A comparison of the technical aspects on the LC tank circuit circuit and a half-wave antenna.
In this thread I will refer often to these two figures
Fig. 1 is a well-known figure of all, it is a LC tank coil consisting of a coil and a capacitor.
The fig.2 is a half wave antenna consisting of 2 times ¼ wave which makes us a total length of lamda divide by 2.
When you compare the two figures you can see very quickly that there is a very big difference both physical and technical between the two, I explain myself.
The 4 main parameters to compare are: directivity, polarization, impedance and frequency.
For the coil of Fig.1 a tank coil, when the coil is cut to a certain length, there is resonance at a certain frequency and the fact of winding increases its inductance. It is helped by a capacitor to more precisely reach the desired frequency. The radiation of a coil is at its maximum in its center ie inside the coil so its directivity is at its maximum when it is located on the top of another coil and not at the inside, in order to have a maximum magnetic exchange.
As an example in the case of the Don Smith generator L1 is on the top of L2 coil and not on the inside. The polarization of a tank coil is infinite resonance and is governed by the rule of the right hand RHR and its impedance is infinite at resonance.
Regarding our fig 2 the antenna is not rolled like a coil but straight, it will resonate at the cutoff frequency and its directivity is omnidirectional and the power transmitted. Moreover the end of the quarter wave should never be connected to any other electrical component otherwise we would have an mismatched antenna , instead of having an impedance of 73 ohms, as we should have, it will be a mismatch with a stationary wave ratio very high SWR and no power radiate. For an antenna of this type one can have a vertical or horizontal polarization, the polarization is determined by the polarization of the antenna of the transmitter, one must have the same polarisation to the receiver to receive a signal.
After having examined these concepts on the LC tank and the half-wave antenna, we can conclude that they do not have many related links except that of their frequencies. One can not compare a tank coil to an antenna, the point of attachment of a half-wave antenna is crucial and that is what makes its impedance. The voltage in an LC tank is provided in both ends giving it an infinite resonance impedance. In a half-wave antenna the top part is the radiator and the bottom part is the ground plane and they could not be join.
Only an analogy on the word transmitter and receiver may be appropriate. Don Smith used rather the concept reactant coil and réactor coil it is much more precise.
To be continued, I hope I did not discourage you too much
Jack
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