Tobin Fricke wrote:
On Tue, 24 Jan 2006, wrote:
The trick with regens is to couple as loosely as possible. There is
enough gain in most regens that even a very loose coupling is enough
to overlaod and flatten out the selectivity.
Could you recommend a good introduction to the theory of the
regenerative receiver (and superregen)?
thanks,
Tobin
I'll recommend a little book that is readily available. "Secrets of
Homebuilt Regenerative Receivers" by C.F. "Rock" Rockey. Its a Lindsay
Publications book.
Rockey does a good job at simplifying the simple
Basically the
concept of a regen is feeding the output back into the input for
reamplification. Theoretically its a somewhat infinite process in that
the reamplification continues repeating itself resulting in very high
gain at the particular frequency the set is tuned to and thats also
where the selectivity improvement comes from.
Its similar to oscillation in a tube.
The coupling issue mentioned by Allison is related in the sense that
heavy antenna loading will decrease the circuit Q and consequently
decrease its selectivity as the regenerative signal makes its round-trip
thru the circuit. That opens the window for strong stations that are
well off frequency to easily overload the circuit as a whole due to the
high magnitude of amplification. You'll see some circuits with direct
antenna connections to the tank circuit (bad)...some use a separate
antenna winding on the coil (better) some use capacitive coupling to
the tank...some use a combination of both.
Easy enough to build one for grins...might not be as stable as you would
want for your decoding project but would be a good, fun exercise just
the same.
GL,
Bill