2.4 Ghz Network

Ham Radio Computer linking project in Northamptonshire. Nptonhams - Nptonhamnet

The 2.4Ghz linking project.

What you need to join the Network.

If you are in range of an access point station in Nptonhamnet.

If you receive a strong signal.

A radio enabled laptop or computer only.

If you have a low strength signal.

A WiFi radio card with an antenna socket. An outdoor omni directional antenna.

If you have a poor signal.

A WiFi radio card with an antenna socket. A dish antenna with a short feeder run.

If you are not in range of an access point.

Why not get together with another station and get your area linked.

One station who can 'see' a distant node needs an antenna with gain and an access point configured as a repeater.

The equipment needed is out there, reasonably priced and offers a chance for home construction of antenna's.

Notes on the 2.4GHz WiFi System.

Licence free consumer products use some shared channels which are in the Amateur band.

Consequently we can use those channels and antenna's with gain to increase the ERP to levels greater than legal for the licence free only channels.

G3ZJO is on Channel 2

If you are in range look for SSID nptonhamnet.

The system is secure.

You will need the password to access and your computer will be 'registered' as an authorised machine. I have no problems with trusted non amateur locals having access to Windows shared folders, perfectly legal as they can use the shared unlicensed frequency. This could be useful as promotion in the community for Ham Radio as a hobby.

The story so far

Phil G4IIO visited Adelaide Australia in 2004 here he met the local Hams and saw a community project in operation. Computers were linked across the city using the 2.4Ghz licence free WiFi equipment available in the local store.

This prompted Phil on his return to start tests with Simon G1IRG, despite local obstacles, trees and buildings, with a little effort and small dish antennas a link was soon up and running over the distance of approximately 1km. No more need Simon put on his boots and mackintosh and venture out in the pouring rain to collect a CD from Phil with that vital bit of software on it. Just pop it into Shared Folders and it is there for download.

Phil put forward to the local ham Radio population the idea of extending this to a full area network, several station expressed interest including me. I suppose most then did the same as me, I can 'see' neither station so there is nothing I can do to get the ball rolling.

Keith G4YKE expressed his wish to link, he is over 3 miles from me and 'through the houses' if I could connect to him and I acted as a corner point there is still no way of making a network with the other two distant stations. However if everyone puts forward the reason why it cannot be done then the project will never go forward. If we start pockets of isolated activity and show that it works then all that is needed is another station to join in and eventually we will get a network.

So after consultation of the map the tests started. View Map of the path. This aerial view shows a mainly open path, within 80m of my QTH there is a row of houses, at about half way there is a high spot with trees. The tops of these trees could be in the way. Radiomobile path plotting showed no higher ground level between us.

There is a gap between the row of houses, if I climbed on the dividing garden wall at my QTH I could see houses between the trees, but who's houses. G4YKE put on his sodium garden light, as the wind blew the trees 2.5Km away swayed and the light flickered.

The gap View the Gap. was only visible from around a meter out from my house any antenna would need to be out that far from the wall. This photo shows the dish mounted on its arm and the gap it looks through. This dish position was determined by geometry to enable the view but prior to obtaining the radio gear how do we prove the position is visible at G4YKE. I raided the kitchen for aluminium foil, wall-papered the dish with this and mounted a 20W car indicator bulb in an old torch reflector at the focal point of the dish. With binoculars from an upstairs room Keith could see this and a contact using morse code was made.

Interestingly I wandered the fields and hedgerows as far as 2.5km and I could see this focused light. View Night Photo Even on a sunny day I could spot it, often my house was not where I expected it to be when viewed from some points along the path, this was an entertaining exercise in its own right.

With light waves flying through both ways it was time to try RF. I fitted a PCI WiFi card into my PC, modified by removing the fitted antenna and providing a socket on a short fly lead. I produced two dishes with bowtie feeds, 35cm BSB digital dishes were brought down from the loft (I knew they would come in handy one day). I housed an access point in a ventilated lead box for loft installation, 2Kg of lead should keep the temperature steady. The PheoNet access point has a reverse SMA socket for the antenna.

After some field tests at G4YKE View Photo (Literally G4YKE in the field in front of his house with a dish mounted on a step ladder). to check the beam width and centre point. It was time to check the link from house to house. 2MB Broadband speeds were achieved with some fading of signal at times of bad weather and enhancement under high pressure misty conditions.

View the full equipment used for the link G3ZJO - G4YKE.

(c) G3ZJO 2006 All material is the intelectual property of the author,all opinions are solely personal,true and accurate to the knowledge experience and observations of the writer