Looking for a router that is somewhat impervious to R.F. interference

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On 40 meters, my Flex 6700 and KPA-1500 amplifier was losing contact with the radio when I produced a carrier running over 125 watts.  A Palomar choke in the antenna line brought the power up to 700 watts before the radio would lose connection. I have shielded Cat 7 on the lines running from the Flex to the router and from the shack computer to the router. The Windows 7 computer, on which SmartSDR is running, has a big EMI filter I built in to the power cord.  I have Ferrite beads on all Ethernet lines where they connect to the router and the computer. There is even a bead on the 12 VDC power cable to the router.  Strangely enough, the radio would be fine for a couple minutes before losing connection, however, as it ran, I could see the Flex network signal bars were going from 5 to 4, to 3 to red 2 to red 1 and then the connection loss would occur. Something appeared to be affecting the router's connection to the radio at higher power operation. I noticed that when using the 'office' computer on the same LAN to run SmartSDR, that I could operate the amplifier with a full 1,500 watts, with no connection problem. So I plugged the shack computer Ethernet line into the port that the office computer used and then I could run 1500 watts from the shack.

The router is a NetGear AC 1750 Dual Band (R6300 v1) that is about 6 years old. So, I'm thinking there is something funny with the port and the router is taking R.F. which is, seemingly, only affecting that port.  Now I want to solve that problem for good and would like some advice on buying a better router. It is unfortunate that we hams cannot find manufacturers specifications on how well their routers deal with nearby RF fields.  Can someone suggest a really good router that may do better? Looking for advice. Thanks.

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Doug K0DV

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Posted 3 months ago

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David Decoons wo2x, Elmer

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Doug I am using a Netgear Nighthawk R7000 with good success. Internet speed is 400 down x 35 up. Using same amp with a 6600 and no network dropouts due to RF. Antennas are G5RV for 40 & 80, 30 meter dipole, and Mosley TA-53M 5 band Yagi. 

G5RV is about 30 feet from shack (shack on 2nd floor of a bi-level house). Yagi on roof.

Are both the Flex and radio connected to the router? Any way to try cat 5 in place of CAT 7? 

Dave wo2x

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George Molnar, KF2T, Elmer

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Hi Doug,

First thing I would do is double check your radio installation. There could (probably is) some sort of a ground loop in play. Sometimes shielded CAT can be worse than "just" twisted-pair, too. Try a UTP CAT cable.

If it turns out to be a router problem, after all, I have had good luck with a Synology router. It has some extra features (like NAS, VPN, etc) that are very handy. Whatever router you choose, throw away the supplied switching-style wall wart supply and replace it with an analog power supply. Choke as much of the power lead as you can. 

K9YC and KY6LA have posted some extremely good advice on noise mitigation and overall system considerations; I recommend their work wholeheartedly.
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Michael Walker, Employee

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Doug

Do you have any chokes on your DSL or Cable from your ISP?

Mike
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Jeff, W4DD

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How is the router connected to the internet? DSL modem, cable modem, or something else? Most routers are powered by wall warts so typically have no good ground connection and no good way to get rid of RF. Since cable modems usually have a reasonably good ground via the RG6 cable, I ran a 3ft shielded ethernet cable berween the cable modem and the router. On my router (an Asus), the neg DC, ant connectors, and rj45 shells are all tied together, but were floating, no ground connection. Don't use shielded cables off of the common sites. The drain wires are not soldered to the rj45 shell and are intermittent. I used amphenol csbles from Mouser.
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Fred Friedl

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I have the exact same router for nearly the same time and routinely run legal limit on all bands and have never had the slightest issue.  I agree with KF2T idea of a ground loop.  Sometimes less is better than more.
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Doug K0DV

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Thank you all for your responses. I'll try response to all at once.

Dave, both the Flex radio and computer are connected directly to the router.  Thanks for the Nighthawk suggestion, that looks like a nice router.

George, I guess I was mistaken in thinking that shielded cat would help,  Seems to me the ground shield should be connected at one end to a ground. I can easily replace that run. Also, thanks for the suggestion of the Synology router.  I'll look into that. My experience has been that the routers themselves can produce all kind of unwanted R.F. emissions.  My 15 meters still has panadapter interference bumps and it may be from a switching supply.  I do have a special wall wart with extra filtering build in. I think it produces the same voltage output.  I replaced my shack's computer's power supply when it stopped working with a generic unit that was said to run my Dell model, but it had so much switching supply garbage on all the ham bands that I had to add a big EMI filter and that tamed it. Thanks for the other tips.

Mike, the cable modem is fed by fiber to its location in the basement.  From there an Ethernet line runs about 10 feet to the router. There is a ferrite bead on each end. (The 40 meter feed line also runs through that room.)

Jeff, as I told Mike, the cable modem is connected directly by fiber. It's a good 100 MByte service.  The Amphenol cables sound like a good choice.

Fred, ground loops can be nasty, particularly in audio. 

To all, remember I could do away with the problem by using a different router port, with the 'same' cable that was first used and displayed the problem. So, I believe that would point to an issue inside the router for that port.  I don't have a schematic for the router, but one could believe that it was improperly wired during manufacture and perhaps missing a capacitor filter ... or something.  But the suggestions about keeping the RF out of the router's Ethernet lines and power supply are all good.




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Gary - WB5ULK

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Doug,

Clamp-on ferrite beads are your best friend. Not only to they choke-off RF coming TO your router from your antenna, they also will keep router-generated RF from getting any distance FROM your router.

I have a full-wave loop on 80 fed by open-wire line just on the other side of a brick wall from my radio and router. Clamp-on ferrites cleaned it up.

Now YOU are going to ask "how many?" And my answer is this: you can never have too many clamp-on ferrite beads. 

But..

Put at least one on each and every network cable attached to your router, and if you still have issues, add more. The problem is almost always radiation from the cables, not from the router itself. But, you *can* by a really inexpensive router that may turn out to be the plague of the neighborhood. The recommendations up the thread are very good.

But use those beads!

Gary, WB5ULK
Ham, and retired Network Professional
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Doug K0DV

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Thanks Gary, all good suggestions. There are other suggestions to buy beads with 3/4" and loop the wire through as many times as possible.
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Gary - WB5ULK

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In the middle-era of ethernet switches, they were notoriously noisy - yes, even Cisco, and so the vendors typically shipped new switches (we were buying 48 port switches at the time) with a bag of clamp-on ferrites which would fit the larger ethernet cables (still used today). We did not experience the RF issues which others had, so I had drawers-full of these. One particular Cox Cable Modem I had was awful w/r/t noise susceptibility, and I started putting them the network cable stacked one after the other until the noise stopped being an issue. The price was right and it worked. The rest of the advice which you are getting is very good as well. What works "for you" is the best solution!
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EA4GLI - 8P9EH - Salvador

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In my experience it tends to be the power supply of the router and not the router itself. Try with a different psu for the router, or if you are lucky and it runs on 12v use your station power supply.
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Doug K0DV

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Salvador, my Netgear router uses a 2.5 amp 12 VDC supply.  I'll look into a amateur power supply that is not a switching supply or if it is it has more filtering. Can't use station 12 VDC as its too far away.
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Craig - KØCF

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A single bead may not do much. I use snap-on beads with a 3/4" diameter center hole. You can put 6 or 7 turns of CAT6 cable through it. This is highly effective. They are available from a number of sources, but they are not cheap. However, worth every penny because they work so well.

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Lasse Moell

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Good advice! As the impedance increases with square(number of turns), even 2 turns through the core will have 4 times higher impedance. I highly recommend FairRite -31 material, especially the "Big Clamp"  FairRite 0431177081. Drawback is its weight 300 gram each!   GM3SEK (writer of: In Practice,  RadCom RSGB magazine) has named this core "The Problem Solver"  Using this clamp on all my feeders and cables (core can take 4 turns of RG213), has not only removed all problems with RF getting into stuff,f it also has reduced the noise level on receive! That is a double bonus!!
Living across the pond shipping several kg of ferrite can be very costly so I usually buy from Arrow when they do offer free shipping! They often have good prices of the FairRite stuff too.
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Lasse Moell

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For those who are seeking more information I reccomend the following:
http://www.ifwtech.co.uk/g3sek/in-prac/

K9YC http://audiosystemsgroup.com/RFI-Ham.pdf

Should give you a good start.
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Doug K0DV

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Lasse, good suggestions.  Two of my leads connecting to the router have the wire run through the bead a couple of times, but the beads I had for the other lines will only accept a straight through run. I have looked at the FairRite you suggested, the problem is it's size and bulk and the shelf on which the router and switch is located will not handle them conveniently.  But, I have placed that core in my notes for future use.  Thanks.
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Doug K0DV

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Craig, I have beads of varying core #, most unmarked, picked up at ham fests. I think I need to purchase better cores and get rid of those cores that are truly junk.
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Lasse Moell

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Doug, it's not just the size but material that is important. The type I suggested do work with RG-213, but you can find smaller sized ferrite of -31 material that will work with CAT cables.  I do recommend you use ferrites not only on your TCP/IP cables but on DC-cables to your router, on mains and coax cables. Just make sure you do use the correct ferrit material -31 (or 43 may work).
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Michael N3LI

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I had two netgear routers that would reboot when I used 40 meters. I ended up using good ethernet cables, 2 inch toroids, on the cables,  and bought an Arris Router that had a metal case.
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Doug K0DV

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I have a small 8 port switch that the router feeds.  It has a metal cabinet.  Tried grounding the chassis once and it made thing much worse, probably formed a ground loop somewhere in the system.  The switch remains un-grounded.
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Larry Benoit

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Hi Doug:

I'm also inclined to suspect that the EMI is entering through your Ethernet cables and not directly into your router.

One simple thing I would test to narrow the diagnosis: disconnect all Ethernet cables (including the connection to your ISP modem), except the connection to your Flex radio and operate the radio with a laptop/tablet over Wifi.  If the problem persists, try improving the filtering on the radio's Ethernet cable. If the problem is temporarily solved, proceed to reconnect the Ethernet cables one at a time, starting with the ISP modem, until the problem reoccurs. 

DX Engineering offers an Ethernet filter set (discussed elsewhere on this forum), which reportedly works well, though I've never used them:
https://www.dxengineering.com/parts/dxe-iso-plus-2

Alternatively, for about double the price, you could try Ethernet to fiber media converters, which provide RF isolation between your router and radio and/or your computer and the router. I've installed these:
https://www.amazon.com/Gigabit-Ethernet-Converter-1000Base-LX-1000Base-Tx/dp/B06XZ6CV6W/ref=sr_1_4?keywords=fiber+to+ethernet+converter&qid=1561114303&s=gateway&sr=8-4
They are plug and play -- no drivers or software.

The offending EMI/RFI may be radiating from the shield of your feed line as evidenced by the improvement you saw with the Palomar choke. However, if your equipment is close to the 40 meter antenna, the source may be near-field radiation at higher power. 

Is the Palomar choke the type with inline ferrite beads or a Palomar wound toroid, one-to-one unun/balun?  A strategically placed one-to-one unun/balun designed with higher choking impedance on 40 meters may be more effective than the ferrite bead choke. 

Good luck and 73,
Larry KB1VFU





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Doug K0DV

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Larry, I have beads on all the Ethernet lines running to the router and it's associated switch.  I have tried to disconnect one Ethernet line at a time to determine if it was native to a specific wire run, and I saw the radio connection drop no matter which line was disconnected.  I suppose disconnecting all except one would tell me that a remain line was causing the issue, but I did not do it that way.   The choke is the Palomar current unun, 1:1, 1.5KW - SO-239 In/Out. Its a toroid. It worked very well, but did not completely cure the problem. I have looked at the DX-iso-plus 2 Ethernet filters and for the convenience, I may very well replace the beads I'm using with those units.  Thanks for the tips.

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Larry Benoit

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Hi Doug,

You noted in your original post that when you connected the shack computer's Ethernet cable to the router port occupied by office computer's Ethernet cable all was well at 1500 watts output. If I understand this correctly, did you also connect the office computer's Ethernet cable to the router port previously occupied by the shack computer's Ethernet cable -- thereby swapping the router ports?  Did the office computer also suffer disconnections from the radio after the cables were swapped?

73,
Larry KB1VFU
  


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wa4wab

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 I would look at some of the mid to high end Linksys routers (owned by Cisco). 
You could go to Walmart and get a new one to try and if it doesn't solve the problem take it back.