Spikes in the Ether – EMC and Compliance

RE: Spikes in the Ether – EMC and Compliance

e14 Contributor — Wed, 04 Apr 2012 18:48:52 GMT

I've got the same email, after all I registerd with both of RS and Farnell at the time, but if you read it, they actually say "when we'll have the certification released" as the first thing.

So no, not really a change, they're just taking time. Farnell just didn't say it ("we are still doing the compliance tests") but I guess it's what is going on.

And since, PeteL said, they were supposed to do them this monday, ... if for the end of the week there isn't info, like big fat post on RPi blog, I'll assume they didn't go well and there ae other issues to iron out. :|

RE: Spikes in the Ether – EMC and Compliance

e14 Contributor — Wed, 04 Apr 2012 15:10:15 GMT

Well.....it's been almost a week since the last update on compliance testing.

Any new news?

RE: Spikes in the Ether – EMC and Compliance

e14 Contributor — Fri, 30 Mar 2012 03:10:35 GMT

Pete,

Are you trying to meet the Class A industrial standard, or Class B residential?

If a particular HDMI cable is used for testing, will that cable need to be bundled with the RPi?

10db over the limit means the emissions are 10 times higher than allowable, right?

Does EC compliance require testing for susceptibility to static discharge?

If so, will that be a problem for the unprotected GPIO pins?

Are you expecting to achieve compliance without an enclosure?

Are you intending to achieve UL certification? If so, might that require a power switch?

RE: Spikes in the Ether – EMC and Compliance

e14 Contributor — Fri, 30 Mar 2012 00:59:04 GMT

Hi Pete, was the HDMI overdriving generating RF at unexpected frequencies because of clipping, or was it just that all the RF emissions from the HDMI connector were higher because of the higher output level? I ask because I remember some pretty awful RF spectrum spreads that people got when they used custom firmware to boost the transmission power of their Linksys WRT54G access points - there it looked like clipping was generating a huge spray of RF at frequencies not seen when the amplifier was transmitting at the designed power.

A good tight connector fit also seems to be pretty important to HDMI signal integrity... (otherwise the impedance presented by the cable to the source is not as well matched? I just hit the limit of my RF knowledge. :-)

RE: Spikes in the Ether – EMC and Compliance

e14 Contributor — Thu, 29 Mar 2012 20:09:23 GMT

Great to see this post. So it sounds like a software/firmware/configuration fix is possible to meet the EMI target, without involving a hardware change? Short of being compliant out of the gate, that's certainly the best result. It's also interesting to consider the contribution of the cables. I suppose no product could be compliant if you attach the HDMI port to a good antenna. For testing purposes, can you choose any cable you like? (is there a double shielded silver plated hardline HDMI cable made...?) -edit: obviously I'm out of touch- it seems quality HDMI cables on the market now already advertise silver plating and *triple* shielding.

RE: Spikes in the Ether – EMC and Compliance

fustini — Thu, 29 Mar 2012 16:43:39 GMT

Great post - always enjoy reading your insights into the process of baking the Pi.