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Thread: M4-ATX and Radio issues

  1. #1
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    Apr 2012
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    M4-ATX and Radio issues

    Looking for some advise from the pros.

    My M4-ATX has worked well, but I've recently added a DAB/FM radio, http://www.monkeyboard.org/products/...elopment-board, and the reception in the car is cr.. (both FM and DAB)

    Connected the radio to a laptop in the car, with the CarPC off, and reception is good. (Signal strengh in the 80-90%). Driving around town and all appears good with no dropouts on DAB.

    When I turn on the CarPC with the M4-ATX, the signal strength goes to somewhere between 0 and 20 with frequent dropouts. Btw, the radio is still connected to laptop at this point. Tried moving the CarPC to the boot, with the antenna sucked to the front window. (max distance between the two) No help. Still horrible reception even when parked in drive way.


    Based on some googling and these forums, I suspect the issue is the M4-ATX generating a lot of noise and killing the radio signal.

    1) Is it safe to assume the issue is the M4-ATX and to fix the issue I need to replace it?
    2) Assuming it is the M4-ATX, what DC-DC PSU should I get to avoid interference with radio? (and any other issues. The MP3Car store appears to sell alot of the M2, M3 and M4s, but...). Is http://store.mp3car.com/Intelligent_..._p/pwr-034.htm good enough?


    JJ

  2. #2
    Maximum Bitrate Mickz's Avatar
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    Sep 2009
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    Australia
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    Hi JJ, I posted this on the other thread but thought I would post here as well for anyone searching for M4 interference. The M4 is the main culprit, PC can be generate some but to a lesser degree and finally any device with an SMPS, such as a (some) cameras. It's a pain to have to go the expense and hassle of fitting the PSU into a correctly RF screened case, and even then placement and lead dressing around the PC are still important.

    It's not going to be easy to find a PSU that is (truly) free from radiated interference. You really need to find four or more people with PSU brand X that are running DAB-FM and GPS and have tested reception using a laptop (PSU on and off) out of the metropolitan area where reception is not saturated with DAB-FM signal levels. I have seen people fluke an installation with an M4 and have no reception issues in their location. I have technically proved beyond any doubt that the M4 is a noise generator, but so too are most SMP supplies, it just comes down to how much they produce.

    As others said, an external roof mounted aerial helps as it did in mine, but won't solve the problem when signal levels start to drop.

    Like I mentioned before, a tiny 1/4" x 1/4" SMPS in a camera completely killed DAB in my vehicle and no amount of simple ferrite beads, shielding or lead layout would fix it.
    Surface Pro 2 128GB portrait mode, Win8.1, Reverse camera, Dual 10HZ GPS RX's for Speed Display & Sat Nav, FM-DAB & Phone Modules, iDrive interface. T-Screen HVAC control, custom microcontrollers, microcode and FE. Previous Car-PC Project

  3. #3
    Newbie
    Join Date
    Apr 2012
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    44
    Thanks for this Mickz,

    As per http://www.mp3car.com/power-supplies...erance-22.html, it is the M4-ATX and I'll probably need to build a cage for it


    JJ

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