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Keep in mind that you only need a pre amp if the "antenna noise" is below the receiver noise.
Most receivers have reduced sensitivity at LF / MF, but the noiselevels at these frequencies is high compared to HF.
Easy to check: Listen (with connected antenna) on a quiet frequency (only noise, no signal). Next disconnect the antenna. If the noise level decreases you do not need a pre amp (in fact a pre amp will only deteriorate the IMD behavior and thus create more
ghost signals).
73, Rik ON7YD - OR7T
After, definitely
Before is applicable to VHF and up where equipment noise figure dominates sensitivity and a filter in the antenna side wold add loss and degrade overall NF
At HF and certainly LF, atmos noise dominates to noise figure is unimportant. That way you get the benefit of rejecting strong OOB signals that may stress even the preamplifier
'jnt
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