Network cardOver the last few years’ networking computers has become very easy, there are now many options. A few years ago I was convincing others if they had an old computer to network it with another computer. Purchase two network cards or take cards out of an old network computer from the auction. Make a crossover cable if you are using only two computers (a hub is required if you’re connecting more than two computers).
As long as you are using Windows 98SE/ME/2000/XP it is easy as ABC to join (network) two computers together. One computer can be in the bedroom and the other one can be out in the garage. The only limitation is running the network cable. DSE sell XH7900 or XH7975 10/100Mbps PCI network cards for $16. If you don’t want to open up your computer you can use two USB 10/100Mbps Ethernet adaptors XH8144 $59ea. 1m crossover cables $9ea, 3m cables $11 each. XH6812 1000Mbps network card $38ea.
USB 10/100Mbps Ethernet adaptors
USB crossover cableA year later I wrote an article how to network two computers using a USB cable (note it’s a special USB cable with a switching device in the middle of the cable). As it’s USB it is basically Plug & Play. Your network is working when the USB cable is plugged in, great for networking the main PC with your laptop or notebook. Plug in the laptop and swap files via the USB cable; can be easily extended by purchasing a USB extension cable. XH8177 supports up to 480Mbps USB 2.0 and is backwards compatible with USB 1.0 12Mbps Price $46. 12 months later I wrote article about a Bluetooth wireless 2.45 gigahertz connection and how it was possible to use two USB Bluetooth dongle (XH4102 class 1) or (XH6829 class 1) plugged into USB ports so two computers can be wirelessly networked. Class 1 can transfer data up to 75/100 metres; class 2 the more common one can transfer data up to 10 metres. Bluetooth is slow but very secure, as it uses frequency hopping, similar to FHSS but not compatible (see technical notes at end) but fast enough for most PC users (723Kbps which varies on the environment). Really good if you have a main PC and a notebook computer, it gets rid of all those wires. Up to 7 devices can be easily connected in a Piconet.
USB Bluetooth dongle
PCMCIA wireless network cardLater I was using WiFi (wireless fidelity), who wants cables when you can network via wireless. Besides in some houses it’s just not possible to run large network cables. Purchase a PCI wireless card for your main PC (XH8135 802.11b) and a PCMCA (XH8152 802.11g) or (XH6860 802.11b) card for your laptop and network anywhere around the house, out in the garden, downstairs, or even in the children’s bedroom. The IEEE 802.11 specification is a seal of approval that says the manufacturer’s products are compliant. This spec drops FHSS and focuses on DSSS because of the higher data rate it can attain. Under 802.11b devices communicate at speeds of 11Mbps whenever possible. If signal strength or interference is disrupting data, the device will drop back to 5.5Mbps, then 2Mbps and finally down to 1Mbps. Though it may occasionally slow, this keeps the network stable and very reliable. WiFi offers Ethernet speeds without wires, but you pay for it. Remember that this is still a developing technology. And if you want to throw away the cable to your printer it is easy. Use a XH8062 to connect a parallel printer to a wireless network. Price $159. See photo.
Networking today has never been so easy. And if you have a friend who has a link to City Net you can go to Manners Mall, with your Laptop and connect to the Internet. Really fast for downloading programs, if you are using the XH8152 802.11g will transfer data up to 54Mbps under ideal conditions. People walking past never realise you are surfing the Internet. Wellington for the last few years now has nodes (wireless connection points) in many areas throughout the CBD, Lambton Quay, Manner Street, Civic Square, and WCC Central Library and in University Campuses.
Printer wireless networkAnd there are access point (nodes) in many city cafes (these nodes are called CafeNet), drink your coffee, eat your buttered scone and surf the Internet. Ie: Caffe L affare, College Street, Wellington. Words of warning don’t go there (if I remember correctly) on Tuesday mornings, as it is mothers’ coffee morning. It’ not easy to surf and listen to babies balling there eyes out. More info about CafeNet at http://www.cafenet.co.nz
In February 2004 I started playing around and experimenting with some students from Victoria University. They discovered if you purchase a 76543 USB 1.1 adaptor from the US and 25m length of USB cable and mount the 76543 on top of a pole outside (as high as possible) you could network over one hundred metres. They successfully networked up to 175metres, from the top of Halifax Street, Kingston, down the road to where two other Victoria University students rent a house. Transfer rate dropped to 1Mbps DBPSK; still faster than a 56k dial up modem. If you are getting 4.1kb/sec download with a 56k modem and multiply this by 60 seconds you are getting 250,000 per minute. Therefore it takes 4 minutes to get 1 Meg. (Note the 76543 and XH6859 802.11b will transfer data at 11Mbps CCK under good conditions, but will drop back 11/5.5/2/1Mbps using auto fallback. If the range is increased it will not drop below 1Mbps DBPSK). The real advantage of setting up something like this is so students can access the University computer system. And one computer only needs to be connected to a faster cable modem to access the Internet. The other computers share the connection. The Dick Smith XH6859 adaptor looks similar to a USB memory stick. See picture below, XH6859.
One student discovered students from Massey University were using 300mm Chinese cooking sieves from “The Warehouse” to increase the range. Wanting to be different they purchased Asian sieves from Yan’s Supermarket, Hopper Street, Wellington, real stainless steel. We realised very quickly why the Massey boys were using cooking sieves rather than solid Woks. Wellington wind passes through a sieve but solid elements tend to catch the wind. These sieves make a good 2.4Ghz parabolic mesh antenna with a USB Wireless (XH6859 802.11b) adaptor mounted in the middle at the focal point. The focal point can be found easily by covering the sieve with aluminium foil and using the Sun or a very bright light to work out where the rays converge.
Cooking sieves antenna
USB WiFi adapter XH6859Hopefully (if you get it right) this will be the focus point. These sieves are not true parabolic curves but are still good enough as they reflect signals waves from a focal point as a parallel beam (similar to a head light) and also concentrate distant signals to a focal point. The 300mm cooking sieve then becomes a 15db USB driven 2.4Ghz WiFi parabolic antenna that can provide LOS (line of sight) networking over one or two KMs. By installing a USB plug in the middle of the sieve, the idea was so it could be easily replaced when the newer XH8227 802.11g replaced the XH6859 802.11b. Unfortunately the g is not like the b, it’s a much larger unit and not waterproof. The g will transmit data up to 54Mbps under ideal conditions. It also uses Auto Fallback 54/48/36/24/18/12/11/5.5/2/1. The g many be faster but does not have the range of the smaller XH6859. See picture XH8227.
Signal loss using USB cables is extremely small as you are dealing with digital signal rather than normal radio waves. Mounting an antenna high using microwave coaxial cable can sometime defeat the purpose. The decibel loss per metre (.5) can be greater than the DB (decibel) gain. You may have a 25-decibel gain at the masthead but no signal gain at the base connection point. Where as 20 metres of USB cable will have very little lost compared to 20 metres of coax cable.
Wireless - USB unit. XH8227Signal loss using USB cables is extremely small as you are dealing with digital signal rather than normal radio waves. Mounting an antenna high using microwave coaxial cable can sometime defeat the purpose. The decibel loss per metre (.5) can be greater than the DB (decibel) gain. You may have a 25-decibel gain at the masthead but no signal gain at the base connection point. Where as 20 metres of USB cable will have very little lost compared to 20 metres of coax cable.
To find out what the students’ are up to visit Massey University students web site http://usbwifi.orcon.net.nz it’s really interesting. By the number of hits this site has had worldwide it just goes to show that Kiwis can DIY as good as anyone.
John ThomsonGella@paradise.net.nz
Technical notes:SS (Spread Spectrum) means that data is sent in small packages over a number of discrete frequencies, available for use at any time.
DSSS (Direct-Sequence Spread Spectrum) devices communicate by splitting each byte of data into several parts and sending them concurrently on different frequencies. DSSS uses a lot of available bandwidth, about 22 megahertz (MHz).
FHSS (Frequency Hopping Spread Spectrum) devices using FHSS send a short burst of data, shift frequencies (hop) and then send another short burst. Since the FHSS devices that are communicating agree on which frequencies to hop to, and use each frequency only for a brief period of time (less than 400 milliseconds) before moving on several independent FHSS networks can exist in the same physical area without interfering with each other. FHSS devices generally send data on just two or four frequencies simultaneously; they only use 1MHz or less of the available bandwidth.
SWAP (Shared Wireless Access Protocol) a hybrid standard (similar to FHSS, but not compatible). SWAP uses six voice channels based on the Digital Enhanced Cordless Telecommunication (DECT) standard and the 802.11 wireless Ethernet specification for data. SWAP make 50 hops per second and transmits at 1Mbps. The new “DECT” digital phones that DSE (Dick Smith) sells conform to this standard.
