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Flex 6400 lockup ...


Have a look at my QRZ page for my setup ... quicker than having to explain the entire setup :-)

Flex 6400 + SPE 1.3K FA amp, remote controlled using SmartSDR 2.6.2 over a WAN for me (near San Diego) and a LAN (sharing with my host ham).

The problem - Remote Flex-6400 locks up at times while in TX and needs to be remotely rebooted. This is running with the amp at between 500W and 1.2kW. It does NOT lockup running the Flex by itself.

It's NOT the router, modem, amplifier, Raspberry PI 3, NUC, or interconnected cables as my TS-480SAT w/RemoteRig doesn't have any problem using the same amp, the same antennas at the same power levels. All are co-located in the same rack (picture on QRZ page).

As there is no analog ALC, the only cable entry points are the CAT 5 cable, the control line to the amp and the DC input.

I would like to read how others have resolved this issue. I plan to improve on the following:

  • Loop and add a RF choke to the CAT5 cable at the Flex connection point
  • Loop and add a RF choke to the CTRL cable (Flex to SPE amp) at the Flex entry point
  • Loop and add a RF choke to the DC input cable at the Flex entry point

The Flex is grounded to the same point as the amp and the TS-480 SAT

Anything I am missing?


  • KD0RC
    KD0RC Member, Super Elmer Moderator

    Hi Bruno, As a test, can you try operating without the Flex to SPE cable? That could narrow down the problem to that one cable.


    Len, KD0RC

  • Larry _ NY8T
    Larry _ NY8T Member ✭✭✭
    edited December 2020

    I have mix 31 snap-on ferrites on every cable connected to the flex.

    I live on a small city lot so some of my antennas are directly over the shack, this solved my problems, good to 1500 watts on all HF bands.

  • W4AFK Bruno
    W4AFK Bruno Member ✭✭

    Len - My TS480SAT + RemoteRig has no problems even with the amp at full power. They are in the same rack. This tells me that the RF is not affecting the router, modem, RemoteRig, Raspberry Pi (to remotely manage the amp) or the NUC (to remotely manage the Flex).

    I need to make sure I can use the Flex and the SPE without the control cable as I don't want to damage the amp or the radio. Note that I have a control cable from the TS480 to the SPE's port 2. Port 1 is for the Flex. As noted below, I have no issues with the TS480 and I am using the same type of control cable for both radios (the TS480 has an additional ALC line).

    My assumption - It's either coming in via the CAT5, DC or Control cable, which connect to the Flex. Those already have clamp-on chokes. We will loop the cables and add more chokes. By the way, CAT5 and Control cables are routed on the other side of the rack and as much as possible not in the same axis. This is only affecting the Flex 6400.

    Antennas: Not using any tuner as all are "tuned" with low VSWR (GAP, beam and the two "Horse Fence" inverted V antennas for 40 and 75m)


    Larry - Thanks ... that's what I thought. The beam is above the shack at 45 feet, the GAP is ~25 feet to the right, the two inverted Vs apexes are around 80 feet and 60 feet away. They do drape the rear of the shack so the Flex is definitely in the near field.

    We will add more chokes (I believe we are using Mix 31 now, but one on each cable near the radio) and report back :-)

  • Larry _ NY8T
    Larry _ NY8T Member ✭✭✭

    I share one bigger ID choke on cables that are close to each other, but get them as close to the radio as possible.

  • Pat_W5WTH
    Pat_W5WTH Member ✭✭

    I had a similar issue. For me, the LAN indicator on the rig would go from Green, to Yellow, to Red depending on how long my CW exchange was. On long exchanges the rig would disconnect. My max PWR is 100W, but turning the power down "fixed" it. The conclusion was RF getting into the LAN. Since your problem goes away on lower power, maybe it is the same issue.

    I snapped a few chokes in the LAN cable near the rig and a few on the coax maybe 15 feet from the rig and the problem went away.


  • W4AFK Bruno
    W4AFK Bruno Member ✭✭

    Follow-up - Solved the lock-up.

    • Moved the amplifier further away from the Flex-6400 in the rack (kept ~5U spaces between)
    • Moved the RF cables further away and as much as possible at right angles to any DC and control lines
    • Looped extra length cables and placed additional snap on chokes

    Now able to operate full power on all bands

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