Manual SPECTRAN V5
© Aaronia AG 2016 | www.aaronia.com
37
PHYSICAL UNITS
7.3. Calculating the wavelength in [m]
To calculate the wavelength from the frequency, use the following formula:
Here,
c
corresponds to the speed of light in
(rounded to 300,000km/s in
our example), „f“ to the frequency of the radiation in [Hz], and λ to the wave
-
length in [m]. Examples:
(For 900 MHz, the result is 0.33m)
(For 1 800 MHz, the result is 0.17 m)
(For 2 GHz, the result is 0.15 m)
Further information concerning wavelength is contained in table 4.
7.4. Calculating the „close-up range“ in [m]
If you want to perform a measurement, you need to do this outside of the so
called close-up range of the transmitter. The close-up range depends on the
transmitter frequency. According to the aforementioned formula, the closeup-
range can be determined quickly. Here, you simply need to multiply the result
-
ing wavelength by a factor of 10 (there are some sources which only use a
factor of 3). The result is the close-up range, i. e. the minimum distance to the
transmitter in which a realistic and sensible measurement can be achieved.
Example: For a „900MHz cell phone“ the wavelength is:
Hence, the close-up range is 0.33m * 10 = 3.3m.
It is easy to see, that e. g. measurements taken directly next to the cell phone
will definitely result in wrong readings.
