DIY DX WiFi?

[Gordon Henderson]

It's not just power - it's got a lot to do with the hardware/software that decodes the radio signals on the reciever... When I was experimenting with kit some years back, I found that DLink were utterly rubbish in that recpet and were very poor at suppressing reflected signals. So when they were in a good line of sight situation, all was well, but make it non-line of sight, or in a otherwise poor reception area, and the reciever would have real problems sorting out duplicate packets - as a result throughput was dramatically reduced...

They may have fixed this by now, but I did speak to their technical people, but they didn't seem too interested... As as result when the time came to deploy several 100 recievers, they didn't get a look-in.

I've heard (and no-ones ever refuted this, it *may* be UL!!!) that the radiated power avalable in the 2.4GHz range is all down to the amount of radiation a domestic microwave oven is allowed to leak... People make such song and dance about whinging about the power levels of WiFi when a mobile phone is allowed to chuck out some 40 times more power...

The reality is that no-ones going to come after you ... unless you start to cause interference... One town we installed in complained that we were interfering with the town CCTV system - which also used the 2.4GHz band (it's also knows as the ISM band - Industrial, Scientific and Medical, used for instrumentation of various sorts, and low power analogue CCTV, etc.) As our kit was off the shelf stuff, we were inside the limits, and once we knew that their kit was on the 2,4GHz band, we really really wondered how they were getting the signal from the cameras back to the base, as we really couldn't get signals into the areas they were getting signals...

There are 2.4GHz amiplifiers avalable... However if you are not careful, you'll end up amplifying noise too. (Signal to noise ratio being important here) I always try to get the output power set as low as possible which will maintain a good signal rather than just set it to max. (On units which allow you to vary the power)

If WiFi is out of the question, I assume you have power down to the workshop, so looking into Ethernet over mains might be an answer...

Gordon

[Gordon Henderson]

link we installed was a shade over 7.5Km. Omni at one end, and a grid parabolic at the other end.

We also installed a 17.5Km link using 5.8GHz kit with 2' dishes at each end and very good line of sight... (Which my home broadband comes over!) It got a little unreliable last year when one of the dishes filled up with snow driven into it in a gale )-: We also found that it wasn't properly aligned - we'd just guessed one end because we couldn't see it - it turned out to be 15 degrees out which over that distance was quite considerable

- we reckoned we were seeing one of the side-lobes rather than the main beam. It's been rock solid since we went back and aligned the dishes properly.

Theres a lot of hackers out there who go for distance records - 50 miles or something was the last one I heard about I think, but I gave up looking as it gets a bit silly - mountian top to mountian top with dishes the size of cars...

Hm. solwise do power over ethernet kit-

quid each for the cheaper level ones - might be worth investigating...

Gordon

[Gordon Henderson]

OK. You are in with a good chance. I'd still go with an outdoor antennae if possible though.

I'm not that hot on the technical side of things (Internet, IP, routing, etc. is my area of expertiese, however you learn a lot when working with the radio heads!)

As far as I could tell yes - the radios insude the units are matched the the flatplate (actually they look like a foil pie dish!) units to keep the ERP to legal levels...

Isn't there is distance limit of USB cables though? If not, it might be an option in the workshop then. I've run > 50M cables to these units in the past.

It can be done, but you need expensive cable and connectors - I've used some units which have external co-ax plugs and cables though, but we still ran ethernet right up tothe device, then connected it to an omni or grid parabolic via a veryshort patch lead.

Yagis, etc. are all just differetn types of antenna. You need a base station which has a co-ax outlet and a bit of cable to connect to the antenna. You have to do sums like multiply the output power by the gain of the antennae then subtract the losses in the cables and connectors - in extreme cases, adding an external antennae can actually reduce the ERP.

When we did tests, Netgears seemd reasonable, and I have a really old Belkin at home which I use from time to time and it seems better. DLink gave the worst performance of the lot of them.

Indeed - and this is why commnity WiFi projects will never fly )-: It simply costs to much to build the infrastructure and people just won't pay the real home install costs - it was costing us something like £250 per punter in real terms to put a unit on the side/roof of their house.. charging them £99 which was all they would be prepared to spend meant we made a loss for a very long time...

Gordon

[tony sayer]

In article , Andy Hall writes

The 16 dB gain ones with the 2.4 Ghz units Seano from the same company but with "useful" output, pretty close to the aerials so cable losses were quite low. It's out in the sticks and carries broadband to a small industrial estate who are still too far of the BT or ntl networks to get anything useful.

Alignment was very simple as you can see either end from the other....

[tony sayer]

Up in the 10 to 12 Ghz band....

[Mike]

No, it's the ERP that counts (as well as a host of other specs such as harmonics and IM which come from the transmitter but can be rendered out of spec by attenna 'gain'.

That said the Wi-Max stuff drives a horse and cart through such limits ! :-)

[T i m]

For USB 1(.1) I believe its 5m before it needs to go though a hub. I think you can have 4 hubs so 5 'segments' giving 25m or so? These often look like an 'extension lead' but are infact single port hubs.

I've run > 50M cables to these units in the

In theory you should be able to go up to 100m for Cat5 ?

And it all seems a bit messy .. weird connectors etc?

All the best ..

T i m

[John Rumm]

You have probably had all the relevant answers already, but I would add my vote for the solwise kit , we use a fair mount of it without any problems.

I can't see you having any problems with a standard AP and a yagi (regarding power levels etc).

The network over mains units may also do what you want assuming you already have a mains feed out to your workshop.

Myself I just ran a long cat5e down to it ;-) (although the WiFi does reach anyway)

Best kit to use would be a Wireless AP that has a reverse SMA connector for the antenna. You can then ethernet it to a suitable location and run a short RF elad to the yagi.

[Capitol]

Didn't build the can antenna, which looked a pig to couple into and was extremely ungainly, but using a modified double diamond yagi, for receive and passive reflection, achieved vastly improved range and directional signal reception, which knocked out the microwave interference. Check my post on 2.4GHz some weeks ago. Pretty easy to build.

Regards Capitol

[John Rumm]

Ethernet spec alows for 305m (1000') per segment... if you want more than that then you need a repeater (i.e. a hub) along the way (and you can power that over the spare wires in the cat5 if you want!)

[tony sayer]

Yes second that. Their 2.4 MHz boxes are a tad more meaty that most high St supplier ones:)

[Mark Carver]

If you eat Pringles.......

[T i m]

Hi John (et al) , thanks for the update.

Currently I have a Netgear ME102 AP in the back room talking to a Q-Tec PCMCIA card in the laptop in the workshop (for test purposes) and it's ok as long as I leave the (steel) door open ;-)

Ok ..

I will run Cat5 down there alongside the power (in it's own plastic tube) but that might not be for a while ..

*IF* I can get some sort of 'box' (Ethernet remote powered doo-dah) up behind the glass over the doors of the workshop and then I should get a useable signal with the std ant.

All the best ..

T i m