Family Software Newsletter #32 - December 17, 2006

Drag Racing Computers and Software - www.iFamilySoftware.com

Topics

1. The Truth About Paging Systems

-- The Truth About Paging Systems --

Power- The Watts Question
Many companies will say that more power (wattage or watts) into a system means the system works better over a longer distance. To better understand the "watts question," one must understand the difference between the power into a transmitter and the power out (radiated power). The power into the transmitter is the number salespeople often use to sell their product. However, the radiated effective power from the transmitter's antenna is the power that counts. The FCC strictly regulates the amount of power radiated by the antenna. No legal wireless system can radiate more power than the FCC allows. For a non-licensed channel, this is a maximum of 2 watts of output power. The internal design of the transmitter determines how well the transmitter converts input power into output power. To further complicate the "watts question," all radiated power is not necessarily useful power. Many "cheap" designs radiate a lot of power, but the power is distributed over several frequencies to which the receiver (pager) is not listening. The "useful energy" would be that energy that is on the correct frequency for the system. To radiate power most efficiently, a transmitter should have an antenna that is ¼ or ½ wavelength of the frequency. Thus, the antenna length is an important factor as discussed in the frequency portion of this article. We have discovered a vast difference between transmitter designs, both in power efficiency and in useful radiated energy.

Receiver Sensitivity
Vibrating pager receivers vary in their signal sensitivity. Receiver sensitivity could be compared to a person's ability to hear. Well-designed receivers are able to discern messages at energy levels far below what less sensitive receivers are able to pick up. In technical terms, receivers can be broad band lower gain or narrow band higher gain by design. The FCC does not regulate the efficiency or sensitivity of receivers; they only regulate the maximum spurious radiation coming from the pagers as a result of the electronic circuits inside. Receiver sensitivity alone can easily be responsible for causing one system to work twice as far as another.

System Frequency
Finally, the third factor to consider when calculating the range of a wireless system is frequency. There are different frequencies on which the systems operate. Currently there are two groups of systems: those operating at 27 MHz and those operating in the 450 MHz to 470 MHz range (UHF). The FCC has different power output rules for the two groups. The only legal systems that radiate 7 watts from the output stage are 27.255 MHz transmitters, also known as the Citizens Band Channel 23. As described earlier, to effectively radiate this power from an antenna, the antenna should be at least ¼ wavelength long. However, ¼ wavelength at 27 MHz is 8 feet. Remember that both the transmitter and the receiver need an antenna. None of the 27 MHz systems have 8-foot antennas as this would be impractical. All manufacturers compromise the antenna design to fit in a smaller package using various forms of antenna loading, which affects the efficiency of the transmitter and the receiver. We have found the range of the 27 MHz we have tested to be less than the UHF systems. Generally the longer-range pagers are UHF systems. The UHF systems operate in the 450 to 470 MHz range. They all have approximately 2 watts applied to the output stage that radiates the power to the vibrating pagers. The FCC controls, licenses, and limits the amount of radiated power from transmitters. A ¼ wavelength antenna for a 450 MHz system is approximately 6.5 inches. Even on these systems, designers use some antenna loading, but they tend to radiate power much more efficiently because the antennas are closer to the ideal length. In addition to the above considerations, there are many theoretical equations that govern the propagation of radio frequency energy through air and through materials. The Scope UHF system is the best designed and most efficient system we have ever seen. Our engineers have tested several UHF systems from other companies and have never found one that compares to the Scope system.

Our Scope Paging System will broadcast cleanly for up to a five (5) mile radius with our external dipole (1/2 wave) antenna and at least a one (1) mile radius with the standard (1/4 wave) antenna. I've seen some of the others that will not transmit cleanly at Englishtown, NJ, for even a 1/2 mile to the staging lanes. So much for false advertising claims concerning wattage!

-- REAL World Technical Support --
With Family Software, you'll get better technical support than anywhere on the planet. Why? Because, we design and/or use all of the products that we sell. All of my 35+ years of on-track racing experience and knowledge is available to you. Try to find that kind of information at any one of our competitors. You won't be able to, I guarantee it! Family Software cares about the racer and his/her success as a racer. We also want you to get the most value for your hard earned dollars.

-- Secure Ordering --
You can safely order directly from our web site. All of your information is handled on our Secure Server. We have established a privacy policy and it is posted on the web site. Our company is registered with the Public Eye for safe, secure ordering.

Bob Kodadek
SC 1596
Family Software - Drag Racing Computers and Software
http://www.iFamilySoftware.com - 610.497.5561(Voice/Fax)

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