The Influence Of The Antenna On Regeneration
The Influence Of The Antenna On Regeneration
When looking at regenerative receivers using inductive feedback and also employing an antenna coil to inductively couple the antenna to the input tank it becomes clear that between the three coils (antenna coil, tickler coil and input tank coil) there's not only the only the desired coupling between the tickler coil and the input tank coil, respectively between the antenna coil and the input tank coil but also some degree of coupling between the tickler coil and the antenna coil.
Of course, along with the input voltage showing up in the input tank some of the antenna's capacitance and loss resistance is reflected into the input tank introducing detuning and higher losses into the input tank. The latter requiring a larger amount of positive feedback (regeneration) for compensation. This has been extensively covered in the literature.
However, beyond this the question that naturally arises is: Does the coupling between the tickler coil and the antenna coil alter the feedback (regeneration) behavior of the circuit itself? This question is investigated in the paper presented here. For further reference, the abstract section of the article is quoted below.
The regenerative receiver using inductive feedback has been one of the most common TRF (Tuned Radio Frequency) AM radio receiver designs. In these receivers, the antenna is often coupled inductively to the input tank using an antenna coil in the receiver with antenna and ground connected to the terminals of this coil. In most cases the feedback (tickler) coil providing feedback into the input tank is not only coupled inductively to the input tank, there also is some inevitable inductive coupling
to the antenna coil. In this article, we shall therefore take a closer look at how feedback (regeneration) is altered by the presence of the antenna. It is shown that if the antenna circuit is below it’s resonant frequency the amount of regeneration provided to the input tank is increased, while if the antenna circuit is above it’s resonant frequency the amount of regeneration decreased. However, for reasonable circuit parameters these changes in regeneration are relatively small and in general of no concern. If, however, the resonant frequency of the antenna circuit is within the reception frequency range the regeneration behavior of the receiver will, although perfectly deterministic, appear as erratic to the user near the resonant frequency of the antenna circuit.
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