David's Wireless Link to the Travelodge
Based upon much information already available on the Internet!
For more information see http://www.wlan.org.uk and http://www.turnpoint.net/wireless/cantennahowto.html all the links from those sites.
This project started out as a very simple requirement as has grown into a mini obsession hence all the other links!
After the long ago demise of free 0800 data calls from the Orange mobile phone network, I have been spending much time in a Travelodge without any Internet access. As the frequent traveller knows, only "Travelodge City's" have telephone points and even then, I'd be paying inflated telephone charges for Internet access. Fortunately, the place of work is nearby to the Travelodge, just a short hop across a couple of car parks so I thought "What about 802.11b wireless?"
I had previously considered the range to be probably too far but decided to give it ago since it was pretty much line of sight with just a few trees to go through and a small amount of brickwork around the corner of a jutting out part of the Travelodge. I started out with a NetGear ME102 access point that I had been using at home.
I had originally planned to try two NetGear USB MA101 NIC's and although initial testing showed that I could ping from the Travelodge, the signal was very weak and I then discovered the following power up ability for the access point http://www.pasadena.net/aprf/. Further testing was then done using the access point only with the increased output power. I tried the access point both hanging outside the window and inside behind glass. There was only a small signal drop so with the added security and obvious weather problems, I decided to continue with the access point inside the building, behind the window.
Click here to go straight to mark 3 of the antenna (USB Cantenna!)
(not my mod, cached copy from the now inaccessible guerilla.net)
The following picture shows the view from the location with the Wireless Access Point. Note the dark green tree in the middle, it's about midpoint.
The dark green tree can just be seen to the left of the taller tree by the front of the building. This is the view from the client side.
NetGear MA101 USB NIC on the windowsill at the Travelodge. With just the NIC on it's own and the access point behind a window, the signal received was very low, often anywhere between 0% and 7% max signal strength. The quality of the signal was ok and I could just about gain Internet access but it was liable to drop out frequently and so was too unreliable to consider a success!
During my initial test, there was a lorry parked right across my line of sight to the access point and to compound the problem, there was also a bit of rain, the resultant signal is shown in the signal strength here:-
So we move on to the waveguide antenna solution!
Removing the case from the USB NIC and mounting it to a Tesco Instant Dried Milk tub (foil lined) results in this contraption. (The Tesco's tub appears to be a branded "Marvel" product, I chose the Tesco's tin for its £1.58 price point against the Marvel product at £2.05 . The "good" waveguide designs show an N-type connector with a rod soldered in them to provide the feed. I didn't have an N-type connector (out of stock at the shop) so I decided just to dismantle the USB NIC and poke the antenna wire up into the milk tub at the appropriate point. The benefit of this is no impedance mismatches or other such problem with connectors and no signal loss along a potentially lengthy cable.
The milk tub is attached to the outside of the window by a suction cup on a flexible stalk, this was from Halfords and is simply from a mobile phone of the sort that clamps the phone and sticks to the windscreen or dashboard.
The resultant signal with the truck still in the way, shows a pretty impressive first result:-
Having waited an agonising day for the lorry to move, the improvement over the USB NIC that was just sitting on the windowsill is quite staggering to say the least!
Not content with a 50% improvement in signal received, I thought I'd try an antenna on the access point. I had brought along a dog food tin (Tesco's premium in gravy - my dogs ate the contents of this one, unlike the dried milk which went straight in the bin). Not wishing to construct anything too permanent at this stage, a hole in the dog food tin was made and the dog food tin just taped over one antenna and allowed to protude into the can at what I thought was roughly the right point and depth. For those people thinking, "what about if TWO cans were used, one on each antenna?". Go and follow the links or read about "antenna diversity", just like I did!
The best observed signal with the dog food tin upgrade yielded the following signal:-
Unfortunately, I left the whole lot outside one night and it rained causing the milk tub to get a bit soggy - RIP trust tub!
Click on to Cantenna Mark 2 for the next version and don't forget to check out the Netstumbler results on the Other Homemade Antennas link further up this page for the final results using an SMA baby food tin on a modified ME102 feeding a version of the Mark 1 cantenna with a cardboard horn. Outstanding results!!
Budget Power over Ethernet (Can't afford, or don't feel like paying for a commercial PoE unit?)
Stuff about the Linksys WAP11 (Internals and how to mount the Access Point remotely)
Online book about Microwave antennas (Nice background information about antennas)
Wireless Network Link Analysis (This is a neat site for simulating your link to see if it will actually work!)
WLAN Card receive sensitivity table (Table of receive sensitivity for many popular WLAN cards)
802.11b Wireless LAN card schematics (for a few cards, mainly Prism 2 chipset)
RF Power conversion table (Trying to compare a card with 18dBm vs. one with 30mW output power?)
WLanExpert (signal strength, antenna testing and other stuff for Prism chipset based cards)
Some Commercial Antenna & accessory suppliers:-