An easy test that will determine if a preamp can help you, is to tune your receiver to a frequency where there is no station, only noise. Then disconnect the antenna.  If there is a big reduction in the noise, a preamp cannot help you on that frequency.  The noise you hear is being picked up by the antenna.  If there is little or no reduction in noise, a preamp will help.  The noise you hear is being genegated in the receiver.  What you would like is that there be a big reduction in noise when you disconnect the antenna, on all frequencies.  In that case the receiver is not limiting the sensitivity.  You need to do this on several frequencies and at different times of the day.  Atmospheric and man made noise changes from time to time and day to day, and reduces as you go higher in frequency.  A preamp is most likely to help on higher frequencies.  As an example, my Kenwood R-5000 passes the test on 10MHz, but fails the test on 15MHz and above.  In other words at 10MHz a preamp will not help but at 15MHz and above it will.  Since I know that my R-5000 can be improved on some frequencies, why not use the preamp and be sure I always have optimum sensitivity on all frequencies.

I've been asked about third-order intercept.  Any intermod is likely to be generated in the receiver because of the extra gain provided by the preamp.  The best way to use any high gain pre-amp like our BBP-1020, is to leave it OFF unless it's needed for a weak station.  Then unless a spurious signal would happen to fall right on the frequency you want to hear, it doesn't matter if there is intermodulation signals on other frequencies.  It is very unlikely that any station will be readable with the pre-amp ON, and there be no evidence of it without the pre-amp, unless it's the result of intermodulation.  So when you're tuning around, leave the pre-amp OFF.  You'll find the weak ones, and have the extra gain when you need it, even if it causes spurious signals on other frequencies.