sga-4586
You can use this but if you are looking only for a narrow band (i.e. GPS) you can probably do better than NF=1.8 dB. You also have to consider P1dB or IP3. If your input signals may be strong, or have a strong jammer next to a weak signal, your LNA must be capable of amplifying without much distortion or intermod products, or else you'll need a pre-slection filter before the LNA which degrades your noise figure. You need to do a budget analysis of your down-conversion chain to find out how much dynamic range is needed out of each stage.