Right, the first picture was something I actually noticed on a friend's machine. Honestly, I don't know why his is acting up at that lower frequency. He could have been using cheap coax, but I'm not certain. On my setup, it behaved much better. Your setup even looks better than mine. Maybe a better coax or the use of sma attenuators?
markone - the noise floor can get as low as -135 db, but to get there, like with any spectrum analyzer, you have to limit the input bandwidth. To get to -135db, I have to 1) turn on the pre-amp 2) reduce the bandwidth to about 100 or so hertz, and possibly reduce input attenuation. I did not do this for my demonstration as it would have taken too long to sweep the entire 1.5 Ghz and was not necessary. Again, I think it's a good buy. It won't perform the same as a $10k+ unit, but then again, unless you want to spend 10k+, your options are limited.