Tubular Ferrites On Cables: Questions On ?

[BOBRR]

Hi,

Not sure if this is the best Forum to Post to, or not. If not, please let me know.

I have two receivers that I use in a small Study area.
A winRadio G-31 Excalibur, and a SDRPlay RSP-2
Only do SW listening; no transmitting.

Hard to tell, but there is likely a lot of RF noise from 3 computer monitors, pc's, etc. in the room.

Have never thought about this much, but realize I don't have a good understanding of
how the ferrite tubular (chokes ?) on the short cables that came with both radios function.

Is it to help prevent the radio to pc cables picking up "more" noise, or is it the opposite in that they
work to prevent even more radiated noise (even though they are just receivers) ?

From these short cables with the ferrites that came with the receivers, I have about
8 foot USB extension cables to reach where the pc is.

Questions: Should I add even more ferrites to this extension section ?

Where: one on eeach end of the extension cable ?

More better ? Load up the extension cables with several ?

If I do buy more, any particular brands good, or any I should stay away from ?

As always, much thanks,
Bob

 

[bob550]

What type of antenna are you using? Interior or exterior? What type of lead-in do you use from your antenna, shielded coax cable or wire? Ferrites do serve a purpose in reducing some types of interference entering your cables. Ferrites can be more effective if you install the ferrite around cable that has been looped. Try installing them on the monitor data cables as well. Experimentally, you can install more ferrites, but that may not be the answer. The interference could also be entering the receivers directly as well. If you suspect a monitor is causing your problem, turn the monitor off and see if the interference is eliminated. I've had monitor interference that seemed to affect the 31 meter band in particular. Other than that, there could be several possible causes of RFI in the average radio shack. Switching power supplies (wall warts) are notorious for this. Routers and cable modems can also cause RFI. In any case, careful experimentation can point to the source of your troubles.

 

[nd5y]

All you ever wanted to know about ferrite beads and chokes.
http://audiosystemsgroup.com/RFI-Ham.pdf
http://www.yccc.org/Articles/W1HIS/CommonModeChokesW1HIS2006Apr06.pdf
The Proper Split Beads to Suppress RFI

 

[cmdrwill]

Also Palomar Engineers, Bob IS the go to guy on ferrites.

 

[BOBRR]

Hi,

Real good "stuff".
Much thanks; appreciate the help and the info.

Regards,
Bob

 

[RFI-EMI-GUY]

Unless you keep your antennas away from your computer's entirely you are going to be suffering from the noise. My computer screens, one of them anyway, radiates signals in the 462 MHz range. It is coming from the monitor screen itself, no amount of ferrite is going to fix it. Wrapping in aluminum foil, might, but I won't be able to see the screen.

Sent from my SM-T350 using Tapatalk

 

[BOBRR]

Hi,
Again, thanks for help.
Will blame my ignorance on "old age' now.
Great excuse for most everything, I've found.

I do receive only.
Have an outside long wire antenna, a balun, and then a relatively long run of coax into mySDR receiver (SDRPlay RSP-2)

Question followup:

Is the optium/correct placements for these ferrite chokes on the noise source wiring like a pc monitor (input and outputs ?),
or on the cables going into the device you want to prevent noise pickup into ?

Both ?

If on the source device, e.g., a pc monitor, on the power supply feeding, and also the HDMI cable to the pc ?

Thanks,
Bob

 

[bob550]

Have an outside long wire antenna, a balun, and then a relatively long run of coax into mySDR receiver (SDRPlay RSP-2)

That sounds like a mirror image of my own antenna setup. What type of cable are you using, and is your balun grounded? Regarding the placement of the ferrites is concerned, experimentation can help you make that determination. Try disconnecting the monitor data cable while leaving the monitor on to see if the interference is eliminated. If so, place the ferrites on that cable. Try a different refresh rate for your monitors. Try placing some ferrites on the incoming antenna cable near either receiver, and/or on the USB cable at the input to the receivers. Just make sure the ferrite beads are sized for the cable you're installing them on so the fit is tight.

 

[cmdrwill]

RFI/EMI Solutions - Palomar Engineers®

 

[prcguy]

I would identify any and all sources of noise before trying to tame it with ferrite, otherwise you will be spending a lot of extra time for possibly no benefit. Look for noise or go to frequencies that you know have a noise problem, then turn off everything in the house one by one to see what is making any noise in your receiver.

After finding an item that makes noise you can go deeper, like when the computer is on you have noise, so eliminate the keyboard, mouse, USB, Ethernet connections until you find the actual noise maker. Then apply ferrite to that device and adjust to minimize noise.

Hi,
Again, thanks for help.
Will blame my ignorance on "old age' now.
Great excuse for most everything, I've found.

I do receive only.
Have an outside long wire antenna, a balun, and then a relatively long run of coax into mySDR receiver (SDRPlay RSP-2)

Question followup:

Is the optium/correct placements for these ferrite chokes on the noise source wiring like a pc monitor (input and outputs ?),
or on the cables going into the device you want to prevent noise pickup into ?

Both ?

If on the source device, e.g., a pc monitor, on the power supply feeding, and also the HDMI cable to the pc ?

Thanks,
Bob

 

[BOBRR]

Hi,

Yes, I believe Balun is grounded.
Not sure of coax type.
Both were installed many, many years ago, and it's kinda hard for me to get back outside where
the antenna is to verify. In my 80's now, and back into hobby for the listening only with a new SDRPlay RSP-2.
Quit a toy.

No doubt experimentation as outlined in the post replies is the best way to go, and
will certainly do.

But, am still confused over the most basic of questions:
From a theoretical standpoint, do you want the ferrites on the lines that are radiating the noise,
or on the lines to the receiver etc. where you want to eliminate the noise from entering ?
Or on both ?

Regards, and thanks again,
Bob

 

[prcguy]

Ideally you kill the noise at the source and ferrite would go on the wires that are radiating the noise as close as possible to the noise maker. Once all noise makers are found and fixed with ferrite or other methods, adding a ferrite choke on the antenna coax both at the antenna end and the radio end can further reduce noise.

Noise can be radiated onto the shield of the coax by things in the house where it can travel up to the antenna and be picked up. On my amateur receivers with spectral displays I saw a several dB reduction in noise when I upgraded from a medocre choke at the antnena to a really good one, then I saw a further reduction when I placed one at the radio end. In my case the coax from several radios passes right over some Ethernet cables and next to a wireless router and other junk. These were obviously radiating noise onto the coax and ferrite choke baluns calmed it down.

Hi,

Yes, I believe Balun is grounded.
Not sure of coax type.
Both were installed many, many years ago, and it's kinda hard for me to get back outside where
the antenna is to verify. In my 80's now, and back into hobby for the listening only with a new SDRPlay RSP-2.
Quit a toy.

No doubt experimentation as outlined in the post replies is the best way to go, and
will certainly do.

But, am still confused over the most basic of questions:
From a theoretical standpoint, do you want the ferrites on the lines that are radiating the noise,
or on the lines to the receiver etc. where you want to eliminate the noise from entering ?
Or on both ?

Regards, and thanks again,
Bob