You 'may' be able to improve your antenna's performance by the following.
'System noise figure' is pretty much determined by the first stage in the system.
That first stage would be your coax and the loss will add directly to your noise figure.
So essentially, if you had a perfect receiver with a 0 dB noise figure, fed by coax with 9 dB of loss, your overall system noise figure would be greater than 9 dB. NOT very good.
Refer to this calculator. Cascaded Noise Figure Calculator
And this old post of mine.
Splitter, Amplifier, & coupler Noise figure
Assume that the first 'stage' in your system is your coax and enter it into the calculator as a negative number.
One problem many people have is using a low quality amplifier with too much gain.
That will increase the probability of overload and other problems.
It you add a low noise preamp right at the base of the antenna that is equal to the loss of your feedline (plus about 3 dB) you 'should' see a dramatic improvement.
That is assuming that you have no very strong signals nearby.
I run eight antennas. Five ST2 antennas, and three commercial antennas. All but one of them has a preamp right at the base of the antenna and they're all perfectly stable.
I have one antenna without a preamp for two reasons.
1. If I want to listen to MilAir, those with preamps have too many SatCom signals in the 200-300 MHz range.
2. I need something to use during power outages that requires no power supply.
If you listen to my feed, you'll see how an ST2 with a good preamp works.
It's feeding 32 scanners at the same time.