[Cruisin Marine]

I have always thought of a coil and capacitor in series as a rejector circuit, in that it would appear as low impedance at it's resonant frequency, in which case if it was tuned at 3.5 MHz it would shunt output to ground, not double it, so wondering if the coil and cap is broadly tuned for 1.9 MHz, or have I got it wrong again?

A coil and cap in series (ie from signal source to signal load) is an acceptor cct at resonant freq. (ie, it allows that resonant freq. through), If applied across a point of signal down to earth, it is again an acceptor cct and shorts that resonant freq. down to ground (ideal for notch filtering).

Conversely, a parallel tuned cct wired in the signal path is a rejector cct and will act as a "trap" (Or notch if you prefer) of energy at resonant freq.
If wired across signal line down to earth it is once again a rejector and makes sure the resonant freq. signal is kept away from being "shorted" to earth on its path, so "boosts" only that resonant freq. if you like.

It is all down to usage.