Fixed my Ethernet RFI

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Sharing a rare event, successfully fixing a problem - Smile.

I have an ICOM 7300 sitting next to my new (to me) Flex 6500.  Setting up the new ham shack layout I discovered that the 6500 added 5-10 dB of HF noise to the 7300.  Closing the SmartSDR program stopped the noise, so I suspected the 20' Ethernet cable was radiating.  First I ordered a shielded Ethernet cable as a replacement, but several folks recommended against using it (concerns about grounding at the connectors?).  Instead of installing it I picked up some Palomar Engineers 1:1 Feed Line Chokes and put one on each end of the Ethernet with 3-4 turns. 

Result?  No detectable noise increase when the 6500/SmartSDR is up and running.   
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Steve - K6SRS

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Posted 4 months ago

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Rich McCabe

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Thats great.  Not sure what you meant with 3 to 4 turns but you want to avoid tight bends in Ethernet cable.  I typically buy snap on chokes 50 at a time and everything including Ethernet usually get two of them.  Sometimes more.  Regardless congrats on the fix Steve.

By the way the Flex was just talking to the 7300. Trying to teach it stuff :)
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Jim Gilliam

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Did you notice any change in the receiver noise in the 6500 with the chokes?
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David Ahrendts

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Or some of us do both -- CAT7 shielded and clamp-on ferrites. In my RFI hunt, one of the nosiest devices nearby was the D-Link switch. Shielded CAT7 solved that problem. 
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Stephen Hawkins NG0G

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Where is a good source of shielded cat7.  I have a firewall / router, and two 8 port switches and 11 computers all using cat5.  That is a lot of individual cables, in the shack and in a room in the basement under the shack..  I have the tools for putting on regular RJ45 connectors, do I need a different tool and different connectors?
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Craig Williams

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East coast. http://www.cablematters.com/
West Coast. https://www.cablewholesale.com/index.php
And, lots of vendors on eBay and Amazon.
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Jim Gilliam

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Did you use shielded cables on cable from the router and cables going to the devices?


Jim, K6QE

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Tim - W4TME, Customer Experience Manager

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The issue with STP (shielded twisted pair) is that both ends of the cable can make a ground connection to the chassis. Depending on how your network hardware is installed, it can create a ground loop and make the noise worse.  Unless you are running in a properly grounded data center or telco switch room, you can be almost certain that the two devices connected with the STP cable will have different ground potentials and currents will flow.

One trick to do is cut off one end and replace it with a plastic connector and connect the metal connector end to the device that has the best ground; usually the radio.
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Gary - WB5ULK

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In the early days of gigabit ethernet, clamp-on ferrites were shipped with new equipment more often than not. Buy a 24 port switch, get 24 clamp-on ferrites. And this was with Major Manufacturers - the knock-off brands left you to your own devices.

It really did make a difference.
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Mark - WS7M

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A somewhat expensive solution to this problem is to go fiber.  Run fiber from some other point to a small fiber switch right behind your flex then a very short net cable into the flex.

It has other benefits like some additional ESD protection over the net cable.
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