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  #1 (permalink)  
Old 06-18-2017, 12:19 PM
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Default Which Toroids for Wrapping Antenna and USB Cables?

I would like to wrap my USB cables and perhaps antenna cables with toroids to reduce noise.

What is the appropriate type and number of toroids to effectively reduce interference?

Is it EMI suppression that is need or?

Make, model number, and if possible - where to get them please.
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Old 06-18-2017, 10:37 PM
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What frequency range do you want to reduce? For HF 2-30Mhz range wrapping 8 to 10 turns of most cables like AC power, speaker, Ethernet, RG-58 coax, etc, around an FT-240-31 core does a good job. The very best price I've found on these is here: https://proaudioeng.com/fair-rite-2-...3-toroid-core/

For smaller cables like USB, about 5 turns around one of these works well from about 2 to 30MHz: https://proaudioeng.com/fair-rite-0-...ite-snap-core/

For VHF/UHF about three of these snapped over a small dia cable works well: 2x31-3951p2 - Amidon and for large dia cables: 2X43-351P2 - Amidon

If you have a big problem its best to identify what the source is and what its fundamental frequency is. Sometimes a power supply switching at 30KHz will cause problems throughout the HF range and using a different mix ferrite like 77 or ?? will give better results.

For serious noise problems it might be good to call Bob at Palomar Engineering and discuss your noise problem with him. They sell the same ferrites as anyone else and at a higher price, but if you need an experienced person to help diagnose and recommend a particular ferrite its worth the extra $$.
prcguy



Quote:
Originally Posted by ultravista View Post
I would like to wrap my USB cables and perhaps antenna cables with toroids to reduce noise.

What is the appropriate type and number of toroids to effectively reduce interference?

Is it EMI suppression that is need or?

Make, model number, and if possible - where to get them please.
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  #3 (permalink)  
Old 06-19-2017, 8:39 AM
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prcguy - I am trying to eliminate the spikes such as those seen in the screenshots. The interference is evenly spaced and patterned.

In the second and third screenshots, It looks as if they are evenly at spaced 60 cycles.

I am most interested in 2-30Mhz range, sometimes <1Mhz.

The RTL dongle is attached to a rear USB plug and extended to the front with a small 2ft cable.

For the USB cable 'around 5 turns' do you mean 5 snap-on toroids at one end or each end of the cable? How do you wrap around the snap-on core?
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  #4 (permalink)  
Old 06-19-2017, 12:16 PM
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First you should identify what is causing all the spikes. Run your RTL from a battery powered laptop with no power supply then turn off everything in the house one by one to see if the noise goes away. Hopefully the problem is within your house so you can deal with it. If its not something in your house and under your control I doubt you can do much to eliminate it.

Once you find whats causing the noise then apply the best treatment depending on what it is and ferrite cores may not always fix it.

For the snap on cores you open the core then wrap the wire around one half the core across the space provided for wires leaving space to close the core without squishing the wires. Each time a wire passes through the core its considered one turn.
prcguy


Quote:
Originally Posted by ultravista View Post
prcguy - I am trying to eliminate the spikes such as those seen in the screenshots. The interference is evenly spaced and patterned.

In the second and third screenshots, It looks as if they are evenly at spaced 60 cycles.

I am most interested in 2-30Mhz range, sometimes <1Mhz.

The RTL dongle is attached to a rear USB plug and extended to the front with a small 2ft cable.

For the USB cable 'around 5 turns' do you mean 5 snap-on toroids at one end or each end of the cable? How do you wrap around the snap-on core?
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  #5 (permalink)  
Old 06-19-2017, 12:34 PM
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I had pretty much the same problem. With 3 PCs and tons of other things in the room I tried a bunch of things.

The least of which was the clamp on cores like prcguy said. These 'seem' to work. But with so much stuff in my room as I said it was hard to pin down exactly what the problem was.

I armed myself with a hand held AM radio and started the hunt. Although the frequencies you say are in the 11 MHZ range, the AM radio did find some pretty loud noises as I moved the radio around the room.

Believe it or not the biggest interference was from my FIOS ethernet cable. I know, that sounds crazy.

If you want to check it out, the snap ons I found here:

Ring Core Ferrite Bead Clamp Choke Coil RFI EMI Noise Suppressor Snap Cable Clip | eBay

Single cores I used are here:

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

If nothing else, get those snap ons. Put them on everything you own.

Hope this helps. It did for my inside noise. Outside interference was another story.
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