[Nottingham] Apple Macs (and WiFi interference)

[Martin]

In brief-ish!

On 16/11/12 17:12, James Moore wrote:
> On 14/11/2012 20:50, Martin wrote:
[---]
>> Is this where the RaspberryPis overwhelm all users to save the Internet
>> and computing as it should be?! ;-)
> 
> I've yet to even see one of these gadgets, let alone get my stickies on
> one. Are they actually any good for anything beyond SDTV/HTPC/Jukebox apps?

Take a look on:

http://www.raspberrypi.org/


>>> Now...why the hell is my WiFi so laggy...
>>>
>>> *This one was bought for the insane discount.
>> That's just conflict with your neighbour's WiFi and interference from:
>>
>> EU standardises hamtagonistic powerline network tech
>> http://www.theregister.co.uk/2012/11/14/plt_standard/
>>
>> "The second vote on EN50561-1, the EU standard for running Ethernet over
>> mains circuits, has passed..."
>>
>> "... long opposed the standard, arguing that existing requirements that
>> no device generate undue radio interference should be applied to PLT
>> devices, which would make the vast majority of those in use today
>> illegal. ..."
>>
>>
>> Well... Those darn things are wide-spectrum broadcast transmitters after
>> all! Possibly even powerful enough to locally obliterate broadcast radio
>> and ADSL! The comments to that article are rather apt... I guess the PLT
>> manufacturers care little for interfering with other users, especially
>> so when denuding the profits of other suppliers...
> 
> I can certainly vouch for this. Someone in my neighbourhood uses PLE and
> I can tell you now, nobody for several blocks around has adequate
> grounding. The interference is enough to weaken my satellite reception
> by over 85%.

Expect a lot worse to come, and all way beyond the capability of most
mere mortal users to trace where the problem is other than to be
aggrieved with: "sometimes it doesn't work"...



>> On an unrelated note, I've had a surreal argument about the earthing for
[---]
> *By "adequate", this consists, at a minimum, of a solid copper rod of
> minimum cross section of 2.5mm^2 buried in the ground to a minimum core
> depth of 1m (BS7671). Check the document itself for guidelines on this
> simple fix, protective multiple earths, bleed earths (lightning
> conductors and antenna groundplanes) and metal grid earthing.

I suspect they are being cheapskate and have not bothered with the
"protected multiple earth" bits...

They've got the lightning conductor running to a separate pit with
earthing spike. The metal building frame itself is left electrically
floating on a concrete base. There might be pilings under the main
supports but can't be sure, and would the (concrete) pilings offer good
electrical earth grounding in any case?

I'd best check with a multimeter at the next visit to see how many volts
of mains (pickup) might be floating around on the network and the cable
cages...


The main questions are:

Is a local mains earth spike always needed for 3-phase into a building?
Or do you earth back to the substation via neutral (or is that a no-no)?

What's normally done?

Cheers,
Martin

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