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Thread: power supplies with minimal radio interferance?

  1. #271
    Raw Wave
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    The chassis & body of a car can also act as a Faraday cage.
    But if it is an antenna and hence picking up noise, that GND noise will be common noise and hence have no effect.
    STUDENTS - please discuss the above statements.

    You might have GND (loop) issues but that should be due to other reasons (dc paths etc).

    But I'll let Mickz handle this discussion. He way outranks me, AND he's an Aussie.

  2. #272
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    I understand. cm these are the photos of the homes of the M4







    the feedthrough capacitors, are welded on a base of copper, which in turn is linked to the whole metal box.

  3. #273
    Maximum Bitrate Mickz's Avatar
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    Nice work with the construction of the case. My only concern is the painted covers.

    1. Are they aluminium?

    2. Has the black finish been removed on the inside of the covers where they attach AND mate to the aluminium chassis?

    As far as the vehicle chassis is concerned, OldSpark suggested a possible ground loop and it is likely a variation of this.

    You are dealing with spurious RF noise. The vehicle chassis is a VERY POOR conductor at RF frequencies. RF interference voltages will develop across even 2 inches of vehicles steel chassis.

    The level of interference from a PC MB (Mother board) can kill a GPS, and it varies with the brand and model of MB. I recently traced a problem for someone that was caused by the refresh rate of the GPU. At 59 Hz there was no interference, at 60Hz or higher the GPS stopped working. Connections were via High quality HDMI.

    The problems with a PC MB and the various clock frequencies on the MB and external components is the Harmonic interference generated by nonlinear mixing of these various RF sources. Some of these sharp rise time clock sources are unstable, in the case of a PSU and/or PWM circuitry they can have constant changing duty cycle and frequency causing random shifting multiple spurious noise to be generated anywhere in the RF spectrum.

    In severe cases the PSU and MB should be mounted on a piece of aluminium to eliminate as much as possible the ground RF path resistance between them. At the very least a very short 4g cable from the aluminium chassis to the vehicle chassis and with 0g to 4g ground and supply cables directly from the battery terminal to the PSU with +12v fused near the battery.

    In some situations the PSU in its case and the PC in its case are both mounted inside a larger aluminium case to reduce RF radiation around the internal cases and the connection leads. The difference can be like night and day in some installations.

    Some have no problems with their installation, but it depends on so many subtle variations in components, layout, lead routing and type of receiving devices installed.
    Last edited by Mickz; 02-06-2014 at 08:50 PM.
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  4. #274
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    hello I'm redoing the case pc so you can install everything inside. that being the case I'm making the Pc of MDF, I could use the inside of the copper sheets in such a way as to shield the entire case pc? the box is made of sheet feeder (black part) the aluminum fronts.

  5. #275
    Maximum Bitrate Mickz's Avatar
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    Sheet aluminium will work just a well and is lower cost, but if you have copper then go for it. In my build I made a case with a hinged lid from ply, fully lined with sheet aluminium, covered with matching trunk carpet and mounted in a recess in the trunk floor.

    Not sure what sheet feeder is, but if its steel or tin then the effect of the feed-through caps and shielding could be compromised. The toroids on the M4 pass high currents and will close couple into the steel case, causing RF to bleed into the outer case, any lead in close proximity to or resting on the case could be contaminated with RF.

    Best of luck.
    GA-Z77N-WIFI, i5-2400S, 8GB, Intel 520 128GB SSD, M4-ATX Modified, 2 Rev Cams, 2 Web Cams
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    T-Screen HVAC control, custom microcontrollers, code and FE. CarPC Project

  6. #276
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    Since in this whole thread it has only been mentioned once or twice: Stop buying the Mx-ATX PSUs and buy quality like Opus or DSATX instead!
    It hurts my soul seeing people putting so much effort into trying to fix a crappy PSU, just to go from no reception to tolerable reception or trying to get rid of noise with dozens of solutions.
    Last edited by Gullimonster; 02-07-2014 at 06:26 PM.

  7. #277
    Maximum Bitrate Mickz's Avatar
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    1: Yet people on here have complained of interference and problems with the Opus in some installations. Yes the M4 is noisy - but:

    2. The Opus was 3 times the price over here when I purchased the M4.

    3. It only needed shielding for DAB, sometimes GPS - depending on where GPS is mounted.

    4. Mine is now years old and has preformed faultlessly since the interference was solved.

    5. That does not solve the problem for someone who has already purchased one, hence this thread.

    6. If someone had READ this thread BEFORE purchasing an M4 then they may NOT have done so!!!!

    And yes, I'm sure we all should of researched every item of purchase like everyone else in the world had done.
    GA-Z77N-WIFI, i5-2400S, 8GB, Intel 520 128GB SSD, M4-ATX Modified, 2 Rev Cams, 2 Web Cams
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  8. #278
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    Quote Originally Posted by Mickz View Post
    Sheet aluminium will work just a well and is lower cost, but if you have copper then go for it. In my build I made a case with a hinged lid from ply, fully lined with sheet aluminium, covered with matching trunk carpet and mounted in a recess in the trunk floor.

    Not sure what sheet feeder is, but if its steel or tin then the effect of the feed-through caps and shielding could be compromised. The toroids on the M4 pass high currents and will close couple into the steel case, causing RF to bleed into the outer case, any lead in close proximity to or resting on the case could be contaminated with RF.

    Best of luck.
    What do you think of the graphite spray?

  9. #279
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    I personally dont have experience with the Opus, but as I said, the DSATX is there too, and I have experiences with it. Its flawless and extremely sturdy.
    For a car PC you should actually do some research on such components. And as I also said, I am only mentioning it because it hasnt been mentioned here except like 1 or 2 times on the first few pages. So maybe it will save some people a lot of hassle, if it is being mentioned again after so many years, since its completely on topic in a thread that is named "power supplies with minimal radio interferance?".
    Sorry if I hurt your ego in any way with my comment, I just wanted to help.

  10. #280
    Maximum Bitrate Mickz's Avatar
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    I think you misunderstood the reply, I was trying to be civil and not did get into silly personal comments like ego.

    Thanks for your helpful input and insight to this thread.

    There will be no further response from me to your posts.
    GA-Z77N-WIFI, i5-2400S, 8GB, Intel 520 128GB SSD, M4-ATX Modified, 2 Rev Cams, 2 Web Cams
    8" 16:9 TRANSFLECTIVE, Win8-64, Dual GPS RX and Garmin PC + Odyssey Nav, FM-DAB+, BB-Rec
    T-Screen HVAC control, custom microcontrollers, code and FE. CarPC Project

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