Also
bigger ferrites has higher inductace.


Thanks!

Best regards.


Telamon wrote:
In article , Nacho
wrote:


Hello.

I need some help from you.

I live in a big city and shortwave is very noisy. But the main noise
comes from my own house, specially the computers.

I have been trying to reduce the interferences using ferrite and iron
powder chokes.

I have been playing with two kind of chokes: one is the typical
toroidal iron powder, painted choke, and the other is like a ferrite
choke in a hollow cylinder, divided in two part in a plastic case,
that can be put in a cable without disconnecting it.

Some noises are reduced best when I use the torodial choke (like in
the AC currect cable to the receiver) and other noises are reduced
with the cylindrical choke (like in the computer cables, specially
the keyboard).

I prefer the cylindrial ones because it is much easier to put. For
keyboard cable, it works great, so I plan to buy some in a electronic
shop.

Can you give me some recommendations about them? I want to buy some
big and some small (if they are cheap, I don't know the price). For
the keyboard of my brother's computer, with one cylindrical the noise
disappears (it is two rooms far) but my computer needs more ;) with
one cylinder the noise is reduced but doesn't disappear, as it is
much nearer.

Any recommendation will be great.


Go for the Ferrite as it has more inductance per turn since you only
have one to three turns at best depending on type.

Not any ferrite will do. You need to look at its specifications so the
needed inductance will be in the frequency range you are interested in
blocking.

The cylindrical ones are good from the stand point of the input to
output has greater separation so the noise has a harder time making it
around the core.

If you are going to put more than one core on a electrical cord start
with them on both ends since there could be drivers on both ends like
on my computer.

Good luck in improving your reception.

In article ,
Nacho wrote:

Hello Telamon.

Thanks for your reply.

Just a question, you say "the needed inductance will be in the frequency
range you are interested in blocking", but what is the needed
inductance? As high as possible, a low as possible, a defined value?

I have seen things like "Impedance: 100 at 25MHz, 200 at 100MHz". I'm
only interested in lower frequencies, in the shortwave band.. Also
bigger ferrites has higher inductace.

You want the most inductance you can get. That's why you want to use the
ferrite. Impedance here is inductive reactance.

Impedance = 2 * pi * F * L

2 times pi times the frequency times the inductance

--
Telamon
Ventura, California

Thanks!

I will go soon to the shop to ask for some ;) I hope they are not too
expensive! I'm going to shield all the cords at home...

Best regards.


Telamon wrote:
In article ,
Nacho wrote:


Hello Telamon.

Thanks for your reply.

Just a question, you say "the needed inductance will be in the frequency
range you are interested in blocking", but what is the needed
inductance? As high as possible, a low as possible, a defined value?

I have seen things like "Impedance: 100 at 25MHz, 200 at 100MHz". I'm
only interested in lower frequencies, in the shortwave band.. Also
bigger ferrites has higher inductace.


You want the most inductance you can get. That's why you want to use the
ferrite. Impedance here is inductive reactance.

Impedance = 2 * pi * F * L

2 times pi times the frequency times the inductance

Nacho wrote in message ...
Hello.

I need some help from you.

I live in a big city and shortwave is very noisy. But the main noise
comes from my own house, specially the computers.

I have been trying to reduce the interferences using ferrite and iron
powder chokes.

I have been playing with two kind of chokes: one is the typical toroidal
iron powder, painted choke, and the other is like a ferrite choke in a
hollow cylinder, divided in two part in a plastic case, that can be put
in a cable without disconnecting it.

Some noises are reduced best when I use the torodial choke (like in the
AC currect cable to the receiver) and other noises are reduced with the
cylindrical choke (like in the computer cables, specially the keyboard).

I prefer the cylindrial ones because it is much easier to put. For
keyboard cable, it works great, so I plan to buy some in a electronic shop.

Can you give me some recommendations about them? I want to buy some big
and some small (if they are cheap, I don't know the price). For the
keyboard of my brother's computer, with one cylindrical the noise
disappears (it is two rooms far) but my computer needs more ;) with one
cylinder the noise is reduced but doesn't disappear, as it is much nearer.

Any recommendation will be great.


Thanks a lot.

It might be well worth your time and saved money to find all the local
shops that work on PCs. A lot of dead PC subsystems will have ferrite
that can be used for RFI/EMI control. Most monitors have a big ferrite
choke on the video line. And have several more inside. Dead switch
mode power supplies often have several ferrite chokes inside them.
Even keyboards and mouse often have ferrite chokes inside. I have
salvaged many usefull pieces of ferrite from otherwise useless and
dead PC "stuff".
Even modern consumer devices like CD players, TV sets, heck, almost
anything
with a micro-controller inside will have at least one ferrite choke
inside!
Good luck and happy hunting!
Terry