Caseless - RF emissions

Discussion in 'Computer Cases, Power Supplies and Cooling' started by A_Tom, May 27, 2014.

  1. A_Tom

    A_Tom Member

    Messages:
    58
    We all know that computers have to meet some FCC guidelines for RF leakage, but what if you are running caseless. I have 4 computers in my office, and none of them is in a case. Three of them are very close to one another, so it doesn't seem to have any effect on the computers themselves. There are also health standards for RF exposure limits, and I'm not sure what they are, but my question is, is a caseless pc likely to put out enough RF to exceed applicable standards for RF exposure, whatever they are. I'm not concerned for myself, but I would like to know if it's consider safe before recommending it to anyone else.

    There are several reasons I run them this way:
    1) They run cooler
    2) Fewer fans means they are quieter
    3) Dust is a non problem
    4) Repairs or replacement of components is extremely easy
    5) I can situate the computers to make the cable connections more accessible.
     
  2. Geoff

    Geoff VIP Member

    Messages:
    37,673
    To answer your first question, there are a lot more sources of RF to be worried about. PC's themselves don't intentionally transmit RF, and when they do it's minimal compared to an RF transmitter such as a cell tower, broadcast station, or even a microwave oven. I don't believe cases are designed to protect against RF, especially since many have windows and have tons of openings for fans and ventilation. I don't see it being a problem.

    Now to a few of your points.

    1.) I would beg to differ they run cooler, unless you have some other sort of air flow over the components. Having them sitting in a still room without circulation is worse than a case, which is designed to take air in from the front, move over all the components, and then get exhausted out the back and top. Without any fans, any passive cooling (just heatsinks without fans), commonly found on chipsets, memory, hard drives, etc., have no way of dissipating the heat.

    2.) Yes that's true, but then again a case also silences fans from the CPU and GPU, which without a case are louder.

    3.) I'll take your word for this, but even in a clean house dust accumulates fast, especially with pets.

    4.) The chance of repairs is greater due to a greater risk of static discharge, spills, etc. There is nothing protecting the components.

    5.) I'm not really sure how this is easier without a case. With a case, you route all the cables behind the motherboard so they are out of the way, without a case, cables are going every which way.
     
    Last edited: May 27, 2014
  3. A_Tom

    A_Tom Member

    Messages:
    58
    Thanks for the comments. I agree with your comments about the RF, but I'm looking for an authoritative source that I can point to if someone challenges my recommendation.

    Some feed back on your other thoughts as well.

    1 and 2. The mobo's are all vertical so they get convective and radiant cooling as well. I have no graphics cards, so the only component that requires active cooling is the cpu, and those fans are all in place and working. I cannot hear them, but I could hear the case fans easily. No matter how much air you run through the box, the ambient air temperature inside it is going to be above room temperature, which means the cpu must be running hotter than with no case. Other components apparently do not require active cooling, and since I've been running this way for years, it's apparently not an issue.

    3. The only thing which collects any dust is the cpu fan and cooler, which is due to the forced air circulation. And since they are readily accessible, blowing the dust off is a trivial matter. There is zero dust on everything else, except the power supply, which has the same problem of dust collection due to air flow and static charge. Again, these are very easy to clean because they are always accessible.

    4. There is virtually no chance of anything falling on these units and I've never had to do any repairs because of an accident, and they are very reliable.

    5. I was referring to the external cabling. When you have a case, the external connections are always in the back. If your desk is next to a wall, or you put the case under the desk, then changing a cable or connection is a problem. The internal cabling is just hanging there, but causes me no problems.

    Here's a picture of one.
    [​IMG]
     
  4. Geoff

    Geoff VIP Member

    Messages:
    37,673
    I don't have any reference material proving that about RF, unfortunately.

    Just a few more comments. Yes, the temp inside the case even with airflow will be hotter than the ambient temp. However, if you were to take a laser reading of various components I'd guarantee that the components themselves would be hotter without a case. If you have airflow in your room that's one thing, but if the air is pretty stagnant then the air immediately surrounding the components will remain much hotter than the air a few feet away. How often do you need to change connections on the back of your PC? With a case, most have USB, audio, and power connections on the top or front for easy access.

    How do you turn your computer on?
     
  5. A_Tom

    A_Tom Member

    Messages:
    58
    It would be hard to answer the temperature question without doing actual testing, but for the thing that matters most (the cpu), it's getting the benefit of cooler room temperature air, and that is good enough for me. And, as I said, I have a long experience factor with no problems, and I have 4 of them. And, yes, modern cases have most of the needed ports on the front, but it doesn't get any easier than having them all on the front.

    I use a momentary switch, same as you.
     
  6. bomberboysk

    bomberboysk Active Member

    Messages:
    13,257
    Cases do provide some RF protection, and mostly are there to ensure FCC Part 15 compliance (even unintentional radiators like a PC). Even well designed enclosures can cause spurious emissions in excess of Part 15 operation though (big issue with microcontrollers, especially).

    That said, you are correct however and no computer/etc should be able to get you anywhere near the level of RF where exposure limits become a concern. Cell phones/etc are easily an order of magnitude higher than a few caseless computers. Any possible issues will fall solely under ensuring Part 15 operation. The only way you can ensure that you are operating within Part 15 guidelines is to test that field strength is within limits at the appropriate range(which is relatively expensive).
     
    Last edited: Jun 1, 2014
  7. Okedokey

    Okedokey Well-Known Member

    Messages:
    9,506
    Unless a case is a solid, metal box, it provides no RF protection whatsoever.
     
  8. bomberboysk

    bomberboysk Active Member

    Messages:
    13,257
    Entirely incorrect. Cases are (supposed to be) grounded to an earth ground through the power supply, which earths RF energy. However, even when not earthed, the computer case has the same effect as a faraday cage (frequency dependent, obviously).

    If you want further proof get yourself an RF FSM and remove the side panel from a computer and then replace it. A considerable difference will likely be noted.

    An older, yet still applicable, pdf from intel has some information on this topic:
    http://www.intel.com/design/pentiumii/applnots/24333402.pdf

    4.2 will have a small amount of information on chassis design, rest of the document has some good information behind it though.
     
    Last edited: Jun 1, 2014
  9. just a noob

    just a noob Well-Known Member

    Messages:
    5,721
    The only problem I ever had running without a case was interference with my old tube style tv. When the computer was on there was snow over the image.
     
  10. Okedokey

    Okedokey Well-Known Member

    Messages:
    9,506
    Incorrect. That would only apply in a seamless, no-gap case.
     

Share This Page