What is it?
The circuit in fig. 1 (.bmp) can best be described as an RF converter followed by a tunable regenerative detector. There are many advantages to this scheme:
Selectivity:
The detector is allowed to operate on a low frequency, where these type operate most efficiently. With the resultant higher Q tuned circuits there is greater inherent selectivity.
Stability:
The detector is isolated from the antenna, greatly reducing signal generation, keeping varying antenna reactance from affecting the tuning and loading of the detector. The detector is allowed to operate under a more constant load environment.
Tuning:
The tuning rate is constant for all bands because the detector tuning range never changes. Band changing is just a matter of switching a crystal, not a coil. This allows for instant band changing.
Sensitivity:
The front-end provides some conversion gain ( as well as increased selectivity) thereby presenting the detector with an amplified signal.
Construction:
This receiver is no more difficult to build than any two or three tube regenerative receiver. Coils are few, easy to make, and permanent. I built three of these radios so far, and each one averaged two afternoons of construction time.
