[sclug] Powerline adapters

[David Given]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Neil Haughton wrote:
[...]
> I plugged one air-freshener into the power socket next to the router,
> connected it to the router with one of the cables and pressed a big button
> on it until a light stopped flashing. Then I did pretty much the same thing
> upstairs to the PC. Switched on the PC and oila! I had an internet
> connection - and have had ever since. Brilliant! How painless can things be?

I have a couple, too. I got the 200Mbps Homeplug AV versions, which
turns into a real-world speed of about 7MB/s between my two machines.
Setup was a bit tricky --- mine didn't have autoconfigure buttons, and I
wanted to be absolutely sure I had a decent key on them, so I had to
install drivers onto a Windows machine at work at set them up there
(with the world's most horrible front end app). Since then, they've been
brilliant. Much faster than wireless, much less hassle and with no
exotic drivers to install.

[...]
> how can I
> check the actual transfer speed between PC and router? Is the a Linux tool
> that wil do this for me?

You need some service on the router that will generate or receive data.
I don't know what your router's running, unfortunately.

I've got a Unix on both ends and so can measure speed across my network
with nc, and pv. On chur, the machine on one end of the link:

$ nc -l -p 9999 > /dev/null
(sits and waits)

On hilfy, the machine at the other:

$ cat /dev/zero | pv | nc chur 9999
25.2MB 0:00:04 [5.93MB/s] [   <=>                      ]

The first command used nc to waits for an incoming connection on port
9999, and writes the result to stdout (which we discard). The second
command generates junk data, pipes it through pv which gives us a nice
rate measurement, and then pipes it to nc, which connects to chur on
port 9999 and transmits the data.

(I've frequently used nc like this with real data to shift big chunks of
stuff from machine to machine.)

> Lastly I have read some stuff about how these devices 'steal' shortwave
> radio bandwidth (by making the unshielded household electrical cables a
> large transmission antenna) and Have To Be Stopped. My radio engineering
> knowledge is 30 years old now and could use some WD40, but I am at a loss
> about how this can be because as far as I can see the Powerline devices are
> superimposing a data signal onto a 50Hz carrier.

AFAIUI --- and I'm *not* a radio engineer --- the signal in fact uses a
whole bunch of high-frequency carriers from 1.8MHz to 24MHz, heterodyned
on top of the 50Hz mains frequency. The problem with radio noise, again
AIUI, is that cheap foreign imported powerline adapters don't comply
with UK regulations and avoid using frequencies reserved for other use.
So it's not an issue with the devices as such, just the illegal use of
unauthorised ones.

Here's some content-light marketing blurb:

http://www.powerlinenetworking.co.uk/content/view/144/25/

Now, I just wish that somebody would get a clue and produce combined
power-over-ethernet HomePlug devices. They'd be really useful.

- --
???? ?????????????? ????? http://www.cowlark.com ?????
? "There is nothing in the world so dangerous --- and I mean *nothing*
? --- as a children's story that happens to be true." --- Master Li Kao,
? _The Bridge of Birds_
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.9 (GNU/Linux)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/

iD8DBQFK+xgZf9E0noFvlzgRApVDAJ9eCtiXazihKg4e2hz9PMP0o03rvgCfVYuK
CkqbxTEaeOvj+JX5zQeHQdQ=
=g060
-----END PGP SIGNATURE-----