Bipolar Regenerative receiver
Contrary to what some radio experimenters think, a bipolar regenerative design can be made to work efficiently. The major concern is the low input impedance of the detector-amplifier bipolar stage. Nevertheless, it can be easily compensated with positive feedback or regeneration. A sufficient amount of regeneration can make tuning astonishingly sharp. Another concern is the quality of the detected audio. This, to my knowledge, is subjective. The quality of sound coming out from an earphone can be rated good or fair by two different people. I would suggest that you decide by yourself. So, come on and try the following schematic for the 530 kHz to 1650 kHz AM Broadcasting Band.
Bipolar Regenerative receiver circuit
Please notice that the 475 pF variable capacitor tunes in the stations
whereas the 200 pF variable capacitor controls regeneration. The latter is known
as the throttle capacitor. L2 is the tickler coil. In order to regeneration to
take place, L1 and L2 must be correctly phased ( very important! ).
The power consumption is very low. The 2N3904 drains some 60 uA from the 9 volt
battery and the AC126, about 0.5 mA.As a benchmark, medium powered ( 5 to 10 kw
) local stations within 25 km from my site are heard as fair to loud audio
signals.
The audio output stage has no external bias, and doesn't need any. This is
because Iceo, the leakage collector current ( about 0.5 mA in my prototype ), is
sufficient to build up a usable Beta ( or current amplifying factor ) in the
germanium AC126 transistor. This is a bit unusual but it works fine. Also, the
signal detection is carried out by the 2N3904 transistor, as it is driven,
thanks to regeneration, into its non-linear region. In other words, it works as
an amplifier-detector.
Bipolar Regenerative receiver Prototype
Author: Ramon Vargas-Patron
Title: Bipolar Regenerative receiver
electronic circuit
Source: unknown
Published on: 2006-01-15
Reads: 1861
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