Saturday, July 21, 2007

ERROR 734: The PPP link control protocol was terminated

ERROR 734: The PPP link control protocol was terminated
Redial Canel more info

Click your START menu
Click CONTROL PANEL
Select PHONE AND MODEM OPTION
In case is not configured select NIGERIA from the list and 234 for the AREA CODE
Select the "MODEMS" tab
Select the modem you are connecting with which
could either be "bluetooth Dun modem" or "phone model USB modem"
or "phone model infrared modem"
Select PROPERTIES
Selecting MODEM tab, you can increase your port speed to boost the speed of your connection.
Select DIAGNOSTICS
Click QUERY MODEM if success
Go to the ADVANCED tab
In the EXTRA INITIALIZATION COMMANDS
Type
AT+cgdcont=1,"IP","web.gprs.mtnnigeria.net" for MTN network
AT+cgdcont=1,"IP","wap.ng.celtel." for CELTEL network
AT+cgdcont=1,"IP, "glogwap" for GLO network

Select OK and OK again to exit
Now you can try and DIAL entering your neccessary parameters
MTN
user name WEB
password WEB
DIAL: *99***1#

CELTEL
user name WAP
password WAP
DIAL: *99***1#

GLO
user name WAP
password WAP
DIAL: *99***1#

It will register and Authenticate and you are up
Happy browsing.......

Friday, July 20, 2007

Computer Networking Definition

Computer Networking Definition
Definition of "Computer networking" is the engineering discipline concerned with communication between computer systems. Such communicating computer systems constitute a computer network and these networks generally involve at least two devices capable of being networked with at least one usually being a computer. The devices can be separated by a few meters (e.g. via Bluetooth) or nearly unlimited distances (e.g. via the Internet). Computer networking is sometimes considered a sub-discipline of telecommunications, and sometimes of computer science, information technology and computer engineering. Computer networks rely heavily upon the theoretical and practical application of these scientific and engineering disciplines.
A computer network is any set of computers or devices connected to each other. Examples of networks are the Internet, a wide area network that is the largest to ever exist, or a small home local area network (LAN) with two computers connected with standard networking cables connecting to a network interface card in each computer.
Networking Methods
Networking is a complex part of computing that makes up most of the IT Industry. Without networks, almost all communication in the world would cease to happen. It is because of networking that telephones, televisions, the internet, etc. work.
There are two (broad) types of networks in existence at the moment. These are:
Local Area Network (LAN)
A Local Area Network is a network that spans a relatively small space and provides services to a small amount of people. Depending on the amount of people that use a Local Area Network, a peer-to-peer or client-server method of networking may be used. A peer-to-peer network is where each client shares their resources with other workstations in the network. Examples of peer-to-peer networks are: Small office networks where resource use is minimal and a home network. A client-server network is where every client is connected to the server and each other. Client-server networks use servers in different capacities. These can be classified into two types: Single-service servers, where the server performs one task such as file server, print server, etc.; while other servers can not only perform in the capacity of file servers and print servers, but they also conduct calculations and use these to provide information to clients (Web/Intranet Server). Computers are linked via Ethernet Cable, can be joined either directly (one computer to another), or via a network hub that allows multiple connections.
Wide Area Network (WAN)
A Wide Area Network is a network where a wide variety of resources are deployed across a large domestic area or internationally. An example of this is a multinational business that uses a WAN to interconnect their offices in different countries. The largest and best example of a WAN is the Internet, which is the largest network in the world.
Wireless Networks (WLAN, WWAN)
A wireless network is basically the same as a LAN or a WAN but there are no wires between hosts and servers. The data is transfered over sets of radio trancievers. These types of networks are beneficial when it is to costly or inconvenient to run the necessary cables. For more information, see Wireless LAN and Wireless wide area network
In order for communication to take place between computers, mediums must be used. These mediums include Protocols, Physical Routers and Ethernet, etc. This is covered by Open Systems Interconnection which comprises all the processes that make information transport possible.

Networking For LAN

Networking For LAN
Wiring up a LAN (local area network) can be very easy, or it can be very difficult – it all depends on the size of your network, and how you’re trying to go about it.
For a very small home network, you can get by without using any special equipment except the wires. If you want to use a network to share Internet access or a printer, just plug an Ethernet cable into the computers you want to network, and then use the simple networking features that are built into Windows, such as Internet Connection Sharing. This approach has many downsides, though – you’ll need an extra Ethernet card in each computer for every extra computer you connect to the network, for one.
Instead of connecting each computer to the next, it is better to simply connect all the computers to a central router. This is a very efficient way of connecting computers together, as the data you send will be quickly and easily routed to its destination: the data goes to the router, which knows which wire to send it down for it to reach the destination address, and simply sends it that way. This also allows you to turn on and off computers as you please with no ill effects, as the router is always-on.
If you want to connect more devices to the network than the four or five ports on a router will allow, then you need to get a network switch. This allows you to create a separate sector of your network especially for one group of devices. For example, you might have your computer and your printer both plugged into a switch. The computer and the printer can then communicate between themselves without the data needing to travel out onto the wider network – but if they want to send to or receive from the wider network, they can do that too.
John Gibb is the owner of ethernet resources For more information on ethernet check out http://www.ethernet-intelligence.info

Computer Networking - How It Works

Computer Networking - How It Works
Computer networking is a process of sharing data and shared resources between two or more connected computers. The shared resources can include printer, Fax modem, Hard disk, CD - DVD Rom, Database and the data files. A computer network can be divided into a small or local area network, a networking between computers in a building of a office (LAN), medium sized network (MAN), a network between two offices in a city and Wide network (WAN) a network between the computers, one is locally and the other can be thousands of miles away in any other country of the world.
WAN connectivity is achieved by a network device known as “Router”. The internet is the world’s largest WAN network, where millions of computers from all over the globe and connected with each other.
Networking is the practice of linking two or more computers or devices with each other. The connectivity can be wired or wireless. A computer network can be categorized in different ways, depends on the geographical area as mentioned above.
There are two main types of the computer network client-server and peer to peer. In the client server computing, a computer plays a major role known as server, where the files, data in the form of web pages, docs or spread sheet files, video, database & resources are placed.
All the other computers in the client/server network are called clients and they get the data from the server. In the peer to peer network all the computers play the same role and no computer act as a centralized server. In the major businesses around the world client-server network model is in major use.
A network topology defines the structure, design or layout of a network. There are different topologies like bus, ring, star, mesh, hybrid etc. The star topology is most commonly used network topology. In the star topology, all the computers in the network are connected with a centralized device such as hub or switch. Thus forms a star like structure. If the hubs/switch fails to work for any reason then all the connectivity and communication between the computers of a network will be halted.
In the network, a common communication language is used by the computers and the network devices and this language is known as protocols. The most commonly used and popular protocols on the internet and in the home and other networks is called TCP/IP. TCP/IP is not a singleprotocol but it is a suite of several protocols.
A network can be a wired or wireless and TCP/IP protocol can work both in types of network.
A data flow in a computer network can be divided into seven logical layers called OSI layersmodel that was developed by Intel and Xerox Corporation and was standardized by ISO.
1. Application layer
2. Presentation layer
3. Session layer
4. Transport layer
5. Network layer
6. Data Link layer
a. Media access control sub-layer
b. Logical link control sub-layer
7. Physical layer.
A network can be divided into different scales and ranges and it depends on the requirement of the network and the geographical location. Computer Network can be divided into Local Area Network, Personal Area Network, Campus Area Network, Wireless Local Area Network,Metropolitan Area Network and Wide Area Network.
There are several network connection methods like HomePNA, Power line communication, Ethernet and Wifi connection method.A network can also be categorized into several different types based on the services it provides like Server farms, Storage area networks, Value control networks, Value-Added networks,SOHO network, Wireless network and Jungle networks.
B. Bashir manages this website Networking Tutorials and regularly writes articles on various topics such as Computer Networking Network Troubleshooting Tips Wireless Networking, Computer Hardware, Certifications, How Tos, Network Security Guide and computer tips.

How To Design Network Server

How To Design Network Server
Network server is a most important component of a computer network because the entire computer network is administered, controlled and managed through it. Before designing a network server for your organization, you should have the adequate knowledge about the following things.

Server Processor

Processor is a heart of the CPU. It processes all the commands, instructions and commands and execute them to perform certain actions. Pentium processors are very reliable in performance and speed and trend is growing to use the multiprocessor servers to share the load on each processor. If one processor fails to work due to any reason, there is no effect on the other processor in the same server so it’s a wise decision of the network administrators to use the multiprocessor server for company’s network.

Hard Disk

Hard disks are used to store all the data in permanently. Hard disk is a mechanical device and while selecting the hard disk you should consider the S.M.A.R.T (Smart Monitoring and Reporting Technology). This technology monitors the hard drives and predicts the any failure in the hard drivers. Today, most of the server providers provide hot swap disk drives, this means that if one there is any error occurred in the hard drives, it can be replaced with the other hard drives while the server is in the working mode.

Clustering

In a clustering environment, two or more servers operate as a single server and the failure of the one server does not affect on the other servers. Clustered environment has the benefits such as high performance, reliability and load balancing.

Memory Performance

While selecting the physical memory for the server it should be considered the memory support Error Correcting Code technology. ECC technology fixes and repairs any single bit errors and report the multi bit errors. High memory is very vital for the server for its best performance, speed and continuous work.

Power Supply

Most of the computers come with the multi power supplies. This means in case of failure of the one power supply, does not affect on the other power supply in the same computer and in this way computer works normally. Multi power supplies are hot swappable like the hard disks i.e. faulty power supplies can be replaced with the new ones while the server is in the working mode.

UPS

UPS or uninterrupted power supply are very important in a network environment because a sudden jerk of the electricity may cause of the hard drives or mother boards of the server as well as the other computers in the network. A UPS normally provide a backup of 3-4 hours and during that time server and other computers can be setup and the files or other data can be saved.

Cooling Fans

The cooling system inside the server is provided by the cooling fans. Cooling fans pull the cool air inside the server and through out the heat from the server. The failure of the cooling fan results in the automatic shutdown of the server due to the high buildup of the heat. Many vendors of the computer systems are providing the hot swappable cooling fans.

Computer Monitoring Hardware

There is a specially designed adapter to monitor the performance of the different parts of the hardware of the computer. This adapter can also be controlled by a modem remotely.

Computer Monitoring Software

Different computer monitoring software is available in the market and their main purpose is to monitor the performance of the server and the client computers.

Data Server Location

Network server should be placed in a dust free, cooling capable and clean environment and only the authorized users should be allowed to enter in the server room.

Hopefully my above mentioned tips will help you building a better server for your computer network

B. Bashir manages this website Networking Tutorials and regularly writes articles on various topics such as Computer Networking, Network Troubleshooting Tips Wireless Networking, Computer Hardware, Certifications, How Tos, Network Security Guide and computer tips.

Computer Networking Solutions For Small Businesses

Computer Networking Solutions For Small Businesses
Many terms of the computer networking fundamentals for small businesses have come from the physical world of transportation. Some examples of such terms are ports, hubs, bridge, switching and routing. However, this simile is not unjustified because networks have same importance regarding the boom of the information era, as the transportation to the industrial era. Both computer networks and transportation system require very sound infrastructure.

Computer Networking is connecting the Computers: Most fundamental form of computer networking goes back to connecting any two electronic equipments for the transfer of data between them. Third equipment only helps the communication of data. However, connecting a printer to computer simply with the help of a USB cable is not called a network. It will be a part of the network if connected with router or switch. Advent of Internet has forced the most of the companies to think about the computer networking. No matter how small business you are running, you need to have computer-networking facilities for publicity, email and online marketing of your products and services. If you do not have a well-established network of computer, your competitors will leave you behind in contacting the prospective customers.

The Biggest Advantage is File Sharing: File sharing is perhaps the most talked about component of the computer networking fundamentals. File sharing is simply centralized grouping and organization of data files on a network server. Availability of all the data files at one place makes managing documents and data easier. Furthermore, you can also avoid the inconvenience caused by the inconsistant scheme of work among the different departments of the business. The newer versions of the network operating systems give tremendous control to the administrator. He is in complete control whether a person can get access to a particular file or not.

Sharing of Printers Saves Both Time and Money: Second important component of the computer networking fundamentals for small businesses is printer sharing. It saves a lot of money and time that you would have spent on the purchasing and maintenance of printers. The printers connected to the computer network have more features than those connected to single computers.

Email: One should also learn the importance of email to get the full understanding of computer networking fundamentals for small businesses. Group email facilitates fast and effective communication among the employees. Small business can also improve their scheduling, task assignment and contact management with the help of group or internal email. Moreover, in-house communication of documents is better than faxing because group emails are less expensive easier and unbelievably fast.

Alexander Gordon is a writer for http://www.smallbusinessconsulting.com - The Small Business Consulting Community. Sign-up for the free success steps newsletter and get our booklet valued at $24.95 for free as a special bonus. The newsletter provides daily strategies on starting and significantly growing a business.

Business Owners all across the country are joining "The Community of Small Business Owners” to receive and provide strategies, insight, tips, support and more on starting, managing, growing, and selling their businesses. As a member, you will have access to true Millionaire Business Owners who will provide strategies and tips from their real-life experiences.

Computer Network Devices And Component

Computer Network Devices And Component
A Computer network is comprised of different devices to share, transmit, and boost the signal, voice and data. Network devices or components are the physical parts connected to a network. There is a large number of the network devices and are increasing daily. The basic network devices are: Individual Computers, Server, Hub, Switch, Bridges, Routers, Modems, Printers, DSL Modems & Routers, Gateways, Network Interface Cards, Cabling & Wireless access point. The following is a overview of each of these network devices.

INDIVIDUAL COMPUTERS: The personal computer is usually a desktop computer, a work station or a laptop. The personal computers are most widely used in any organization or for personal use. The individual computers are the most common types of the microcomputers.

SERVER: A server is a computer on a network, which process request and is used to share the data and resources among the other computers in a network. A server stores all the necessary information and provides the different services like, workstation computer’s logon access, internet sharing, print sharing, disk space sharing etc. There are different types of servers e.g File and print server, database server, proxy server, Fax server, backup server etc. A database server stores all the data and software, which may related to the certain database and it allows other network devices to access and process the database queries. A file server is used to store the data of any user on the network and a print server manages one or more printers in a network. Similarly a network server is a server that manages the network traffic.

NETWORK INTERFACE CARD: Network interface cards are attached with the computer or other network devices and are used to provide the connectivity between the two computers. Each network card is specifically designed for the different types of the network like Ethernet, FDDI, Token Ring and Wireless Networks. The Network card operates on the first and second layers of the OSI models i.e Physical layer and datalink layer specifications. NIC basically defines the physical connection methods and the control signals that provides the timings of the data transfer over the network.

HUBS: Hub is a simplest network device. The function of the hub is broadcasting i.e data is forwarded towards the all ports of a hub, regardless of whether the data was intended for the particular systems in the network or not. Computers in a network are connected to a hub with a twisted pair (CAT5) cables. There are two types of the hubs. 1. Active Hubs. 2. Passive Hubs.

SWITCHING HUB: The Switching hub (also called “switch” is the most advance shape of the basic hub. In a basic hub all the computers are connected with the hub and the speed of the network is defined by the slowest computer network card connected. For example if you have 10/100 Mbps cards in a network and only one card of 10Mbps speed then the system cannot run faster than the 10 Mbps. Now if you have a switching hub in a network, it will allow all the faster connections in the network to remain at the higher speed and still interact with the 10Mbps system.

SWITCHES: Switch is a intelligence device than hub. Switch is a layer 2 device. Swith provides the same function as a hub or a bridge but it has the advance functionality of connecting the two computers together temporarily. Switch contains the switch matrix or switch fabric that can connect and disconnect ports. Unlike hubs, switch only transmit or forwards the data to the destined computer and it does not broadcasts the data to all its ports.

MODEMS: Modems are the devices, which are used to translate the digital data into the analog format and vice versa. It performs the two main functions. Modulation and demodulation. A modulated data can travel across the conventional telephone lines. The modem modulates the signals at the sending end and demodulates at the receiving end. Modems are required for different types of the access methods such ISDN, DSL and 56K data modem. Modem can be the internal devices that plug into the expansion slots in a system or can be external devices that plug into the serial or USB ports. In Laptops, PCMCIA cards are used for this purpose and many new laptops having the built in integrated modems. The specialized devices are designed for use in the systems such as handheld computers. In ISPs where the large scaled modems are required, rack-mounted modems are used.

ROUTERS: Routers route the data between two logically and physically different networks. A Router has the capability to determine the destination address for the data and hence provides the best way for the data to continue its journey. Router gets this capability through its software called routing software. Unlike Switches and Bridges, which use hardware configured MAC address to determine the destination of the data, router uses logical network address such as IP address to make the decision in determining the destination of the data.

GATEWAY: A gateway performs the function of translating the data from one format to another format without changing the data itself. A gateway can be a device, system, software. A computer with two NIC cards can function as a gateway. Router acts as a gateway e.g a router that routes the data from a IPX network to a IP network is technically a gateway. The same can be said of translational switch converts from a Ethernet network to a token ring network.

CABLES: There are two most common types of the cables. 1. 10baseT and 10base2. 10baseT is a four paired cable. 10baseT has further two types 1. UTP (unshielded twisted pair) and 2. STP (shielded twisted pair. STP is most secure cable covered with the silver coated twisted paper to protect the cable. On the other end Thin 10base2 looks like the copper coaxial cabling that often used to connect TV sets and VCR. 10baseT/Cat5 cables are most commonly used cables to connect the computers. It has the connector, (like a telephone connector) called RJ45 connector.

Twisted pair cables are ideal for the small, medium or large networks.
My recommendation for using cables for networking is to use 10baset/Cat5 cables

Friday, July 13, 2007

Easy Homemade 2.4 Ghz Omni Antenna

WLAN antenna 2.4 GHz Do-It-Yourself

Homebrew outdoor antenna to 2.4 GHz band.

Antenna gain is comparable to panel antennas including the Freedom Antenna Set sold in Finland. Comparing is made simple by connecting antennas to same computer with Orinoco WLAN card and indicating results in Link Test of the Client Manager. My antenna has been found about 2 dB better gain than the Freedom antenna, which is specified as 12 dBi antenna. And prices ... Oh, I need not even mention this! In Europe there is a maximum allowable output power of 20 dBm (100 mW) because of the ETSI standard we use. While Orinoco "red" card is transmitting 8 dBm signal and my antenna gain is about 14 dBi there has to be only 2 dB cable and connector loss to keep output level below 20 dBm. The Orinoco Adapter Cable takes about 1 dB and H1000 antenna cable takes 2 dB/10m. So using 5 metres antenna cable there is no risk of exceeding the output power within the ETSI standard. This antenna can also be built without the Ring to decrease antenna gain if needed especially with very short antenna cable.

Dimensioning

The very first point in antenna dimensioning is to calculate the wavelength (the Lambda character has been replaced with letter L ):
L /mm = 300 / (f/GHz) -> at 2.45 GHz L = 122 mm.

Antenna picture without mast fasteners:

With the cover Without the cover

Main parts can been found even in mama's dish cabinet but maybe safer to buy them from a department store. The Reflector is made from an aluminium cake pan and the Cover from a plastic microwave bulb, both 240--250 mm dia. The pan must be straight and smooth without profilations and the sides will be orthogonal with the bottom. If you find a pan made from stainless steel may be that may be better. I used a pan from italo ottinetti code 140024 , whose sides were 60 mm and I cut them to 32 mm.

Other parts needed:
A piece of copper water conduit, internal dia 10 mm, length below 40 mm
A piece of brass rod, outer dia 4-4.5 mm, length < 40 mm
Copper wire about 2 mm dia, length < 70 mm
N-connector, panel socket
A couple pieces of tinned steel sheet e.g. from tin can
A piece of PVC coated electric wire 1,5 mm2
Screws and bolts M3, solder tin etc.


Antenna construction:

The Reflector (aluminium pan) dia = L x 2, the height of the sides = L/4.
In the centre of the bottom there is the N connector to left and the dipole to right. A distance from bottom to the dipole is little more than L/4. The Dipole is mounted with an air-insulated coaxial type foot, whose impedance is 50 ohm and length L/4. Inner wire of the coaxial is made of 4 to 4.5 mm rod or conduit and shield made from split copper conduit which internal dia is 10 mm. To the right of the dipole there is a disc whose dia is L x 0.4 (= 49 mm) and distance from the dipole is again L/4. Disc material can be thin aluminium or tinned steel sheet.

At same distance as the disc, there is also a ring made from pvc-coated electric wire 1,5 mm2 by binding it to ring diameter about L x 2. It is not neccessary to short the ends of the ring, I left ~ 1 mm space. If you want you can short the ends together as well. PVC coating on the wire has no magic, you can use e.g 2 mm clear copper wire as well.

I mounted the Disc and the Ring to the plastic cover made from microwave oven bulb. A piece of plastic sheet and glue are needed to mount the disk. The ring I glued inside the cover, so the diameter of the ring becomes somewhat smaller than L/4.

Assembling:

The sides of the reflector (cake pan) must be L/4 or 32 mm, so extra height must be cut away. In the centre of the pan there will be a hole 12 dia and four 3.5 mm holes according the N-connector. The feet of the dipole is made of split copper conduit and inside it a rod or a pipe. The impedance of the feet must be 50 ohm which actually means the ratio of inner dia of the outer conduit and dia of the inner rod be 2.3. It is quite near when inner rod or pipe has 4 to 4.5 mm outer dia and copper conduit has 10 mm inner dia. The exact equation of Impedance versus Diameter ratio is:

Z = 138 * Log(D/d)
The table of Impedance and Diameter Ratio
D = inner diameter of the tube
d = outer dia of the rod
Z = impedance in free air D / d Z / Ohm
2.2 47.3
2.3 50
2.4 52.5
2.5 54.9


If the inner wire is made from rod it is good idea to drill axially a 3 mm hole on the end of it so the rod can be solder firmly to the inner tap of the N connector. The length of the rod becomes about L/4, but it is better first to leave it longer and cut it later after the parts are first pre-assembled.

The copper conduit must be split with a metal saw as accurately as possible and deburred with a file. The end of the split conduit is then fastened to the centre of the pan. It is not possible to solder it directly to aluminium but we made a flange from tinned steel sheet to same dimensions as the flange of the N connector. In the middle of the flange is drilled a hole equal the outer dia of the conduit and four 3.5 mm holes as in the N connector. The one end of the split conduit is then soldered in the centre hole of the flange while keeping the width of the slots between halves to 1-1.5 mm.

The split conduit is then cut so that the length of the open slots becomes a very accurate L/4. This is the most accurate point in the antenna construction. Among with many roles, the slot acts as a band pass filter which rejects other frequencies than nominal HF.

Now is good time to pre-assemble parts. With four 3 mm screws, the N connector with the centre rod and the flange with split conduit are assembled on opposite sides of the centre hole of the pan, N connector to the outer side. The centre rod is now cut to same length as the split conduit.

The Dipole was made from 2 mm enamelled wire. The one arm of the dipole is soldered both to the centre rod and to the half of the copper conduit. The second arm of the dipole is soldered only to the second half of the conduit. The arms of the dipole are cut to L/4 from axle, so total width of the dipole becomes L/2.
Before soldering it is good idea to file grooves for dipole wire to the centre rod and the halves of the conduit.

To the right of the dipole there is the disc and the wire ring which can be assembled to the cover bulb so that their distance from dipole becomes to L/4.

The cover bulb can be locked with three 3 mm screws and sealed with silicone mass as well as the N connector joint.

On the very lowest point of the pan there must be drilled a small hole for condensed water exhaust.



Frequently asked details



The most important dimension of the antenna is the length of the slot,
which must be 31 mm @2.45 GHz.
I don't know the optimum width of the slot. I made it with metal handsaw inserting two blades parallel. So it becomes ca. 1.5 mm.






Yes really!

The one arm of the dipole is soldered both to the centre rod (2) and to the half of the copper conduit (1). The second arm of the dipole is soldered only to the second half of the conduit (3).

It doesn't mean a "short circuit". Remember the signal here is not direct current but high frequency !

See: Special Cases of Quarter Wavelength









Mast mounting of the antenna


Mast fasteners can be made from exhaust pipe clamps. See above some mounting ideas. Be careful not to mount clamps in the centre line otherwise the mast prevents connection of cable to the N connector. The rightmost picture is from back side.

Lightning protection

When the antenna is mounted above the roof there becomes a risk of lightning damage to the WLAN card.

The mast has to be grounded firmly e.g with 16 mm2 copper rope to a good earthing point. Lightning protection module is recommended between antenna cable at the place where the cable enters the roof.

Antenna cable and connectors

Cable type Belden H1000 is found to be low loss on microwave band and it is not very expensive. All cable and connector impedances must be 50 ohm. Outdoor connections are not watertight enough as such. So called self vulcanizing tape is best choice to wind over connection and above all there have to be wound black electrical tape to protect the vulcanizing tape against ultraviolet light. See cabling details .

Sources

Antenna construction is from page http://6mt.com/2304tech.htm where is found an item MICROWAVE ANTENNA YOU CAN BUILD (73 10-82) c56.zip . I have dimensioned it to 2.4 GHz band and made some additions.


11 July 2001

Martti Palomaki
Ilmajoki, Finland



Main wlan antenna page

A 2.4Ghz Vertical Collinear

A 2.4Ghz Vertical Collinear
Antenna for 802.11 Applications


By Brian Oblivion and Capt.Kaboom
modified by Richard A Wenner

Introduction

The collinear antenna was historically used by base station sites, stacking various 1/2 wave dipole elements on top of each other for increased gain connected by some equipment to correct for phase error between the elements of the array. The higher in frequency the better in gain you can achieve in a relatively small assembly. The eight element array built here will yield 6dBi gain in a radome of less than a meter.

There are 3 main sections to this antenna. Starting from bottom to top of the antenna, they are the RF connector/decoupler section, the elemental array section, and the quarter-wave whip section at the top of the unit.

Equipment and Materials Needed

Components:

2 meters LMR-400
2 12" length of 5/16 K&S brass tubing
1 12" length of 11/32 K&S brass tubing
1 block of wood of at least (3.52ft) 1m long
4 1" x 2" scrap wood blocks (or approximates)
1 1/64th (2mm) thick piece of scrap metal
1 brass toilet overflow tube ( EXACT DIMENSIONS NEEDED)
1 US Quarter (or brass disk of equivalent measurements)
solder (non-acid core plumbing solder)
flux paste

Tools:

Required:
---------
utility knife
hacksaw
High-wattage soldering gun (>260Watt)
metal ruler (Metric/English)
metal sandpaper
metal file (s)

Would make life MUCH easier:
----------------------------
hand-held pipe cutter
rotary coax cutter
vise (small)
micrometer (optional)
'Dremel' tool with metal grinding/cutting heads or metal grinder


Calculations

First determine how much gain you would like the antenna to have. This will determine how many elements you will need to construct. Choose from the following table:



Gain Number of Length of
in dB elements Antenna (cm)

--------------------------------------------------------------------------------

3.5 4 32
6 8 56
9 18 116
10 21 134


For our initial experimentation we decided to build the 8 element 6dB gain antenna.

We chose LMR-400 as it was lying on the floor the night we decided to construct the antenna. LMR-400 coax has a velocity factor of %85, mostly due to it's semi-rigidness and foam dielectric. LMR-200 would be the ideal choice, as it has a smaller diameter dielectric, thus requiring a smaller diameter brass tubing. This makes sense, as the max ERP out for 802.11 is under 1W.

The antenna is designed to optimally operate at the center of the 802.11 2.4GHz band. The center of the band is determined by the following:


802.11 frequency range: 2.4000GHz to 2.4835


low_freq - high_freq
center freq = ------------------------
2


2.4000 - 2.4835
center freq = ------------------------
2


center freq = 2.441GHz


The center operating frequency is then used in the following formula to determine the length of the individual antenna segments:


( c / fc )
segment length = ------------------------ * Vo
2

Where: c = speed of light in metres per second
fc = center freq.
Vo = velocity of coax

In our example:

c = 300000
fc = 2441000000
Vo = .85

( 300000 / 2441000000 )
segment length = -------------------------------------- * .85
2

segment length = 52.2 mm

NOTE: This is the length of the antenna segments. The actual brass elements are 8mm shorter than this number, to account for the antenna segment spacing. (See diagram below).



Measurements



Figure 1. Antenna segment measurements.


The schematic of the electrical components of the antenna is displayed in Figure 2. Note: this schematic is for an eight element collinear array. The 1/2 wavelength and 1/4 wavelength measurements calculated above are to be applied to the various elements in this schematic.




Figure 2. Electrical schematic of the collinear array.


Construction

We found that it was easier to cut coax and brass in batches, as you don't have to constantly adjust the micrometer.

Coax Preparation:

Coax length should be calculated in the following way:


coax length = 1/2 wavelength + 15mm


For coax: If you are not using a micrometer, but have access to a vise, mark the proper length (67.2mm) of the coax on the vise with a piece of tape. Align the "cut" end of the coax with the measurement indicated by the tape on the vise. The end of the vise is where you make the cut. (see how it's done). It may be easier to mark multiple sections for later cutting in a batch process.


Use the coax cutter or a 'Stanley' knife to cut the marked sections, and out


and strip away the cladding,

braid



and the foil.
Remove 10mm of cladding from each side the coax segment.

Set aside and prepare the rest of the segments.

Don't forget that the final element of the array is a 1/4 wave element. Cut a segment of coax to fit the 1/4 wave element as well.






Mark off first 44.2mm segment of the 5/16" brass tubing. Using a circular pipe cutter, set the wheel of the cutter on the side of the mark to make the element a bit longer than the 44.2mm measurement. Cut the brass by moving the cutter in a circular motion around the brass tubing, slightly tightening the wheel with every three or four revolutions. Repeat until all uncut 5/16" brass tubing is exhausted.

Again, don't forget about the final 1/4 wave element! Cut a length of brass accordingly.

Element assembly:

Pair up each of the brass tubing and coax segments.



The 5/16" brass tubing fits snuggly over the LMR-400 foam dielectric. Slip a brass element over each coax segment. Slowly twist the brass tubing as you pass it over the dielectric, until it is in place with an equal amount of exposed dielectric on each side of the tubing, as below.









Figure X: Diagram of completed element assembly.

If you think you have the dexterity to solder the elements without the use of a jig, or you plan on only making one or two of these antenna's, then skip the Jig construction and jump ahead directly to the element soldering section.

Jig Construction:

Constructing a jig will help with the construction of the antenna.



Even when not building multiples, the jig really helps when trying to solder the individual elements together.

Our jig was constructed out of 5ft long 1x2 inch scrap pine wood. a section of the wood was cut to make the four guiding posts used to "hold" the antenna elements in place when soldering together. You will need 10 nails and some scrap metal approx 1/16th thick (same thickness of the brass tubing). Metal PC slot fillers work well, and can be filed down to the proper width. Please refer to Figure 2 and 3 while reading the assembly instructions for visual assistance.


Step 1: Obtain a 5 foot long 1x2 inch scrap pine wood, 10 finishing
nails and 1 PC expansion card slot filler.

Step 2: Cut a 1 inch section off of the end of the 1x2 board,
resulting in a 1x1x2 piece of wood.

Step 3: Cut the 1x1x2 wood into 4 separate equal pieces.

Step 4: Drill two holes into each of the 4 wood pieces to
accommodate the finishing nails. Make sure the hole you
drill is not too large, as we only want to avoid splitting
the wood when driving in the nails.

Step 5: Cut away the excess metal from the PC expansion slot
filler, leaving a two inch long piece of metal. File away
one side (or a little of both) to 8mm, and drill two holes
into the metal to accommodate two finishing nails. These
nails will be used to attach the metal to the large piece
of wood.

Step 6: Attach the piece of metal 3 1/4 inches from one end of the
large piece of wood.




Step 7: Arrange two of the antenna elements in the jig. Use this as
a guide for where to attach the wood blocks to the large
piece of wood.

That's it!


Element soldering:

Element soldering is pretty straight forward. Don't dink around with little 8 US dollar soldering irons for this. You need a high-wattage soldering gun for this job. Spend the $30, it is a worthy investment, and purchase the proper tool for the job. If you built the jig, follow the instructions in Step 7 of the proceeding section. See how easy it is to do it in the jig? If not, then you'll be performing a balancing act, and I hope you have a steady hand.




When soldering the final element(1/4 wave element), remember that the center conductor is bent over and soldered to it's own brass tubing. When completed, it should look like below.







Note: Be careful when applying the heat to the brass elements. It doesn't take much time to generate enough heat to begin to melt the foam dielectric.

Solder all the elements at this point before proceeding to the next section. This is what your element array should look like.




Quarter Wave Whip Assembly:

The 1/4 wave whip assembly slides over the end of the last element of the antenna. See Figure 4 for exact measurements. Because the center conductor of the last element is soldered to the elements brass tubing, the top of the bend of the center conductor will be an arbitrary length unique to each antenna. The important thing here is for the top of the whip to be 1/4 wave in length from the end of the foam dielectric of the last element. Line up the 1/4 wave next to the last element and determine the length the notch will need to be.



Figure 4: Quarter Wave Whip Measurements and position

Cut out the notch to accommodate the soldered center conductor of the last element. If you are really slummin', use a hacksaw and file to make the notch. After the notch is cut and burrs are filed away mount the 1/4 wave whip on the end of the last element.




Decoupling and RF Connector Assembly:

The decoupling section is a bit involved, as it requires drilling a hole into a US Quarter, or similarly sized slug, and using a propane torch to solder it to the decoupling brass tubing.

There are two parts to this assembly. First, there is the feed-line element, constructed in the same manner as the antenna elements. Second, is the decoupling sleeve, mounted over the feed-line element.

The decoupler sleeve is constructed out of 1" brass tubing equal to 1/4 wavelength, a length of 11/32" brass tubing at least 1/4 wavelength, and 1 US Quarter with a center-drilled hole to accommodate the 11/32" brass tubing.



Above is picture of the 1/4 wavelength 1" brass tubing with the 11/32" brass tubing soldered into the center of the US quarter along side. Below is the fully assembled unit from the top and bottom







Figure X. Diagram of decoupling sleeve

The feed-line is similar in construction to the antenna elements. The difference is the coax is of much longer length than the 5/16" brass tubing. The coax is prepared in a much different fashion since we solder the braid of the coax to the end of the brass tubing 1/4 wavelength up from the end of the N connector. Below this, the cladding remains intact and terminates in the N connector assembly. The brass tubing must be cut so that at least 1/2 wavelength of 5/16 brass tubing is between the end of the decoupler sleeve assembly and the 1st antenna element (see diagram). It must also accommodate the length of the decoupler sleeve assembly plus allowing a length for tuning of the sleeve to the feed-line (this is done my sliding the sleeve up and down over the feed-line tubing). In our example, the coax was 10.8cm(4 1/4"), and the 5/16" brass tubing was 6.8cm (2 11/16"), in length.

When completed it should look like this:-



As part of the final assembly it looked like this:-




Tuning and final assembly

Tuning:

Unfortunately, without a spectrum analyzer or SWR/Power meter one cannot optimally tune the antenna, but one can coarsely tune it using the Linux wireless tools and two wireless NIC's. By adjusting the decoupling sleeve, you will notice a change in the RSSI reading as you slide the decoupling along the feed-line element. Adjust until you reach a peak in the RSSI in the receiver. Only take measurements when not touching the antenna, and always return to a similar position when taking a reading. Your body changes the RF characteristics of the room you are working in. Once the antenna has been properly matched, fix the decoupler in place with a bead of solder and proceed to the next section.

Radome construction:

Outdoor electrical UV resistant conduit was used for the radome. It was cut to the appropriate length to accommodate the entire array, leaving the female N connector hang out the bottom by 1/2 inch. The array is held in place with plumbers epoxy. We used a PVC cap to cover the top, but it could have been sealed with plumbers epoxy as well. Using double sided sticky tape, the array is held in place at two locations within the tube.




Figure X: diagram of finished antenna in radome.

Good luck!

Tuesday, July 10, 2007

The open-access debate over spectrum

The open-access debate over spectrum
Why not let public safety and commercial operators share the same band?
Craig Mathias Today’s Top Stories or Other Wireless Networking Stories
Comments (0) Recommendations: 79 — Recommend this article


Securing the Enterprise Infrastructure from Wireless Threats
How to be a Network Builder, Problem Solver and a Business Driver - in half the time!
Secure Email Trial Download

Managing the Mobile Enterprise
A guide for creating effective enterprise Wireless Strategies
Frost & Sullivan assesses the ROI of Treo™smartphones in the enterprise.
Good Mobile Messaging

The Untethered Worker
Strategies for Protecting Against Internet Threats
A Great Leap Forward in Storage for the SMB

Sign up to receive Security Resource Alerts



June 19, 2007 (Computerworld) -- If you've been following the developments surrounding the upcoming 700-MHz auctions, you've probably heard the term "open access" by now.




Like 4G (which I'll return to shortly), open access is a somewhat imprecise term, but I'm using it here to refer to a network that is capable of supporting multiple classes of service simultaneously via a common set of protocols. With respect to the latter, that would be IP, the only networking protocol that matters anymore. The benefits of the open-access approach are significant and far-reaching, and they have led me to conclude that this is the only way we should be building commercial and public-safety networks going forward.


Why is this important? Well, spectrum is a scarce, expensive commodity thanks to the laws of physics and the auction process that is used to allocate licensed spectrum in most parts of the industrialized world today. The laws of physics are a problem because propagation characteristics vary with frequency -- higher frequencies are more directional and don't usually penetrate buildings very well. This means that only a very limited amount of spectrum is suitable for mobile communications. The auction process makes this limited spectrum expensive, with the auctions cleverly designed to raise the maximum amount of money for the U.S. Treasury.


OK, so spectrum is scarce and expensive and some of the best of this will shortly be going on the block as the FCC starts auctioning the 700-MHz bands. This spectrum is right below the 800-MHz bands used for cellular and public safety, and public safety (along with commercial interests with really, really deep pockets) is going to be a big recipient of spectrum under the proposed rules.


But wait just a minute: Why not build a single, open-access network that can meet the needs of both the commercial world and public safety, simultaneously? That's right, both in one service. Heresy!


Traditionally, blocks of spectrum have been exclusively reserved for public safety because that's historically how it's been done. And the technology of the day -- analog push-to-talk radio -- basically required reserved spectrum. This is wasteful, when you think about it. Much public-safety spectrum is unused much of the time and isn't available to anyone else. But modern digital communications technology, based on IP, allows for prioritizing traffic, at least within a single network.

Continued...
1 | 2 | NEXT



Recommendations: 79 — Recommend this article


Print this Story Send Us Feedback E-mail this Story Digg this Story Slashdot this Story

Tune in to wireless video

Tune in to wireless video
New technologies are sprouting up to offer more options for wireless TV
Craig Mathias Today’s Top Stories or Other Wireless Networking Stories
Comments (2) Recommendations: 42 — Recommend this article


Securing the Enterprise Infrastructure from Wireless Threats
How to be a Network Builder, Problem Solver and a Business Driver - in half the time!
Secure Email Trial Download

Managing the Mobile Enterprise
A guide for creating effective enterprise Wireless Strategies
Frost & Sullivan assesses the ROI of Treo™smartphones in the enterprise.
Good Mobile Messaging

The Untethered Worker
Strategies for Protecting Against Internet Threats
A Great Leap Forward in Storage for the SMB

Sign up to receive Security Resource Alerts



June 26, 2007 (Computerworld) -- Video, whether wireless or not, isn't usually considered important in enterprise environments. And, despite a lot of discussion about using wireless to distribute broadcast/cable/satellite video in the home, it isn't all that common yet either.


But I think video is going to become a lot more important. With respect to wireless WANs, for example, many cellular carriers have at least some form of video-entertainment service for sale. Video has the highest potential information content of any medium in common use today. And, from a wireless networking perspective, doing a good job with video usually means doing a good job with any other form of traffic.


Video is, after all, the worst of both worlds -- it has lots of large data objects, and, in the case of streaming video, it's time-bounded. Headroom is important, and wireless networks aren't known for having headroom to spare.


For today, I want to focus just on video distribution in the home, but the tools and techniques being developed here will find their way, over time, into corporate video applications. Residential video is obviously a huge market opportunity. People still watch TV even though, with 500 channels to choose from, there is never anything good on. Regardless, the TV is usually located nowhere near the cable supplying the video. There's also an increasing interest in being able to watch TV while mobile. For example, I connect my SlingBox to one of the six WLANs in my house (if radio really does cause cancer, I'm a goner), and watch it on PCs everywhere, even outside.


While I mostly use MIMO-based Wi-Fi, there's an intensifying debate over what the best wireless technology for video is. I recently spent some time on the phone with ultrawideband (UWB) chip builder Tzero Technologies Inc., which is focusing on video distribution within the home. UWB has the advantage of having a lot of potential bandwidth available -- up to 7.5 GHz. in the U.S., although much less than that is required, even for uncompressed video. The High Definition Multimedia Interface(HDMI) only requires 1.5 Gbit/sec. for 720p HDTV video, and about double that for 1080p. Tzero believes, consequently, that UWB is ideal for HDTV-class video distribution, and there are a few other UWB companies also producing video-oriented products.

Continued...
1 | 2 | NEXT



Recommendations: 42 — Recommend this article

MAKE FREE MONEY

WELCOME

Welcome to my world where everybody is somebody and none is nobody. Together we shall hack all hackables