ARLA/CLUSTER: A história do Radio Super-heteródino

[João Costa > CT1FBF]

Em electrónica, um receptor super-heteródino (muitas vezes abreviado a
superhet), inventado pelo engenheiro norte-americano Edwin Howard Armstrong
em 1918 durante a 1ª Guerra Mundial, usa mistura de frequências ou
heteródino para converter um sinal recebido numa frequência fixa intermédia
(IF), que pode ser mais convenientemente processada do que a frequência
rádio portadora original. O receptor super-heteródino foi criado com o
objetivo de reduzir os problemas do receptor AM-DSB padrão, no caso o
receptor de Rádio-Frequência Sintonizada. Praticamente todos os receptores
rádio modernos usam o princípio de super-heteródino.

O problema maior do tipo radiofrequência sintonizada era o fato da
seletividade variar ao longo da faixa.
*****************************************************************Superhet
Radio History*

*Electronics Notes* tells the story of how the superhet radio was born.
Today we all take the superhet radio for granted. It has always been there
and given good performance. But how often do we step back and think about
when and how it was developed.

The idea for the superhet radio, superheterodyne receiver or to give it its
full name the supersonic heterodyne receiver was developed back in the days
of the First World War.

The need for it arose from the military needing receivers that had more
gain and more selectivity. At the time, valve (or tube) amplifiers
operating at high frequencies of anything above 100 kilocycles per second
(kHz in modern parlance) or more tended to burst into oscillation. Even
then they often had little gain.

This was a problem that taxed the minds of many people, but by the end of
the war, the first superheterodyne radio had been built. It provided a
significant improvement in performance over anything else that was around
at the time, and in many was it was revolutionary.

However, after the war, it fell into disuse. Valves of the time were very
expensive, and they also needed separate batteries to supply them as the
indirectly heated valve had not been invented. This made them prohibitively
expensive for all but the most affluent of organisations.

After the indirectly heated valve had been invented, allowing valves to be
mains powered, and with the growing number of stations on the air, the
superhet started to come into mainline use for broadcast reception as well
as for many other communications applications. Once established it became
the main format for radio receivers.

Read the whole story on Electronics Notes :
https://www.electronics-notes.com/articles/history/radio-receivers/superheterodyne-radio-receiver.php

73  *Ian G3YWX*
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