Cordless Phone Information
This information section is for all cordless (but not cellular) phones. The information is provided as an effort to offer various ways of improving efficiency and to explain certain operating characteristics of these types of telephones. You may also find useful information on one of our telephone frequency pages, 49 Mhz Cordless Phone Frequency Table and 900 Mhz Cordless Phone Frequency Information.
Antenna efficiency is one key factor that enables greater
range for the 900 MHz and 2.4 GHz phones. An antenna, base or handset, should be greater than one quarter wavelength in length for efficient radiation. At 46 MHz the antennas should be longer than five feet (about 60 inches or 1.5 meters), at 900 MHz the antenna length should be greater than 3 inches (8 cm) and at 2.4 GHz in should be about 1.5 inches (3 cm). As far as can be determined, there were never any 49 MHZ cordless phones with 5 foot antennae on them; most are about 6 inches. The antenna length
factor would benefit both analog and digital phones. Digital phones in the 900 MHz and 2.4 GHz bands that
use digital spread spectrum (DSS) techniques have an
additional range factor in their favor over analog phones in all 3 bands. The FCC allows DSS phones to transmit up
to one watt of power (though not all do) while analog phones are limited to one milliwatt (0.001 watt). This factor of one thousand times greater transmitter power is significant in enabling greater range claims for DSS systems which claim ranges up to a mile (1.6 km)depending on obstructions in the environment such as buildings and trees and atmospheric conditions. DSS phones can use direct sequence encoding or frequency hopping spread spectrum techniques. There are benefits and disadvantages in using each of these capabilities. The sources of noise interference in the user environment determine which of these techniques is superior in a practical sense. However, this is a much to complicated issue for a typical user to analyze except by trial and error. It is a prove fact though, trial and error works!
There are some industry claims that the microwave energy in the 900 MHz and 2.4 GHz phones bounce off building
materials better than 46 MHz phones do, thus redirecting waves and perhaps giving better range. However,
depending on the location, this factor could also
have a negative impact on the microwave phones. True or untrue, there is no argument that any sort of obstacle is detremental to the signal. Panasonic has taken what is as far as we know, a unique approach to the differences between frequency capabilities. They have designed a phone system that transmits at 2.4 GHz from the base station and transmits 900 MHz from the cordless phones. Is this the best of all worlds? The price is high and would suport a positive answer; however, it would probably be most useful in an electronic environment with a great deal of interference. This is a quote indicating Panasonic's opinion. (It should be noted that Panasonic has been a leader in this industry MANY times...)
The new Panasonic GigaRange Extreme cordless phones
will out-perform any cordless phone available today. In
fact, its range is 20 times greater than an ordinary
cordless phone, up to 8 times longer than a 900 MHz phone
and up to twice as far as 900MHz phones with Digital Spread Spectrum (DSS) technology. Ordinary cordless phones use 2 signals to transmit and receive (talk and listen) which operate on a single band. These two signals can interfere with one another. The Panasonic GigaRange phones actually use two different bands, one for sending and one for receiving. A 2.4 GHz signal is transmitted from the base to the handset, while the handset uses a 900 MHz signal back to the base. The result is true duplex (two-way conversation) sound with virtually no echo and greatly enhanced distance performance.
While we neither advocate or denounce Panasonic's claims, we do feel that this is the emerging technology and will be emulated by other manufacturers.