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Contents:
Intel® Wireless Modem: Signal Information - Hints And Tips
Hints and Tips on getting a usable signal:
Intel® Wireless Modems (IWMs) are radio devices which require a usable signal to work properly. The presence of a signal is important, the strength of the signal is not. A usable signal is present when the 'SERV' indicator appears in the lower left corner of the IWM's display. Therefore, as long as you can see the 'SERV' indicator, you can send and receive data.
If you can't get the 'SERV' indicator to show up, move the IWM to one of the following locations and then wait 10 to 30 seconds for the IWM to try to establish contact with a base station.
- Try moving closer to a window. Radio signals travel through windows better than walls.
- Try moving the IWM to the left or to the right about 12 inches (length of an IWM radio wave). A signal might be blocked on one side of your computer, but clear on the other.
- Try moving higher or placing the IWM in an elevated position. The higher you go, the better your chance of getting into the line of sight of the base station.
If none of the above works, you may need a high-gain antenna.
Intel® Wireless Modem: Signal Information - General
IWMs are radio transceivers, which use radio technology to transmit and receive information. While IWMs offer freedom from connectivity restrictions such as the need to connect to phone lines, IWMs can be susceptible to all the problems associated with radio wave transmission.
IWMs were designed with the pitfalls of radio in mind. IWMs have internal circuitry and buffers to handle momentary lapses in the signal so they are resistant to interference by sun spots and other sources. IWMs work on very specific frequencies to limit the interference they cause with other electronic devices, and the ability of other electronic devices to interfere with them. Additionally, IWMs use special modulation (GMSK modulation) of the signals to further ensure signal integrity. Only signals matching the GMSK modulation are processed; all others are rejected.
IWMs transmit at frequencies from 896MHz to 901MHz and receive at frequencies from 935MHz to 940MHz. The wavelengths for these frequencies range from 12.6 to 13.2 inches (31.9 to 33.4 cm), allowing the standard antenna to be quite short and enhance the IWM's portability. Internally, the antenna is folded over on itself, so it appears shorter than the wavelength of the signal.
As with all radios, the strength of a usable signal detected by an IWM is determined by several factors, the most important being proximity to the transmission site. IWMs use signals broadcast by base stations set up throughout the United States. Any time an IWM gets a usable signal from a base station, the 'SERV' indicator shows up on the display of the IWM. This 'SERV' indicator shows that the IWM and the base station have established a reliable communication link and the IWM can send and receive signals.
The 'SIGN' indicator on the display simply shows the strength of the signal received by the IWM, not how well or how poorly the IWM can communicate with the base station. The 'SIGN' indicator has nothing to do with the IWM's ability to send and receive signals. The only important indicator is the 'SERV' indicator. Intel® Wireless Modem: Signal Information - About Reception
Proximity to a base station is the single biggest factor in determining whether or not the IWM can successfully send and receive signals. The closer an IWM is to a base station, the more likely the signals broadcast from the base station are going to reach the IWM's antenna.
A very simple rule of thumb for signal strength vs. distance from the base station is:
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Distance4 |
(or, one over Distance to the fourth power.)
To illustrate, suppose there are two locations, A and B, at different distances from the base station. If Location B is twice as far from the base station as Location A, the signal strength at Location B will be 1/16th of the signal strength at Location A (2x2x2x2 = 16). An IWM can successfully communicate with base stations up to 10 miles away (under extremely good conditions).
The second most important factor in the IWM's ability to receive a usable signal is the number of obstacles between the IWM and the base station. Radio waves cannot penetrate solid objects such as mountains, thick concrete, and metal. Radio waves can penetrate windows to a certain degree. Radio waves travel line of sight, meaning they don't go into valleys and canyons unless the base station is high enough to "see" down into the valley. Radio waves can be deflected and stopped by leaves on trees, too, so you might have a great signal in December, but no signal at all in April.
Another potential problem for radio technology is "dead zones," areas in which the radio waves just don't seem to exist. The most likely cause of a dead zone (besides being out of the line of sight of the base station) is reflection of the radio signal. For example, the base station may be on one side of the IWM and a large surface that reflects radio signals (such as a building) may be on the other side. The radio signal is reflected by the building and reaches the IWM at almost the same time that the signal from the base station reaches the IWM. The direct and reflected signals cancel each other out.
This applies to:
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