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RFI in the LAN Cable causing disconnect [solved]

Pat_W5WTH Member ✭✭
edited October 2020 in Networking

I had an issue were the network connection status bar would go RED when I did a normal 3x3 CW CQ on 20m and 30m. @Ken Wells said it was likely RF getting into my LAN cable and, of course, he was right. He gave a few suggestions. Since the problem went away with only a small power reduction I went the cheap $10 route [https://www.amazon.com/gp/product/B01E5E5IY4].

One 'bead' seemed to work fine (pic attached). What was interesting is if I clamped in a bunch of beads the rig would reboot on 30m Tx. Hmmmmm......

Thanks Flex support.

Pat / w5wth


  • Bob W8RMV
    Bob W8RMV Member ✭✭
    edited October 2020

    Can you describe how a ferrite on a LAN cable reduced the power output of the Flex?

    I have tried ferrites on LAN cables before & I was shocked at how much the speed (Mbps) was affected. They lowered the speed dramatically. But I dd not see any power loss at the coax to the antenna.

    PS- I was using Mix31 when I ran the LAN speed test.

    -Bob W8RMV

  • Jeff Schwartz
    Jeff Schwartz Member ✭✭

    FYI, I used two Ethernet RFI filteres from DX Engineering, one on the Flex end and one on the router end of the cable which took care of my disconnect issues at all power levels on all bands 6-160M. https://www.dxengineering.com/parts/dxe-iso-plus-2

    Jeff / KI0KB

  • Pat_W5WTH
    Pat_W5WTH Member ✭✭

    >Can you describe how a ferrite on a LAN cable reduced the power output of the Flex?

    Bob, it didn't...... When CW Tx'ing at 100W my LAN status meter in SSDR would go from green to yellow to red to disconnect (on long transmissions). Turning down the power from 100W to 70-80W made things better.

    I snapped the bead onto the LAN cable going into the back of the FLEX and that seems to corrected things. The bead on the LAN cable choked the (I think) common mode RFI out of the LAN cable. The RFI in the LAN cable was effecting the fidelity of the LAN connection into the Flex.

    pat / w5wth

  • KD0RC
    KD0RC Member, Super Elmer Moderator

    @W5WTH Hi Pat, if RF is getting in via the LAN cable, it may well be coming in on other cables as well (which may or may not cause issues on any given day). If you have more ferrite beads, you may want to put them on all cables (including ant cables) coming in to the radio. You may also want one on the cable from the wall to the modem/router in case that is the RF path. It is hard to say if the RFI is causing problems with the radio, the modem, or both so I tend to try to block all possible paths.


    Len, KD0RC

  • Pat_W5WTH
    Pat_W5WTH Member ✭✭

    Thx, @KD0RC !

  • John K3MA
    John K3MA Member ✭✭

    You could consider fixing other potential issues at the same time by converting your LAN feed to the Flex to Optical Fiber. This article might help you.


    If you want to go in that direction I have a few HP Procurve commercial multiport switches and Trendnet Media converters that I am not using and would sell a set for under $100. One of each of those with some inexpensive optical fiber cable between them would be all that is needed. Certainly much cheaper than sending your radio back to Flex to repair the LAN port.

    John K3MA

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