shows the WWVH signal and local synchronized time ticks superimposed.
Note that the nuclear-device pulse was also picked up on the WWVH re~
ceiver,
The specific second can be determined by counting WWVH second
marks with reference to the missing 59th mark. Time in minutes and
hours is noted from a chronometer synchronized with WWVH and the start
of the camera. Detonation time from the record shown in Figure 1 was
28 February 1844:59.9962Z; with corrections for propagation times of the
nuclear-device signal and WWVH, the time is 1845:00.011Z.
Standards Close-in Station. At the close-in
site, a vertical antenna 0.6 inch in diameter and 2 meters long was
used and located about 60 meters from the recording equipment in order
to minimize distortion due to radiation. At the base of the antenna a
cathode follower fed a coaxial line to the recording instruments which
consisted essentially of several oscilloscopes set at various sweep
speeds and gains.
At close distances (320 km) to ground zero, pulses
were strong (several volts per meter) so there was no concern with
interference from natural sources or transmitting stations.
Conse-
quently, the bandwidth of the pulses was limited only by the oscillo-
scopes. This limit was about 40 Me for one type of oscilloscope used
and about 13 Mc for the others. The low frequency limit was about 160
eps. A block diagram of the close~in waveform instrumentation is given
in Figure 3.
Distant Stations.
At distant points operated by NBS and the
Defense Research Laboratory (DRL), 30-foot vertical antennae with
standard cathode followers were used. Narrow-band (about 200 cps) and
broad-band (about 1 to 70 ke) recordings were made. A ground mat 50
feet square was used at each location.
The NBS narrow-band field
strength traces, with a timing trace, were recorded on a multi-beam
oscilloscope, as shown in Figure 2. Another oscilloscope and camera
recorded the broad-band pulse. The DRL stations recorded the broad-
band waveforms.
The Air Weather Service (AWS) used a crossed-loop
goniometer and recorded azimuths. In addition to other equipment, all
distant NBS and DRL stations employed one standard recording channel
with the same electrical characteristics, This channel, fed by a
cathode follower, used a standard amplifier with a flat response over
about 8 to 20 ke, and a gain of about 1,000. Reports by NBS (Reference
4) and DRL (Reference 5) should be consulted for further details.
The Air Weather Service operates a net of low-frequency (10 kc)
narrow-band (about 0.5 ke) direction-finding stations for locating
thunderstorm areas as an aid to weather forecasting. The equipment
consists essentially of two identical amplifiers each fed by identical
loops, one oriented north-south and the other east-west.
The output of
one amplifier is connected to the vertical plates and the other to the
horizontal plates of an oscilloscope. The voltages add vectorially and
the oscilloscope presentation shows a line indicating the direction of
arrival of the pulse with a 180-degree ambiguity. To remove the ambiguity, a vertical antenna receiving the electric vector and driving the
grid of the cathode ray tube through a third identical amplifier can be
used to cancel a portion of the oscilloscope presentation.
The azi-
muthal flashes on the oscilloscope face, together with 0.1l-second and
15
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