About Wireless Security Cameras and Wireless Transmitters


What is a Wireless Camera?

Wireless Security Cameras are just standard cameras that have a built-in transmitter and antenna. When power is applied the cameras' video (and audio is so equipped) is sent wirelessly by radio waves to a receiver. It should be noted that even a wireless camera will need power either in the form of a battery or power supply plugged into a standard electrical outlet. So the term wireless is not totally correct since it just means you do not need to run a video or audio cable from the camera to the receiver. The receiver as its name implies will receive this radio wave signal and turn it back into a standard composite video signal that will then be plugged into a monitor (which could be a standard TV) or some form of recording device like a digital video recorder.

How Far Can Wireless Signals Transmit?

The range of the signals is usually stated based on line of sight. True line of sight means more than just the antenna of the transmitter can see the antenna of the receiver. The wireless signals using the standard omni-directional antennas will need about a 30 ft. diameter clearing between antennas for maximum range. So to get the maximum distance the transmitter and receiver antennas will need to be at least 15 feet off the ground otherwise the ground itself will attenuate the signal. This doesn't mean that the transmitter or receiver can't be on a 3 feet high shelf in your house but the lower it is placed and the more obstructions such as trees, bushes and buildings the less distance you can achieve. Metal and concrete are the hardest for the signals to penetrate. Through normal house construction of wood and drywall you will probably loose 15 to 20% through each wall the signal must pass for 2.4 GHz equipment.

What Can be Done to Get More Distance?

If you find you are getting a signal but it has lines or fades in and out try placing the receiver by a window or closer to an exterior wall and run a cable to your monitor or recording device. Also if your receiver has a detachable antenna you can buy extension cable and mount the antenna outside your building and run the cable through a hole much like is done for cable TV or through a window. This will eliminate the walls giving you better line of sight and greater signal distance. To keep signal loss at a minimum the shorter the antenna cable the better try not to exceed 15 to 25 feet. Greater signal distance can also be achieved by the use of high gain directional antennas. The antennas that normally come with most wireless cameras are omni-directional which are good for receiving signals from any direction. By using a high gain directional antenna the signal distance can be doubled or more depending on the dB gain. The drawback is that the antennas are larger, more expensive and must be pointed directly at each other and on the same axis (horizontal, vertical). However if wireless is the only way to get the signal the extra cost and size may be worth the investment.

Another factor that will affect distance is the frequency of the transmitter. The lower the frequency the greater penetrating ability. It is similar to standing outside a house or car with a stereo on, you can more easily hear the drum or bass sounds than the other instruments. For true line of sight with analog transmitters of the same power or amplitude signal the lower frequency will still have greater signal distance using the standard dipole antennas. However the newer digital transmitters like our PD2410 and PD2420 do not send video in a continuous signal but rather their digital signal consists of data that is discrete or separate, as opposed to continuous; which from our testing transmits further than analog signals of the same power. When needing longer distance using high gain antennas the higher frequencies have the advantage of more gain from the same size antenna making 2.4 GHz better for long range high gain antenna situations. Another factor to consider is the bandwidth is smaller in the lower frequencies limiting the number of channels that can be use in one location.

Will Other Wireless Devices Interfere with the Cameras?

When using wireless cameras that operate in the 2.4 GHz range there can be interference problems from devices such as cordless phones, wireless Internet routers and microwave ovens. Many devices like cordless phones and wireless routers allow you to select different frequencies for them to operate on that may not interfere with the cameras. Unfortunately anytime you have a number of devices operating wirelessly at the same time interference is possible. Another option that can help is to use directional antennas on both the transmitter and receiver since their signals are then confined to a smaller area directly between them. The 900 MHz and 1.2 GHz signals are less prone to interference since most common wireless devices in use today do not operate at those frequencies.

Can I Make Any Camera Wireless?

Many times its hard to find the right camera that is also wireless with a built-in transmitter. For these situations you may want to consider using a separate transmitter and receiver set. The advantage is that you can use any camera so you can and plug it into a transmitter to make it wireless. This allows you to choose just the right camera and if your needs change in the future you can just plug a different camera into the transmitter. If the cameras you want to use will be located outside most transmitters are not weatherproof on there own. There are a couple of ways to still use them outside, one is to place the transmitter next to the camera in a weatherproof enclosure with the antenna sticking out for best performance. The second way is to place the camera where you want it such as on the front of you house and the transmitter in your garage or an enclosed porch. Then run a video/power cable to the camera from an outlet in the garage, it provides the needed power to the camera and brings the video back to the transmitter. From there the transmitter will send the signal wirelessly to the receiver located inside.