The Gain or Q of a parallel tank circuit with high impedance load, R, is as follows;
Q=R√(C/L)
So make L small but long as you can to pickup µV/m signals such as 1m vs 10cm.
But keep L small and use larger C , so that stray capacitance does not detune antenna.
Use Plastic film cap with 100M resistance and front end FET with similar high impedance. Lower Coil impedance will shunt ESD and lighting noise while raising Q.
At resonance antenna impedance=R only but off frequency drops quickly to provide filter gain.
Other methods use impedance gain by series to parallel auto transformer for N factor improvement.
high inductance // tank circuits are used for gain when driven only by current sources or H field coupling, so it depends what on if you are detecting near H fields or far E fields.
for near H fields a large loop is better.
for far E fields a long coil is better.
Open field LF antenna detects E field high is voltage at free space impedance.
Try to choose cap well below 1000 pF for selecting L so that series R of inductor is negligible or high Q inductor ZL/Rs
thats my 2 cents
more..
e.g. 470pF//2.1mH @160kHz =~2.1kOhm so 1MOhm R load might achieve Q=500 if coil Q is higher meaning <2 Ohm Rs.
higher L and smaller C is possible if winding capacitance is lower, but keep in mind antenna is like a transmission impedance transformer between free space and high Z input preamp, so ideal impedance is stepup tuned transformer , otherwise ZL(f)= RMS Z(f) or root of {free space source Z^2 and high R load^2}