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Test # 106


1.
How many times do the hands of a clock coincide in a day?

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Idiom of the Day

bring up (a child)
to raise or care for a child
My sister is bringing up three children.
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  • Guglielmo Marconi

    Marconi rebuilds the transatlantic stations

    The collapse of the antennas at Poldhu and Cape Cod dealt a devastating blow to Marconi. He had invested enormous sums into the building of these two stations and their antennas.But Marconi did not let this setback defeat him. With typical resilience he set about the task of rebuilding. This time he made the Poldhu antenna smaller and more robust.He also decided to move the site of the American station to Newfoundland to shorten the distance of the path. At this location he decided the antenna would have to be kept as simple as possible consisting of a wire supported by kites or balloons this was no doubt in some degree due to the cost of rebuilding a full antenna system. This also meant that a transmission could only be made in one direction from England to Newfoundland.Tests commenced in December 1901 with the Poldu station transmitting the letter s consisting of three dots, for three hours every day. This letter was chosen for two reasons. The first was that it would be easy to recognise. The second was probably more important. The transmitter was a very new design and it could not be trusted to transmit dashes without the risk of a breakdown.

    The weather in Newfoundland was bad for these tests. On the first two days kites were lost because of the strength of the wind. A third kite was tried, but this moved rapidly in the wind causing the resonance of the antenna to change rapidly, and it was not possible to counteract this with the receiver tuning sufficiently fast.In order to be able to detect the signals under these difficult conditions Marconi reverted to an untuned circuit and what was called a selfrestoring coherer. Despite its name this was not a coherer at all, but an early example of a detector that operated by rectifying the signal in the same basic manner as diode detectors do in amplitude modulation, AM receivers. This was used with a sensitive telephone earpiece to enable Marconi to listen to the signals.Despite these difficulties, Marconi was convinced that he could hear the signals. He asked his assistant Kemp to confirm this which he did. Marconis notebook indicates that he heard signals at 12.30 pm, 1.10 and at 2.20 on 12 December 1901.The weather worsened and with no sign of a letup in the conditions an elated Marconi released the information to the press despite the fact that he had no independent witness, nor any instrumental record. This news was received enthusiastically by the press, although the scientific community was more sceptical. They thought he might have mistaken static cracks for the Poldhu transmissions.


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