When the RC frequency spectrum was first introduced to provide controlled facilities for radio control (RC) modelers, it was limited to a set of just six. These frequencies were not labeled with channel numbers as they are today, but were represented by multi-colored flags; purple/white for 72.320 MHz (megahertz), red/white for 72.240 MHz, etc. Having only 6 frequencies to choose from was quite restrictive and meant a lot of RC airplane pilots had to be grounded, waiting to take their turn on a given frequency.

The RC model airplane frequency spectrum today is much broader, consisting of a much larger batch of 50 channels in the 72 MHz band in the USA, a similar batch in the 35Mhz band in the UK and other bands according to country. In addition, there remain a few 27 MHz channels shared across many uses including for ‘park flyer’ model airplanes, and a handful of other more specialized channels reserved for licensed amateur radio operators. For convenience, I’m just going to refer to the 72Mhz band as the band allocated for model airplane use in the USA. You will need to read that as the band allocated for model airplane use in your own country.

So now you’ve decided to buy your RC model and radio equipment you also need to decide which radio frequency you are going to operate on. Unlike most other features of the sport, choosing a popular channel which is used by lots of other people is not a good idea. Choosing a standard 72 MHz frequency for your radio can be as simple as going to the local hobby store and

purchasing one with a standard radio setup. But randomly choosing a channel can result in a problem if you don’t do a little investigation first.

Firstly, decide whether you are going to be a park flyer using 27 MHz or going for a more advanced setup on 72 MHz. The 27 MHz channels are primarily dedicated to what are considered “park flyers”. These pre-packaged systems usually come with everything you need to get up and flying and are intended for the casual flyer that just wants to get out, get in the air, and not mess with the higher cost of a more complex airplane and radio setup. Choosing a RC model airplane park flyer package with a pre-set frequency needs little to no investigation since you have little choice as the packages give you a choice of only 3 or 4 channels, some FM, some AM. Channel conflicts in a RC park flying situation are less common due to the large number of parks and flying areas available to the casual pilot. But if you do invest in a park flyer then be aware that there may well be other pilots out there in the park using the same frequency as you – and that can mean expensive trouble when you lose control of your airplane, or even worse if some stranger accuses you of causing his airplane to crash.

Second, if you are going for 72 MHz then visit your flying field and find out what other people are using. Imagine arriving to your favorite RC model airplane flying field only to find someone else already using the channel you have just paid out good money for. Some clubs have rules pertaining to what happens in this situation. As only one pilot can operate at a time on a given frequency this usually means pilots having to switch off and take turns using the frequency – and some means of the club controlling the changeover process either by physically taking control of the transmitter or just having a procedure written into the club rules. If you are flying at a busy site that is not a sanctioned flying club with rules and bylaws, you might find yourself sitting out and unable to fly for the day.

The smartest way to choose an RC frequency for your radio is to do some legwork first. Visit the field where you will do most of your flying. Investigate what channels are already in use and which channels are seldom used. Finding one that is infrequently used or not used at all will allow you to buy, secure in the nowledge that you will be able to fly with minimum interruption.

Third, make sure you can change the frequency after you have bought the equipment. If you take care to check before you buy whether the system will allow you to do a manual crystal replacement then if you run into a problem you can change later to a channel which is less busy. Some crystal changes you can do yourself while others have to go back to the factory to have the work done. Regardless of your current situation, if you already have an RC radio setup, or just thinking about getting one, doing a little footwork up front can go a long way.

Bluetooth Technology

What is Bluetooth?

Bluetooth technology is a type of the wireless technology that eliminates the need for the number of inconvenient cables and devices that are used to connect the computers, mobile phones, digital cameras, handheld devices and new digital appliances. Bluetooth enables the users to connect to a wide variety of telecommunication and computing devices easily, without cables.

It makes rapid ad hoc connections, automatic unconscious connections between two or more digital devices. Bluetooth provides the opportunity of using the mobile data in different applications. Bluetooth makes wireless communication between the two devices in a localized area of a room of office or home very easily. Bluetooth technology uses radio-based links and all the connections between the devices and invisible and instantaneous.

By Bluetooth technology your laptop can send print request to a printer in your next room. Bluetooth is actually a standard for wireless communication between the devices in a relatively small area and it is therefore works fine in the personal area network (PAN) using radio frequency.

Any two devices that follow the Bluetooth standard can communicate with each other. A number of the Bluetooth devices like digital camera, mobile phone and handheld pc can form a network. You can send emails to your mobile phones from your laptop without any physical connect between your laptop and your mobile phones.

Features of Bluetooth technology

• Bluetooth technology uses radio waves for communication in 2.4 GHz

• It supports multipoint communication not just point to point.

• Bluetooth works in a small area of 10-15 meters.

• Bluetooth offers speed of 1-2 Mbps.

• Bluetooth chipsets are less expensive though more expensive than IrDA.

How Bluetooth Technology Works

Bluetooth is a high speed wireless link technology that uses the radio waves. It is designed to connect the mobile phones, laptops, hand held devices and portable equipments with almost no work by the end users. Unlike infrared Bluetooth does not require line of sight between the connecting units. Bluetooth technology is a modified form of the current Wireless LAN technology and it’s more acceptable for its relative small size and low cost.

The current circuits are contained on a circuit board of 0.9 cm square and a much smaller single chip version is in development and soon it will be in use. The cost of the Bluetooth device is expected to fall rapidly. Bluetooth chip has to be equipped in many devices. In Bluetooth technology, small and inexpensive transceivers have been placed in the digital devices. The radio waves operate at 2.45 Ghz band on the Bluetooth devices. Bluetooth supports the data speed up to 721 Kbps and 3 voice channels. The Bluetooth chip can either be built into the devices or it can be uses as an adapter. In computer it can be used with the USB port. Each Bluetooth device has a 48 bit address from the IEEE 802 standards and the Bluetooth connections can be either point to point or multipoint. Bluetooth range is 10 meter but it can be extended up to 100 meters by increasing the power.

Bluetooth devices are protected from the external interference because they change their frequency up to 1600 times in a second. Bluetooth radio technology provides the bridge between the existing data network. Bluetooth guarantees security at the bit level and the authentication is controlled by the end user by using 128 bit key. An important face of the Bluetooth technology is that it instantly forms a network when two or more devices come closer in the range of each other.

Bluetooth Technology Benefits

Bluetooth technology is a convenient choice of communication in a wire free, short range environment. Bluetooth is a globally available standard for connecting the devices like mobile phones, digital cameras, laptops, MP3 Players, cars, stereo headsets etc. Bluetooth enable devices do not need to install any drivers. The key benefits of the Bluetooth wireless technology are its built-in-security, low cost, easy of use, robustness, and ad hoc networking capabilities.

The Bluetooth wireless technology is available globally. Many manufactures from the different companies are busy to implement the technology in their products. Bluetooth technology operates in the 2.4 Ghz, one of the unlicensed, industrial and scientific radio band. Bluetooth technology is a free of charge service but your mobile phones set should support the GSM and CDMA technology.

Today mobile phones have built in capabilities and Bluetooth functionalities in them. Bluetooth technology is available in the different range of the devices like mobile phones, automobiles, medical devices, industries and enterprises etc.

Due to the key features of the Bluetooth technology like low power consumption, low cost and wireless features make it more popular. Bluetooth technology does not require any fixed infrastructure and it is very simple to install and setup.

No wires are required to connect the Bluetooth devices. You can connect to other Bluetooth enabled devices anytime if they come in your range. Bluetooth wireless technology is widely supported and is secure wireless standard today. Bluetooth devices has built-in security features such as 128 bit encryption and pin code authentication when Bluetooth devices identify themselves they use the pin code when they first time connect.

Bushra Bashir

http://www.networktutorials.info