[Antennas] Link vs Pi

[Adam Farson]

Hi Steve,

As I recall, the pi-network is a little more efficient, as there is less
coupling loss between the input and output than with the link-coupled tank
circuit (which is a loosely-coupled air-cored transformer.)

The pi-network was originally adopted for several reasons. It provides a
better match to a coax feedline if properly designed, and also acts as a
low-pass filter to suppress harmonics generated in the PA. An outboard
low-pass filter is usually required between the output of a link-coupled
tank circuit and the antenna, to ensure regulatory compliance regarding
spurious and harmonic suppression. The insertion loss of the extra filter
at the fundamental may be 1 dB or more.

Cheers for now, 73,
Adam VA7OJ/AB4OJ



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