09-08-2013, 12:25 AM
It would have been no earlier than 1924, since that was when the first commercially-manufactured superhet wireless sets were becoming available, these being single-conversion, of course. My research (Radio! Radio! Jonathan Hill; ISBN 0 9511448 71) states that the first one was the 7-valve 'Western Electric' Model 44022.
Following that, wireless 'amateurs' would have been building add-on convertors for their superhet wireless sets. In 'Radio Engineering' by F.E. Terman, published 1932, page 484, there is a reference to, and a circuit diagram of, a short-wave adapter for a broadcast receiver: this is an external 'add-on' tuner. Although not a self-contained superhet, this approach probably represents the earliest period of the principle of the double superhet being used.
However, it also seems likely that the double s/het, as a self-contained wireless, in the early stages of its development would have been almost exclusively found in military applications, mainly on the grounds of manufacturing cost.
Al. / Aug. 9, 2013 //
Following that, wireless 'amateurs' would have been building add-on convertors for their superhet wireless sets. In 'Radio Engineering' by F.E. Terman, published 1932, page 484, there is a reference to, and a circuit diagram of, a short-wave adapter for a broadcast receiver: this is an external 'add-on' tuner. Although not a self-contained superhet, this approach probably represents the earliest period of the principle of the double superhet being used.
However, it also seems likely that the double s/het, as a self-contained wireless, in the early stages of its development would have been almost exclusively found in military applications, mainly on the grounds of manufacturing cost.
Al. / Aug. 9, 2013 //
