[MLB-WIRELESS] Mitsu R100 (Asus 500g) causing interference

[Zik Saleeba]

I work at NEC where we're developing embedded computer systems which are
quite similar to wifi routers in a lot of ways. You wouldn't believe the
amount of effort we have to go to in making these things meet EMI/RFI
emissions standards. We spend months trying to shield out the crap which
modern processors radiate all over the frequency bands. Even something as
"simple" as USB is horrendous for emitting wide-band interference. USB
cables act as excellent antennas, it turns out.

Some chips emit a lot of EMI and others don't. It's very disheartening to
come up with a design, go through the multi-month prototyping and
fabrication process only to find out that one of the chips you chose just
happens to emit all sorts of crap and there's no way it'll ever meet
emissions standards. That's something they don't mention in the data sheets
let me tell you. Your only option then is to redesign with a different chip
and cross your fingers that you'll have better luck this time.

Switching power supplies are a classic generator of EMI so like other people
said the power adapter's a definite possibility. But I just wanted to point
out that making any modern high speed digital electronics RF-quiet is harder
than you might imagine!

Cheers,
Zik

On Wed, Dec 3, 2008 at 9:39 AM, Peter Buncle <peter at nmc.net.au> wrote:

>  I concur
>
> Peter
>
>
>
>  ------------------------------
> *From:* melbwireless-bounces at wireless.org.au [mailto:
> melbwireless-bounces at wireless.org.au] *On Behalf Of *Tyson Clugg
> *Sent:* Wednesday, 3 December 2008 12:15 AM
> *To:* emdeex
> *Cc:* melbwireless at melbournewireless.org.au
> *Subject:* Re: [MLB-WIRELESS] Mitsu R100 (Asus 500g) causing interference
>
> 2008/12/2 emdeex <emdeex at gmail.com>
>
>> I thought that as well, the interference would be waaay out of band...
>> but...
>>
>> Do you mean the AC/DC plugpack?  I've tried it with the plug pack
>> still powered up, the R100 unplugged, and there is no interference.
>> So it's the R100 unit causing the interference.  Something inside the
>> unit.
>
>
> Don't be so quick to jump to conclusions - it may be that the plug pack
> generates RF noise under load only.  You should try with another plug pack
> (of same voltage and same/higher amperage/wattage) before asserting the R100
> is at fault.  I would especially suspect the plug pack as most are low cost
> switchmode circuits which typically switch at frequencies that would cause
> interference on AM/FM radio.  You can also try to find another device of
> similar load to the R100 to power from the plug pack and see if the
> interference remains.
>
> Regards,
> Tyson.
>
>
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