Friday, 6 January 2017

#2 Homeplugs

Bought a set of TP-Link TL-PA4010 Homeplug power line network adaptors a few weeks ago. I'm not usually a fan of these things as they use radio frequencies that get radiated by the mains wiring but at the moment I've nothing for the HF bands so it doesn't matter. They were also under £20 for a pack of 2.
They are supposed to be 500 Megabit but as they only have 100 Meg ethernet to connect to anything, that's a meaningless figure, even if they could manage that in ideal conditions. Anyway I set them up by doing the usual button push and they worked as well as the Wi-Fi from router to the bridge I use to connect my main PC wirelessly, with our FTTC broadband.
If they aren't 500 Mbit/s, then how fast are they in real life? I did a test with them, compared with Wi-Fi over the same distance.
For the test, I moved my D-Link DNS-320 downstairs to the living room. It's usually plugged into a gigabit switch next to my main PC. The 'fibre' modem and Wi-Fi router (Plusnet branded Technicolor TG582N) are under the TV in the living room. This is a 2.4GHz only device, with no external antennas and 4 100 Meg ethernet ports. 

Wi-Fi test
 I plugged the DNS-320 into an unused port on the router. I set my Wi-Fi bridge up again that I had been using before I got the Powerline kit, and the main PC was connected through a gigabit switch to this. Usually I power the bridge through the DNS-320's front USB port but the iPhone charger is powering it now.
I copied a 3GB file from the NAS (mapped as a drive letter in Windows 10) to the local disk. Here is a graph of the transfer

Even though the Wi-Fi kit was capable of 'N' speeds, the connection was only being made at 54Mb/s. The maximum speed just hit 40Mb/s, which is about 4.5MB/s of file transfer. This is barely good enough to make full use of my internet connection (paying for 38Mb/s but the line can do at least 65Mbps). 

Powerline Test
For this, I plugged the DNS-320 straight into the Powerline adaptor downstairs (it has a static IP address) and the upstairs Powerline into the gigabit switch.

Both devices were on the same ring circuit (House Sockets) - there is a second ring circuit for Kitchen Sockets, which might affect the speed as there is extra cable and circuit breakers to go through but these are the most typical places you would plug in powerline adaptors.

Powerline beat W-Fi by 75% over the same distance, copying the same 3GB file. 
It was also a more stable connection, giving over 7.5MB/s of file transfer. 

The interference given out by these on HF affects mostly those frequencies outside of the amateur bands, as amateur radio frequencies are notched out, with about 50KHz guard band at the edges. On other frequencies though, there is a lot of noise from them, which even on a portable radio can be heard out in the street. When they are idle, the noise is a bit like car ignition noise (very short pulses which may be caught by the radio's noise blanker), but as soon as any data is transferred, the noise becomes continuous. Below 27.95MHz there isn't any limiting of interference to the CB channels.

What would you need them for?
For most people using Wi-Fi devices around the house on the internet, not very much. I don't like Wi-Fi on desktop PCs, as any antenna is going to be round the back, between a metal case and a wall, surrounded by a load of cables (or it's going to be inside a metal case). It's also another thing to install and take up a USB port if it's a USB adaptor. If you have some kind of file server on the network, it's good to have it wired to at least one PC/Mac to get stuff onto there quickly. That's when you would have a permanent link back to wherever the internet and Wi-Fi was coming from - ideally wired but powerline or Wi-Fi bridge if that's not possible. 
But if you live anywhere near me then absolutely DO NOT buy them (or get Sky Q)!

The network in the home is actually the bottleneck now in most areas - it can be faster to download even a big file from the internet than to transfer it over Wi-Fi between two devices in the same house (everything has to be transmitted up to the access point then back down). 

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