It's either local RFI or perhaps due to signal overload from strong nearby system(s). You can try relocating the antenna if indoors or better yet just try reducing RF gain so to speak and see if the spurs go away or just diminish in amplitude in accordance with each increment in gain reduction. The RSP1A doesn't generally overload as easy as a run of the mill RTL SDR does, but try reducing RF gain an change antenna to another location away from other electronics, IE: switch mode power supplies, computer screens, and etc.