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KF5JRV > TECH 13.02.17 14:24l 29 Lines 1800 Bytes #999 (0) @ WW
BID : 10355_KF5JRV
Read: GUEST
Subj: Triode Uses
Path: IW8PGT<IR2UBX<IW2OHX<UA6ADV<CX2SA<N0KFQ<KF5JRV
Sent: 170213/1215Z @:KF5JRV.#NWAR.AR.USA.NA #:10355 BPQK6.0.13
Despite the success of the cat's whisker, work did not stop on the development
of thermionic technology. An American named Lee de Forest was a competitor to
Marconi and needed to develop receiver technology that did not infringe any
patents to which Marconi had access. To achieve this he devoted a large amount
of time in developing a thermionic detector which did not infringe Fleming's
patents. He took out a number of patents in the period between 1905 and 1907
covering a variety of developments that culminated in the form of the triode
valve in which there was a third electrode called a grid. He called this tube
an Audion. With the benefit of hindsight it seems amazing that the Audion was
initially used as a leaky grid detector and it took until 1911 for it to be
used as an amplifier. Once this fact had been discovered many people were quick
to exploit this fact in a variety of applications. One of the first areas in
which valves were used was in the manufacture of telephone repeaters, and
although the performance was poor, they gave significant improvement in long
distance telephone circuits.
With the discovery that triode valves could amplify signals it was soon noticed
that they would also oscillate. This was a mixed blessing. It was a great
disadvantage because these early valves were very difficult to stabilise when
used for signals above a few kilohertz. However the fact that valves could be
used as oscillators was exploited in generating signals. Previously high
frequency signals had been difficult to generate. If steady signals were
required, electromechanical techniques had to be used, and these had obvious
frequency limitations. With the use of valves it was possible to make
relatively compact electronic oscillators.
73 Scott KF5JRV
KF5JRV.#NWAR.AR.USA.NA
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