Quiet PC Monitor

Discussion in 'EMC Matters' started by Mark Owen, Mar 23, 2017.

  1. Mark Owen

    Mark Owen New Member

    Hello all wonder if anyone here knows of a quiet 22inch PC Monitor as my old one has become noisy on HF and there's enough QRM from neighbours property's with out me adding to it. Any advice on a Radio friendly monitor would be most appreciated Thanks es 73's
  2. Peter Torry

    Peter Torry New Member

    Hi Mark,

    I have been using monitors from AOC for some time without any issues. They have a range of sizes and they perform rather well.

    73
    Peter
    G3SMT
  3. Martin G0HDB

    Martin G0HDB New Member

    Hi Mark, I've currently got a Dell 2007WFP (20") and a Dell U2412M (24") in use with the two PCs (one for radio-related stuff and one for home-office stuff) in my study-cum-shack and I've never detected any RFI from either of them. I only recently got the (second-hand) 2007WFP, it replaced a Dell 19" monitor I'd used for quite a few years with the 'radio' PC and I never noticed any RFI from that monitor either. I definitely don't detect any difference in the noise floor on the various HF bands between the monitors being on or off - there's more than enough external crud on the bands these days anyway... :-(

    Hope that helps,

    --
    Martin G0HDB
  4. Ken G3SDW

    Ken G3SDW Moderator

    Hi Guys, thanks for your input which is helpful to Mark.

    As for me personally then i can recommend all the Samsung range which are completely RF quiet.

    73

    Ken
    G3SDW
    EMC Help Desk
    RSGB
  5. Mark Owen

    Mark Owen New Member

    Thanks for your help gents 73's
  6. Ken G3SDW

    Ken G3SDW Moderator

    Not a problem Mark, let us know what you decide to get and how you get on.

    Always here to help at any time at all

    73

    Ken
    G3SDW
    EMC Help Desk.
  7. Mark Owen

    Mark Owen New Member

    Hi all sorry for not getting back to this thread sooner, im still in the process of getting a new monitor i am wating for a reliative to replace there samsung monitors. I want to try them before buying a new monitor.
  8. Ken G3SDW

    Ken G3SDW Moderator

    OK Mark well if you get any problems then I will eat my hat lol.
  9. Mark Owen

    Mark Owen New Member

    Just a quick update i bought a Samsung Pc Monitor this model from Argos
    Samsung S22F352 22 Inch LED Monitor http://www.argos.co.uk/product/531893and i have to report that this model is noisy. I am guessing its the rather cheap feeling SMPU used to power it, its puting an exstra 3 S points on my S meter on 40mtrs so it will be going back.
  10. Ken G3SDW

    Ken G3SDW Moderator

  11. Carl G3XGK

    Carl G3XGK New Member

    Hi Mark


    I have a BENQ XL2411T this is also vy noisy on the upper HF end, bad on 28MHz has S9 digital noise every 100+kHz when there is a video display. I think it is the LED back light SMPS. I have tried an inline mains filter next to the mains inlet socket of the monitor together with a Fair rite ferrite block with 3 turns on the video interface and there is no difference. I think the noise must be radiated from the innards rather than conducted and radiated.


    GL in finding something, please let us all know when you do Mark.


    Hpe you put plenty of ketchup on ur hat Ken...


    Best regards

    73

    Carl G3XGK
  12. Ken G3SDW

    Ken G3SDW Moderator

    Well i have used both and without any problem at all.

    One thing that needs to be checked is the cable which is connected to the PC, it is very important to make sure that it has adequate screening, lots of cabkes just have one wire for the earth return, its worth investing in a double screened cable which are not very much more expensive.

    I say this as both makes mentioned both have good track records for radiated noise.
  13. Carl G3XGK

    Carl G3XGK New Member

    Hi Ken and Mark


    Interesting point regarding the video lead Ken.


    What I found with the BENQ XL2411T is that even with no video leads connected to the monitor there was a noise problem, i.e. no computer active.

    When the monitor powers on it displays the words “BENQ LED” with a reddish background and the noise on 28MHz rises abt 4 S points on the Icom IC7400 (around 15dB). This display then clears to black and the noise falls to around the normal background level, this makes me believe that it is probably radiated, rather than conducted and radiated. The only wire that is not filtered is the mains earth wire.


    I wonder if there really are any ‘good’ makes on block and maybe it is down to actual models themselves.


    Best regards

    73

    Carl G3XGK
  14. Ken G3SDW

    Ken G3SDW Moderator

    I get asked this one all the time and the two i recommend as 1. i have used them myself and 2. i get reports from other members confirming that they are quite, and these two makes come out on top.

    It seems as today it is the luck of the draw as these two are not good at all, but from what you have said Carl then for me your problem is conducted into the mains supply, so to prove it you need to fit a couple of decent ferrites have at least a couple of turns on each.
    Last edited: Dec 18, 2017
  15. Carl G3XGK

    Carl G3XGK New Member

    Hi Ken and Mark


    The mains is filtered by an inline inlet filter (hooded) that I have put in series with the monitor IEC plug. And hopefully by another one (?) internal to the Monitor itself ? But as I mentioned the earth wire is never filtered in these type of basic line filters.

    Inside these filters there is a capacitor across the line L&N, two chokes in each leg towards the load and two capacitors to earth on the Load side.

    So I guess if there is an unbalance in the load noise, i.e. more noise voltage on one leg, then this would force a noise current down the earth wire into the mains wiring, which would then probably radiate it.

    I have just tried a ferrite (Fair Rite clip on 0431173551 18.5mm 31grade 125ohms/T at 25MHz) on the mains lead as you suggested Ken.

    I managed to put three mains lead turns thro’ it. Giving around 500R at 30MHz hopefully.

    This made no difference at all. The noise increases by 4 S pints as before every 190KHz across 10M and abt 2-3 S points inbetween the peaks.

    So I can only assume it is radiated from the large monitor innards i.e. maybe a large metal screen inside or the LED inverter wiring. I have no manual to show this but that is what I have found inside Samsung units I have repaired in the past.

    Unless there is a fault that is causing this, but I have no idea what could do this Ken.


    Best regards

    73

    Carl G3XGK

    upload_2017-12-19_10-40-40.jpeg upload_2017-12-19_10-41-9.jpeg

    Attached Files:

  16. Ken G3SDW

    Ken G3SDW Moderator

  17. gm3sek

    gm3sek New Member

    Fair-Rite No.31 is the 'correct' ferrite material for best results, but 3 turns through a small bead may not be sufficient impedance to draw any firm conclusions about the interference pathway.

    That was why I recommended not only the Fair-Rite #31 material but specifically the LARGE clamp-on core (Fair-Rite Part No 0431177081) with 6-8 turns. It needs ALL THREE of those things to create a dependable, broadband high impedance resonance at HF.

    If someone skimps on even one of those three requirements, then (with the greatest respect) they haven't earned the right to say "I tried ferrite".

    73 from Ian GM3SEK

    PS: Written on a BENQ LED monitor.
    Ken G3SDW likes this.
  18. Ken G3SDW

    Ken G3SDW Moderator

    Thanks for replying Ian and agree with your words regarding Ferrites which in my estimation is a word used all to loosely these days.

    I regularly instruct member's to use you web page so as they can appreciate how important it is to use the correct product.

    Thanks for your input.
  19. Ken G3SDW

    Ken G3SDW Moderator

    Just as an addition to this post, i have today had to replace my old 22 inch Samsung monitor which i use for my CCTV system.

    It is another Samsung, 19inch model LS19F355 and can report that it is as quiet as a mouse.

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