[GLLUG] Charity WiFi, a bit off topic

Christopher Hunter cehunter at gb-x.org
Wed May 23 04:32:47 UTC 2018

On 22/05/18 23:01, James Holland via GLLUG wrote:
> On 26/03/18 17:56, John Winters via GLLUG wrote:
>> I've tried various brands of ethernet-over-mains devices and none of 
>> them was reliable.  They all seem to need to sit down for a rest 
>> every hour or so, resulting in a couple of minutes of no connectivity 
>> before they start working again.  Really annoying if you're in the 
>> middle of watching a film or something.
> To solve this I ping the AP every second. It works really well - much 
> better than the repeater which I tested. I use LEDE (Openwrt) on the AP.
That was an approach that I tried too, but it didn't really help.  It 
prevented the Devolo and the TP-Link power-line efforts from going into 
"sleep" mode, but didn't overcome the basic flakiness of the whole 
power-line concept.  I've used power-line communications since the 1960s 
(I built a pair of 120kHz FM mains intercoms!), and it's OK for 
non-critical applications.  However, the general lack of reliability of 
the medium, and the abysmal build quality of the equipment, conspire to 
ensure that it'll never be reliable.  Examination of several faulty 
units (of various brands) show that there's always insufficient 
isolation between the low voltage logic side of the circuit and the 
mains side.  The leakage figures on some of them were scary!

At one time, BT installations frequently included their power-line links 
- particularly when BT-TV was involved.  They'd arbitrarily throw these 
things in, charge extra for them, and then blame the subscriber's 
computer, mobile phone, TV, or even the weather for the appalling 
performance of the BT "Infinity" service.

They really should be banned - the wideband RF noise from them jams 
everything from Long Wave to the TV Bands.  When I lived in London, I 
paid for the installation of a couple of wired Ethernet links around a 
neighbour's house so that I could get fairly reasonable radio reception 
two doors away!  They returned those "Netgear" jammers to PC World and 
after a serious argument - which involved demonstrating that the DAB 
radios on the shelf wouldn't work with the things plugged in, but were 
fine when they were removed - the store manager realised that these 
efforts weren't a good idea.

The RF noise we suffer these days from cheap and nasty Switched-Mode 
PSUs, Ethernet over mains, Microwave Ovens, Induction Heaters and 
Cookers, and all the rest is becoming a real nuisance.  In most cities 
we live in a kind of "Electro-smog", which increases the power budgets 
for communications radio of all sorts, including PMR, Police, Fire and 
Ambulance, microwave links, and all the rest.  Everyone's having to 
"shout louder" to make themselves heard!


Chris (in the Suffolk countryside!)

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