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FERNSEH · 2nd Mar 2018, 11:48 pm

Does this set employ a Bi-grid mixer valve? This type of valve is unlike an RF tetrode, instead one grid accepts the radio signal and the other output from the local oscillator. At 140Kc/s your set has a surprisingly high intermediate frequency for an early superheterodyne receiver. Some 1920s superhets had an IF of 50Kc/s.
An example of a Bi-grid valve: http://www.r-type.org/exhib/aaj0031.htm

Also: http://www.r-type.org/articles/art-094.htm

DFWB.

2nd Mar 2018, 11:48 pm	#2
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Supersonic Heterodyne radio 1920's. Does this set employ a Bi-grid mixer valve? This type of valve is unlike an RF tetrode, instead one grid accepts the radio signal and the other output from the local oscillator. At 140Kc/s your set has a surprisingly high intermediate frequency for an early superheterodyne receiver. Some 1920s superhets had an IF of 50Kc/s. An example of a Bi-grid valve: http://www.r-type.org/exhib/aaj0031.htm Also: http://www.r-type.org/articles/art-094.htm DFWB.