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Author Topic: Getting RFI out of Spectrum Wired / wireless router.  (Read 393 times)

KT0DD

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Getting RFI out of Spectrum Wired / wireless router.
« on: July 31, 2022, 08:56:00 AM »

Hi all, I have no issues with RFI on my PC using the wireless connection, however I'm not a gamer. My "Gamer" grandson has wired ethernet cable from the wifi router to his game console as he didn't like the wireless speeds. He says my 40 meter RF is getting into his game console. I have some Mix 31 / Mix 43 and a few Mix 75 ferrite chokes. One mix 31 is a larger torroid I can wrap several wraps thru. I was going to install a Mix 31 and Mix43 choke right where the etherrnet enters his gaming console, as I work 75-15 meter bands SSB. I was thinking of wrapping the large Mix 31 torroid on the jumper between the modem and wireless router. There are also wall wart power leads to the modem, router and gaming console. Can I wrap both power and ethernet lines thru the same torroids or do I need to keep everything separate? Thanks.

Todd - KT0DD


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K6BRN

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Re: Getting RFI out of Spectrum Wired / wireless router.
« Reply #1 on: July 31, 2022, 10:01:17 AM »

Hi Todd (KT0DD):

I had a similar problem with my son and his equipment and it turned out 40M EMI was getting into the console via the AC line and power supply.  Adding toroids helped to a degree (multiple turns of the AC line cable through a large mix 31 toroid is good), but what "killed" the problem was installing a small isolation transformer in the AC line between the wall plug and console (I had one handy from a swap meet).

His wired ethernet line did not need any help - but his run to the router was short - about 10 feet.

Adding toroids or (most) filters to the ethernet cable can be problematic if it's 100 base-T, gigiabit link or higher speed, because they also attenuate these signals, and in particular, degrade their rise and fall times. 

DX Engineering sells $50 ethernet line filter pairs they claim work with 100 base-T and gigabit ethernet - they may be worth a try if you need them.  They're made to solve just this problem.  Note that they're capacitively coupled filters, not just toroids, and do NOT pass DC, so no "power over ethernet" (POE) devices, like some video cameras, will work with them.  A game console should be fine, though.

https://www.dxengineering.com/parts/dxe-iso-plus-2?seid=dxese1&gclid=Cj0KCQjw0JiXBhCFARIsAOSAKqCfLuTjDaXhwn57JvGXDyxyXKfVkC5HLGLPbYJGyPbBgWx0Sh7jsDEaApIoEALw_wcB

Another possibility may be to try adding a small, inexpensive network switch as a buffer to break up a long ethernet cable run (>20 feet) to the console and increase S/N ratio.  This will also increase latency a bit (important to gamers) and you may need to put ferrites on the DC side of the power "dongle". 

Quote
Can I wrap both power and ethernet lines thru the same torroids or do I need to keep everything separate? Thanks.

In general, you shouldn't do this as you are mixing multiple possible noise sources and the resulting interactions can be unpredictable.  Separate toroids for power and ehternet are recommended, and you should avoid wrapping multiple ethernet lines through the same toroid.  Just my opinion.

Every EMI/RFI problem is unique, so these are some ideas to consider and experiment with - but not a guaranteed solution.

Good luck and let us know how it works out.

Brian - K6BRN

« Last Edit: July 31, 2022, 10:06:56 AM by K6BRN »
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5BWAZ

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Re: Getting RFI out of Spectrum Wired / wireless router.
« Reply #2 on: July 31, 2022, 10:51:10 AM »

I'm also using the Spectrum modem/router combo and have a similar problem which I posted in this forum a few threads below, "40m crashes my internet". VERY frustrating.

I haven't tried adding a "switch" yet, but my next move is probably buying a few longer runs of CAT5 and moving the modem/router to a different part of the house. Hopefully it won't be out of range of a couple of outdoor wifi cameras I'm using.

Maybe the Spectrum gear is just crap, and there's really no fix.

If you find a solution, please post it.

 

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KT0DD

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Re: Getting RFI out of Spectrum Wired / wireless router.
« Reply #3 on: July 31, 2022, 12:27:18 PM »

Hi Todd (KT0DD):

I had a similar problem with my son and his equipment and it turned out 40M EMI was getting into the console via the AC line and power supply.  Adding toroids helped to a degree (multiple turns of the AC line cable through a large mix 31 toroid is good), but what "killed" the problem was installing a small isolation transformer in the AC line between the wall plug and console (I had one handy from a swap meet).

His wired ethernet line did not need any help - but his run to the router was short - about 10 feet.

Adding toroids or (most) filters to the ethernet cable can be problematic if it's 100 base-T, gigiabit link or higher speed, because they also attenuate these signals, and in particular, degrade their rise and fall times. 

DX Engineering sells $50 ethernet line filter pairs they claim work with 100 base-T and gigabit ethernet - they may be worth a try if you need them.  They're made to solve just this problem.  Note that they're capacitively coupled filters, not just toroids, and do NOT pass DC, so no "power over ethernet" (POE) devices, like some video cameras, will work with them.  A game console should be fine, though.

https://www.dxengineering.com/parts/dxe-iso-plus-2?seid=dxese1&gclid=Cj0KCQjw0JiXBhCFARIsAOSAKqCfLuTjDaXhwn57JvGXDyxyXKfVkC5HLGLPbYJGyPbBgWx0Sh7jsDEaApIoEALw_wcB

Another possibility may be to try adding a small, inexpensive network switch as a buffer to break up a long ethernet cable run (>20 feet) to the console and increase S/N ratio.  This will also increase latency a bit (important to gamers) and you may need to put ferrites on the DC side of the power "dongle". 

Quote
Can I wrap both power and ethernet lines thru the same torroids or do I need to keep everything separate? Thanks.

In general, you shouldn't do this as you are mixing multiple possible noise sources and the resulting interactions can be unpredictable.  Separate toroids for power and ehternet are recommended, and you should avoid wrapping multiple ethernet lines through the same toroid.  Just my opinion.

Every EMI/RFI problem is unique, so these are some ideas to consider and experiment with - but not a guaranteed solution.

Good luck and let us know how it works out.

Brian - K6BRN



DX engineering says these work up to Cat 6 ethernet cable. I just ordered a shielded Cat 8 from Amazon. Hope that will still work Thanks.
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W9IQ

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Re: Getting RFI out of Spectrum Wired / wireless router.
« Reply #4 on: July 31, 2022, 12:42:11 PM »

I just ordered a shielded Cat 8 from Amazon. Hope that will still work

If your equipment doesn't provide a ground connection on the side of the RJ-45 jack, that cable may make your problems worse. There are multiple shields, that if left floating, may prove to be an RFI magnet (antenna) depending on the length. It is worth the experiment - just be aware of the potential downside.

On the subject of ferrite, using type 31 along the length of the Ethernet cable will have no negative effect. Each signal within the cable is on a balanced transmission line. The ferrite will only affect common mode current, not the intended differential mode current unless you are extending lines beyond their maximum rated length. Robust Ethernet products include ferrite near or in the jack for this very purpose. You can see such products in the Fair-Rite catalog, for example.

- Glenn W9IQ
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

NA6O

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Re: Getting RFI out of Spectrum Wired / wireless router.
« Reply #5 on: July 31, 2022, 05:36:13 PM »

Glen is correct, as usual. Recommended common-mode choke for ethernet cable is 12 to 14 turns on your mix 31 toroid. Install it close to the router. You need to treat EVERY cable connected to the router, including the power cable. Very long ethernet cables should have a choke installed at both ends. The commercial RFI devices are overpriced…. Buy your toroids from Mouser, Arrow, Digi-Key etc. NOT from the guys with absurd markups like Palomar or DX Engineering. The correct part is Fair-Rite 2631803802.

Gary NA6O
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K6BRN

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Re: Getting RFI out of Spectrum Wired / wireless router.
« Reply #6 on: August 01, 2022, 02:22:02 AM »

On the subject of ferrite, using type 31 along the length of the Ethernet cable will have no negative effect. Each signal within the cable is on a balanced transmission line. The ferrite will only affect common mode current, not the intended differential mode current  - Glenn W9IQ

I stand corrected.  Glen is right (my "brain-fart" - sorry!) - unless there is a major imbalance in the ethernet cable due to issues with the driver/receiver or cable, the differential mode signals should be unaffected by any choke.  No doubt there will be SOME imbalances - but they shouldn't be large.

However, since the balanced, twisted pair lines are tightly coupled in decent CAT5e or better cable, and the receivers and drivers in point to point connections are normally coupled to the cable by (balanced) transformers, common mode current shouldn't be much of an issue either and the chokes shouldn't do much to help OR hurt.

So why use them at all?

"Shouldn't" being the operative word.  Since ham products exist specifically to address ethernet RFI issues, and some of these products are not compatible with POE (which can produce common mode current issues and RFI emissions FROM the cable), I presume there is SOME vulnerability to RFI from amateur radio transmissions coupling INTO the ethernet cable that ferrites/filters can help with.  Gary, NA6O's comment backs this up with ferrite recommendations that seem to be based on his own experience, and it would be very instructive to hear more regarding when he found chokes to be needed (and why) and in what level of ethernet (10/100/1G, etc.).

I've just reviewed Jim Brown's (KY9C) very good writeup on RFI and ferrites, which includes ethernet RFI protection.  On Page 14 he makes the observation that unshielded, unbalanced home AC wiring can easily be the primary contributor to RFI entering the ethernet link via the power line into ethernet driven devices and discusses use of an AC line isolation transformer later in the text to prevent this.  Exactly what solved the problem with my son's game console.

Regarding:

Quote
The commercial RFI devices are overpriced….

Perhaps, but $50 is not too bad for a pair of nicely packaged, easily moved line filters.  The mix 31 toroids are about $10 each, with two needed to be comparable to the DXE kit, plus a new, longer ethernet cable (ballparked at $10) to absorb the 15 turns needed at each end (30 total).  So its a difference of $20 per line, not $40, to have a pair of clean, movable filters vs. a pair of hand wound, bare (and conductive) mix 31 toroids that are fixed to one cable.

While I agree that in a very thorough treatment, each and every line into and out of a router or switch will need to be filtered - and that would also multiply  the cost differential - it's probably also overkill.  I'd do it for a commercial installation, but would experiment more for a lower budget ham application.  Consider that a simple router/switch will have at least 6 lines to be protected, 4 of which, in the best case, will need two rather than one filter.  Thats going to run more than $150 even with hand wound toroids.

Very possibly it's simpler and cheaper to get the easy, drop-in filters, and just move them around to see which lines they're most effective on rather than"shotgunning" all of the lines at once.

And per Jim Brown's writeup, spend some of the savings on mix 31 chokes or an AC line isolator (about $120 on Amazon) for the game console power lines.

Again, just some thoughts.

Brian - K6BRN

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WA3SKN

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Re: Getting RFI out of Spectrum Wired / wireless router.
« Reply #7 on: August 03, 2022, 12:51:18 PM »

OK, 40 meter RF is overloading SOMETHING!
Is it incoming via the power lead?
Is it incoming via the CAT5 cable?
Is it the router?
Maybe... ALL the above!
And maybe you could move the 40 meter antenna farther away from the eqpt.

The power lead is easily filtered with capacitors, inductors, ferrites, and aluminum tape.
You can shield the router with aluminum foil... BUT the "wireless" 2.4 and 5.6GHz signals don't get out.  Are you using them for other things? (always!).
And you can use ferrites on the CAT 5 cables and/or... they DO make SHIELDED CAT5 cables... they just cost more. And you CAN use aluminum tape to shield those CAT5 cables too!  Ground the shield at only one end.
So how long are the cable runs?  And remember when routers were made with METAL cases?

If you shield the router, remember to let air circulate.  You can use metal screening instead of foil.

-Mike.
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N6YWU

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Re: Getting RFI out of Spectrum Wired / wireless router.
« Reply #8 on: August 24, 2022, 07:10:02 PM »

Yet more options (perhaps expensive) to deal with a problem router with EMI or RFI issues might be to put it in a metal box with a power isolation transformer plus toroids on the power cord, then add an external but less-RF-noisy WiFi router outside the box.  Then replace all long run ethernet cables with media converters at each end and use fiber optic cabling (multi-mode or single mode, depending on distance) in between.  Leaving no metal to conduct EMI out from or RFI into the problem router.
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AI5BC

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Re: Getting RFI out of Spectrum Wired / wireless router.
« Reply #9 on: August 26, 2022, 08:36:49 AM »

Follow electrical codes and you will not have the problem. Bring your coax inside where your CATV and Electric Service enter using the same ground point.
Sounds like you did what most hams do, shoot yourself in the foot and take the coax directly to your room or shack. Guaranteed to have RFI problems. That is why ham shops sell ferrite products, to make money off all the mistakes. Your radio is using the modem wiring as an antenna. Follow codes and you eliminate most problems.
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WA3SKN

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Re: Getting RFI out of Spectrum Wired / wireless router.
« Reply #10 on: August 28, 2022, 08:58:33 AM »

I find it much more cost effective to determine how the RFI is getting into the system and then filtering, as opposed to just randomly filtering until the problem disappears by magic.
However... "distance (tx antenna to rx antenna), filtering, and shielding", are always the answer to interference issues.

-Mike.

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K6BRN

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Re: Getting RFI out of Spectrum Wired / wireless router.
« Reply #11 on: August 28, 2022, 01:13:09 PM »



See September 2022 QST, page 49, regarding the use and effectiveness of the DX Engineering ISO-PLUS Ethernet line filters.  Apparently they work quite well, but do not allow DC-pass through.  Not just simple ferrite chokes.

Brian - K6BRN
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W9IQ

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Re: Getting RFI out of Spectrum Wired / wireless router.
« Reply #12 on: August 28, 2022, 02:06:20 PM »



See September 2022 QST, page 49, regarding the use and effectiveness of the DX Engineering ISO-PLUS Ethernet line filters.  Apparently they work quite well, but do not allow DC-pass through.  Not just simple ferrite chokes.

Brian - K6BRN

That is correct - do not put them on a POE line unless you are prepared to add another power injector. Of course that is ironic as often the injector is a source or conveyor of RFI.

- Glenn W9IQ
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

KL7CW

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Re: Getting RFI out of Spectrum Wired / wireless router.
« Reply #13 on: September 08, 2022, 04:31:21 PM »

I had a problem with my 250 foot run of 5e ethernet cable from my rx array 250 feet from the shack.  It was common mode pick up of RFI from various sources traveling out to the RX array, or possibly back into the shack.  I used 3 type 31 cores (2.4 inch) to solve this problem.  One core in the shack, one about 50 feet away outside the house, and a final one perhaps 20 feet from the array.  Each core was very effective reducing some signals 2 or more S units on 160 through 40 meters.  I used perhaps 25 RJ-45 connectors at various places, so it was easy to just insert a core and see if it helped. A second core at one location seldom helped, but a core out near the other end did help.  I think the cores used ABOUT 14 to 15 turns, and one used a special 5e cable which was flat, but they all worked about the same from BC band up to at least 40 meters. AC line filtering is also a good idea.  Also I made some mistakes in my array.  I should have isolated the DC + and DC - supply line, within the 5e, although perhaps I was lucky.  All unused pairs were terminated with I think 110 ohm resistors at each end.  Not sure shielded cable would be better or worse.
    Not sure if this helps in your situation.  Be sure to threshold the RFI from your 40 meter TX each step you take.
For example if it takes 40 watts to cause problems, then see how much power is required to cause problems after one fix.  Say it takes 100 watts.  Great, step one helped.  Go to step 2, etc. etc.,   You need to know what helps, or even occasionally makes the problem worse.  You could also do some research and see if the type A pin out or the type B is better in your situation.  Usually either works, especially for a short cable run, just be sure each cable has A on both ends, or B on each ends.  RJ 45 crimp connectors are very easy to install, especially after you practice on about 10 of them.  Buy a cheap tester (probably less than $20 at a box store) and crimper.  Never again will I try to troubleshoot cables by sticking pins in the ends of connectors. Another obvious easy step is just try another ethernet cable.  Not all prefab RJ and RG cables are reliable, and some techs prefer to make their own, at least that is what some did in the shop I worked in.             Rick  KL7CW
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G4AON

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Re: Getting RFI out of Spectrum Wired / wireless router.
« Reply #14 on: September 11, 2022, 01:57:34 AM »

OK, 40 meter RF is overloading SOMETHING!
Is it incoming via the power lead?
Is it incoming via the CAT5 cable?
Is it the router?
Maybe... ALL the above!
And maybe you could move the 40 meter antenna farther away from the eqpt.

-Mike.
That is the problem, trying to guess where the RF is being picked up is a frustrating and time consuming business.

Checking cables for RF pickup is easy and cheap to do. A common mode clamp meter can be made in a spare hour using parts that many of us have in the junk box. In my case a spare coax feeder connected to an antenna switch was carrying significant RF on the braid/shield causing RF current to flow on cables in the shack… who would have suspected that?

A simple common mode current meter is described on this web page: http://www.ifwtech.co.uk/g3sek/clamp-on/clamp-on.htm

73 Dave
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