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Rfi on moitor

Joseph Coffaro
Joseph Coffaro Member ✭✭
any one have any suggestions  or recommend a HDMI cable getting rfi on forty but no other band.


  • Mark NS9N
    Mark NS9N Member ✭✭
    edited March 2020
    Are you sure it is the cable and not the monitor or the power supply for the monitor? If you have isolated it to the HDMI cable there are shielded versions but very expensive. None of the cheap cables are even close. Or you can try a large ferrite and put a couple of loops on the HDMI cable through it.
  • Steven WA8Y
    Steven WA8Y Member ✭✭
    edited March 2020
    Try a clamp one ferrite or two at each end of the cable.
  • Neal_K3NC
    Neal_K3NC Member ✭✭
    edited March 2020
    What is the SWR of your antenna on 40? I suspect there is an issue there. You can beef up the HDMI cable but its a digital transfer and thats pretty immune to RFI (if it gets it, the data doesn't decode). So I think you have either a high swr problem on 40. You can also prove this by going into a dummy load and see if it happens (which I doubt it will). Also, if its hitting your monitor, its likely hitting other stuff in your house.
  • Sergey KN7K
    Sergey KN7K Member ✭✭✭
    edited March 2020
    I have 3 LCD monitor, all the same, one of the monitors going pretty frequently black when I TX with full power.
    It is nothing to do with SWR, I can tune my steppir to 1.02, ferrites on the power and mini DP port do not help.
    All 3 Dell monitors use the same mini DP cable with the same ferrites. 
    Did not find solution yet.

    Sergey, KN7K
  • Mark NS9N
    Mark NS9N Member ✭✭
    edited March 2020
    Just a suggestion if you have not done so already, switch the monitors and see if it follows the monitor. If not switch the cables between two of the monitors . Then the ports on the computer. Trying to identify the root cause using A to B swapping.
  • K0FLY
    K0FLY Member ✭✭✭
    edited March 2020
    Been there done that.  I purchased several of the largest Mix 31 clamp on cores (I think they have a 3/4 inch hole).  I ran three turns of the HDMI cable through them as well as a smaller clamp on for the power cord ( six turns) .  Problem cured.  I run ladder line into the shack and tune with a Johnson KW matchbox.  The ladder line runs about 2 feet from one of the monitors.   The monitors appear to be most susceptible  to 40 and 30 meter signals .  No problem on any of the other bands

    Gayle K0FLY
  • Patrick
    Patrick Member ✭✭✭
    edited June 2020
    How long is your ground run?  When thinking about and evaluating a problem, if your ground run is at let’s say ¼ wave length from (equipment ground point) the ground point (ground rod).  Then your station is at the high voltage point in the RF wave at the affecting frequency.  Solution is to change the length of the ground run.  I had an old station long ago that that was hot on 20,15 and 10 meters (harmonically related bands) that and was some 20 feet from the ground rod.  Solution on this problem was to hang ¼ wave radials from the station ground point out away from the house.  This moved the high voltage point away from the station.  Solved my hot equipment problem.  Another problem most recently encountered, was miscellaneous interference on other device (stereo, weather station etc.) that killed their operation.  Individual ferrite did not work as there was cross coupling in many places on the various interconnects.  So I built brute force filters to put on the power lines,  this worked 100% to stop the common mode RF on all devices connected.  All systems the station, amp and stereo all have these filters.  A side affect of this was a reduction of about 5 to 8 db in my Flex 6500 noise floor on almost all frequencies.  Evidently common mode RF from the power line, which includes stuff from wall worts and even the AM broadcast stations 6 miles away was being felt by the Flex via the power line.  I built my filters using both #75 and #31 ferrite donuts in metal junction boxes. This gave me an effective rejection from 150 kHz m to above 30 MHz with an overlap  from 1 MHz to 10 MHz.  These solutions may or may not be applicable to all your problems, but when thinking about RF interference problems one must always evaluate starting from the wave length point of view.

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