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KF5JRV > TECH 07.02.17 14:22l 15 Lines 2815 Bytes #999 (0) @ WW
BID : 10005_KF5JRV
Read: GUEST
Subj: Transistor Use
Path: IW8PGT<IZ3LSV<IK6ZDE<F1OYP<KQ0I<KF5JRV
Sent: 170207/1215Z 10005@KF5JRV.#NWAR.AR.USA.NA BPQK6.0.13
In the late 1940s the transistor was discovered. Initially the devices were not widely used because of their expense, and the fact that valves were being made smaller, and performed better. However by the early 1960s portable transistor broadcast radios were hitting the market place. These radios were ideal for broadcast reception on the long and medium wave bands. They were much smaller than their valve equivalents, they were portable and could be powered from batteries. Although some valve portable receivers were available, batteries for these were expensive and did not last for long. The power requirements for transistor radios were very much less, resulting in batteries lasting for much longer and being considerably cheaper.
Although transistors gained a wide level of acceptance for broadcast sets, their introduction was a little slower in the professional market. The performance of the early transistors was much lower than that of valves, and this meant that high performance sets were not so easy to design. Nevertheless as transistor performance improved and field effect transistors were introduced, semiconductor technology soon started to overtake that of valves. This was particularly true of the size and weight characteristics.
Further developments in semiconductor technology lead to the introduction of the integrated circuit. This enabled radio receiver technology to move forwards even further. The fact that integrated circuits enabled high performance circuits to be built for less cost, and significant amounts of space could be saved both gave advantages.
As a result of these developments new techniques could be introduced. One of these was the frequency synthesizer that was used to generate the local oscillator signal for the receiver. By using a synthesizer it was possible to generate a very accurate and stable local oscillator signal. Also the ability of synthesizers to be controlled by microprocessors meant that many new facilities could be introduced apart fromt he significant performance improvements offered by synthesizers.
Receiver technology is till moving forward. Digital signal processing where many of the functions performed by an analogue intermediate frequency stage can be performed digitally by converting the signal to a digital stream that is manipulated mathematically is now widespread. Indeed the new digital audio broadcasting standard being introduced can only be used when the receiver can manipulate the signal digitally.
Whilst today's radios are miracles of modern technology, filled with low power high performance integrated circuits crammed into the smallest spaces, the basic principle of the radio is usually the superhet, the same idea which was developed by Edwin Armstrong back in 1918.
73 Scott KF5JRV
KF5JRV.#NWAR.AR.USA.NA
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