Friends -

I have a few queries regarding people's experience with Ferrite, esp.
beads and so forth.

Can these things actually reduce noise? I see them suggested for
encircling coax cable, electrical wires on appliances and electronics,
and many other devices. If one were to put them around a coax cable,
how many would one use in a row?

I have also seen suggestions that ferrite cores with the offending
wires wound through them are useful as well - how do these compare to
beads?

If one wound a wire around a ferrite rod, would this also have a
similar effect?

I presently use an A-D DX-Ultra, have used random wires, and intend to
put up some more wire including a new random wire and probably a loop
encircling most of my property along the fence and roof eaves. I
expect to feed these wires using coax with matching tranformers. The
radio and accessories are grounded, which clearly increases both the
signal and external noise.

I appreciate any and all answers. The noise in my neighborhood,
mostly the result of artificial external problems, is really
discouraging, and if these things would help even a few dB, it would
be a blessing.

Many thanks,
Bruce Jensen

I have a few queries regarding people's experience with Ferrite, esp.
beads and so forth.

Can these things actually reduce noise?

I once had HUGE computer noise in my ham shack. My
computer made so much hash that there were only tiny
segments in each band where the noise was outside the
passband of my filters, and I could work weak signal CW.

Then someone told me to put ferrite on all the computer
wires. I bought some surplus (Mitel was the brand, from
I believe All Electronics or some such) snap-on ferrite
gizmos. I put one on the monitor cable - Hmmmmm....
lesss noise. So I put one on the mouse cable, the keyboard
cable, the speaker wires, etc. The more I put them on
the wires the quieter things got. Then I added one on
EACH END of each wire - it's now virtually silent in
my ham shack from that computer.

So in my case? Yeah - they made a HUGE difference.

Dave

bpnjensen wrote:

Friends -

I have a few queries regarding people's experience with Ferrite, esp.
beads and so forth.

Can these things actually reduce noise? I see them suggested for
encircling coax cable, electrical wires on appliances and electronics,
and many other devices. If one were to put them around a coax cable,
how many would one use in a row?

I have also seen suggestions that ferrite cores with the offending
wires wound through them are useful as well - how do these compare to
beads?

If one wound a wire around a ferrite rod, would this also have a
similar effect?

I presently use an A-D DX-Ultra, have used random wires, and intend to
put up some more wire including a new random wire and probably a loop
encircling most of my property along the fence and roof eaves. I
expect to feed these wires using coax with matching tranformers. The
radio and accessories are grounded, which clearly increases both the
signal and external noise.

I appreciate any and all answers. The noise in my neighborhood,
mostly the result of artificial external problems, is really
discouraging, and if these things would help even a few dB, it would
be a blessing.

Many thanks,
Bruce Jensen

Hi Bruce

If you've got an RFI problem, ferrite beads or cores are a big help.

If your antenna is away from the house, and your radio is well shielded,
I'd put one on the power cable to the radio, and three on the coax -
one near the radio end, one near the antenna end, and one outside near
the house.

If your radio isn't well shielded, or your antenna is in or near the
house you might want to buy them in bulk and put one on every power cord
near the plug, and a second on the other end of anything that causes RFI.

Good luck.

In article ,
(bpnjensen) wrote:

Friends -

I have a few queries regarding people's experience with Ferrite, esp.
beads and so forth.

Can these things actually reduce noise? I see them suggested for
encircling coax cable, electrical wires on appliances and
electronics, and many other devices. If one were to put them around
a coax cable, how many would one use in a row?

Yes they can help. Clamped around a cable they are a 1 turn choke coil.
How many you need depend upon how much attenuation you need. The more
noise you have the larger a choke you will need.

The idea here is that you have noise traveling the outside of cables or
coax and you are attempting to stop it by inserting inductive reactance
in the path.

I have also seen suggestions that ferrite cores with the offending
wires wound through them are useful as well - how do these compare to
beads?

I'm not sure exactly what you are referring to as a "core" and "beads."
I'll guess that you mean the two piece snap together as the "core" and
a toroid as the "bead." They work the same way. The one piece core is
more reliable in that you must make sure that the two piece units fit
snugly together with no gap between them or they become non-effective.

If one wound a wire around a ferrite rod, would this also have a
similar effect?

Yes. The closed cores will work better from the standpoint that their
magnetic path is closed. No stray fields with the closed core type.

What ever type of core used make sure to keep the ends away from each
other or you will make the choke non-effective.

I presently use an A-D DX-Ultra, have used random wires, and intend
to put up some more wire including a new random wire and probably a
loop encircling most of my property along the fence and roof eaves.
I expect to feed these wires using coax with matching tranformers.
The radio and accessories are grounded, which clearly increases both
the signal and external noise.

I appreciate any and all answers. The noise in my neighborhood,
mostly the result of artificial external problems, is really
discouraging, and if these things would help even a few dB, it would
be a blessing.

Generally what you are trying to accomplish with the chokes on the coax
to the antenna is to stop noise coming from the radio end (which is
connected to the AC noisy mains) from getting to the antenna. Noise
traveling from the radio to the antenna couples to the antenna and
mixes with any received signal back down the center conductor.

If you don't have a noisy AC mains supply, radio or the coax shield over
its run is not picking up noise then the chokes will not do much for you.

Often these chokes are used on the source of noise generating appliances
to stop them from radiating.

--
Telamon
Ventura, California

Thanks to Dave, Mark and Telemon - all very interesting and useful
suggestions. Once I get the wires up, I will try some of these
configurations. I have never had any problem that I could trace back
to, say, my PC or my TV, but maybe the beads will help clarify whether
these are problems.

Telemon, when I differentiated between beads and cores, I guess I
meant to differentiate between mounting styles - I think of beads as
"slipped over" the cord, while I think of "cores" as being
doughnut-shaped toroids through which the cords are "wound" several
turns.

It sounds like the beads or toroids would function better than the
rods for most RFI suppression purposes. Per Mark and Dave, it also
sounds like the more beads used, the better isolation one can achieve.

From what I gather, in addition to the specific points that each of
you made, the AC mains and RFI noise that the ferrites will help to
overcome is usually very local in nature, typically generated at one's
own house or *maybe* with one's immediate neighbor. It sounds like
they might be less effective on RFI picked up directly by the antenna
from, say, a scratchy high-voltage power line 150 yards away, or a bad
streetlight down the block, or the like.

Oh, to live back in rural Massachusetts again...I remember quiet
airwaves...

Thanks!
Bruce

bpnjensen wrote:

Thanks to Dave, Mark and Telemon - all very interesting and useful
suggestions. Once I get the wires up, I will try some of these
configurations. I have never had any problem that I could trace back
to, say, my PC or my TV, but maybe the beads will help clarify whether
these are problems.

Telemon, when I differentiated between beads and cores, I guess I
meant to differentiate between mounting styles - I think of beads as
"slipped over" the cord, while I think of "cores" as being
doughnut-shaped toroids through which the cords are "wound" several
turns.

It sounds like the beads or toroids would function better than the
rods for most RFI suppression purposes. Per Mark and Dave, it also
sounds like the more beads used, the better isolation one can achieve.

From what I gather, in addition to the specific points that each of
you made, the AC mains and RFI noise that the ferrites will help to
overcome is usually very local in nature, typically generated at one's
own house or *maybe* with one's immediate neighbor. It sounds like
they might be less effective on RFI picked up directly by the antenna
from, say, a scratchy high-voltage power line 150 yards away, or a bad
streetlight down the block, or the like.

Oh, to live back in rural Massachusetts again...I remember quiet
airwaves...

Thanks!
Bruce

Noise from an arcing power line transformer can be nasty as it's a broadband transmitter with plenty of power connected to lots of wire.

Took me months to get them to replace the transformer across the street from my house. In round numbers, it was 150 feet from the closest antenna, and still made that antenna useless. The antenna that was a little over 400 feet away from it still picked
up some noise.

I do think putting your antenna as far as possible from noise sources is the best way to go. Running your coax underground is also helpful.

But mostly, you just need to look at what you have to work with on your property, and figure out how to make the most of it.

Good luck.

"Mark S. Holden" wrote:

bpnjensen wrote:

Thanks to Dave, Mark and Telemon - all very interesting and useful
suggestions. Once I get the wires up, I will try some of these
configurations. I have never had any problem that I could trace back
to, say, my PC or my TV, but maybe the beads will help clarify whether
these are problems.

Telemon, when I differentiated between beads and cores, I guess I
meant to differentiate between mounting styles - I think of beads as
"slipped over" the cord, while I think of "cores" as being
doughnut-shaped toroids through which the cords are "wound" several
turns.

It sounds like the beads or toroids would function better than the
rods for most RFI suppression purposes. Per Mark and Dave, it also
sounds like the more beads used, the better isolation one can achieve.

From what I gather, in addition to the specific points that each of
you made, the AC mains and RFI noise that the ferrites will help to
overcome is usually very local in nature, typically generated at one's
own house or *maybe* with one's immediate neighbor. It sounds like
they might be less effective on RFI picked up directly by the antenna
from, say, a scratchy high-voltage power line 150 yards away, or a bad
streetlight down the block, or the like.

Oh, to live back in rural Massachusetts again...I remember quiet
airwaves...

Thanks!
Bruce

Noise from an arcing power line transformer can be nasty as it's a broadband transmitter with plenty of power connected to lots of wire.

Took me months to get them to replace the transformer across the street from my house. In round numbers, it was 150 feet from the closest antenna, and still made that antenna useless. The antenna that was a little over 400 feet away from it still picked
up some noise.

I do think putting your antenna as far as possible from noise sources is the best way to go. Running your coax underground is also helpful.

But mostly, you just need to look at what you have to work with on your property, and figure out how to make the most of it.

I've had a problem here since June, but the local BPW is working on it, but can't quite seem to locate the problem.

After a conversation with the Director of Electrical Services here yesterday it would seem as though they are bringing in some outside help.

They've tried here with some sophisticated sniffing equipment, both RF and ultrasonic.

My good fortune here has been that the Director is a Extra Class amateur and understands what the problem is causing.

We successfully fixed a problem similar to the one I'm currently experiencing last Fall in about 3 weeks. It involved replacing several thousand dollars of worth of equipment, and I'd suspect that this problem will require the same.

If they don't fix it soon, I suspect they'll be paying for a few trips up to the northern dx'ing site, and they've been informed of this!

dxAce
Michigan

http://www.iserv.net/~n8kdv/dxpage.htm

"Mark S. Holden" wrote in message
...
bpnjensen wrote:



Hi Bruce

If you've got an RFI problem, ferrite beads or cores are a big help.

If your antenna is away from the house, and your radio is well shielded,
I'd put one on the power cable to the radio, and three on the coax -
one near the radio end, one near the antenna end, and one outside near
the house.

If your radio isn't well shielded, or your antenna is in or near the
house you might want to buy them in bulk and put one on every power cord
near the plug, and a second on the other end of anything that causes RFI.

Good luck.






Marlin P Jones is a good bulk supplier, especially if you want around 1000
of something:

http://www.mpja.com/category/Chokes_..._&_Filters.asp

Frank Dresser

Frank Dresser wrote:

"Mark S. Holden" wrote in message
...
bpnjensen wrote:



Hi Bruce

If you've got an RFI problem, ferrite beads or cores are a big help.

If your antenna is away from the house, and your radio is well shielded,
I'd put one on the power cable to the radio, and three on the coax -
one near the radio end, one near the antenna end, and one outside near
the house.

If your radio isn't well shielded, or your antenna is in or near the
house you might want to buy them in bulk and put one on every power cord
near the plug, and a second on the other end of anything that causes RFI.

Good luck.






Marlin P Jones is a good bulk supplier, especially if you want around 1000
of something:

http://www.mpja.com/category/Chokes_..._&_Filters.asp

Here's another good supplier, I've purchased all my beads from this outfit over
the years:

http://www.amidoncorp.com/

dxAce

On the cutting edge.