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KF5JRV > TECH 24.02.17 13:17l 5 Lines 1001 Bytes #999 (0) @ WW
BID : 11035_KF5JRV
Read: GUEST
Subj: Superhet
Path: IZ3LSV<IK6ZDE<F1OYP<KQ0I<KF5JRV
Sent: 170224/1215Z 11035@KF5JRV.#NWAR.AR.USA.NA BPQK6.0.13
Although thermionic valves (tubes) enabled far greater performance to be gained in radio receivers, the performance of the devices was still very poor and receivers of the day suffered from insensitivity and poor selectivity. During the First World War a considerable amount of effort was devoted into resolving these problems. An intermediate solution was developed by a Frenchman named Lucien Levy, but in 1918, Edwin Armstrong developed a receiver where the incoming signal was converted down to a fixed intermediate frequency. Here it could be satisfactorily amplified and filtered. Unfortunately the idea did not gain much acceptance at first because the war ended, and superhet receivers were very expensive because of the numbers of valves they used. It took until the late 1920s before the number of transmitting stations rose to a level that the performance of the superhet was required and further developments meant they could be made more cheaply.
73 Scott KF5JRV
KF5JRV.#NWAR.AR.USA.NA
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