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KF5JRV > TECH 11.11.16 14:36l 50 Lines 2789 Bytes #-3225 (0) @ WW
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NIST radio station WWV broadcasts time and frequency information 24 hours per day, 7 days per week to millions of listeners wor
ldwide. WWV is located in Fort Collins, Colorado, about 100 kilometers north of Denver. The broadcast information includes time
announcements, standard time intervals, standard frequencies, UT1 time corrections, a BCD time code, geophysical alerts and ma
rine storm warnings.
Broadcast Frequencies
WWV operates in the high frequency (HF) portion of the radio spectrum. The station radiates 10,000 W on 5, 10, and 15 MHz; and
2500 W on 2.5 and 20 MHz. Each frequency is broadcast from a separate transmitter. Although each frequency carries the same inf
ormation, multiple frequencies are used because the quality of HF reception depends on many factors such as location, time of y
ear, time of day, the frequency being used, and atmospheric and ionospheric propagation conditions. The variety of frequencies
makes it likely that at least one frequency will be usable at all times.
Antennas
The WWV antennas are half-wave vertical antennas that radiate omnidirectional patterns.
There are actually five antennas at the station site, one for each frequency. Each antenna is connected to a single transmitter
using a rigid coaxial line, and the site is designed so that no two coaxial lines cross. Each antenna is mounted on a tower th
at is approximately one half-wavelength tall. The tallest tower, for 2.5 MHz, is about 60 m tall. The shortest tower, for 20 MH
z, is about 7.5 m tall. The top half of each antenna is a quarter-wavelength radiating element. The bottom half of each antenna
consists of nine quarter-wavelength wires that connect to the center of the tower and slope downwards to the ground at a 45 de
gree angle. This sloping skirt functions as the lower half of the radiating system and also guys the antenna.
WWV Antenna Coordinates
Frequency (MHz) Latitude Longitude
2.5 40ø 40' 55.2" N 105ø 02' 31.3" W
5 40ø 40' 42.1" N 105ø 02' 24.9" W
10 40ø 40' 47.8" N 105ø 02' 25.1" W
15 40ø 40' 45.0" N 105ø 02' 24.5" W
20 40ø 40' 53.1" N 105ø 02' 28.5" W
Modulation
The signals broadcast by WWV use double sideband amplitude modu-lation. The modulation level is 50 percent for the steady tones
, 50 percent for the BCD time code, 100 percent for the second pulses and the minute and hour markers, and 75 percent for the v
oice announcements.
73 Scott KF5JRV
KF5JRV.#NWAR.AR.USA.NA
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