Valve Radio and Audio Repair Handbook

Chapter 11

What you need to know about the superhet

Chas E. Miller

In a previous chapter we discussed how the selectivity and sensitivity of a receiver may be improved by adding more tuned RF amplifier stages. In theory half a dozen or more stages might be added until the required performance was achieved, but in practice the need for six sets of tuning coils, six lots of wavechange switches and six tuning condensers, plus the necessity to keep them in perfect alignment over perhaps three or more wavebands by means of a vast number of trimming condensers, would make the exercise impossibly complicated. The superhet receiver makes it possible to have eight or more tuned circuits with no more RF tuning components than in a three-valve TRF. It does ...