Sources with precession modulation: total number: assuming all binaries have significant spin–orbit misalignment, the number of sources with precession periods P _min = 1 minute and P _max = 1 year (blue) or 1 month (green) over the entire sky, with flux above F/ . To guide the eye to scales comparable to future radio surveys like VAST (T. Murphy et al. 2011, in preparation), a horizontal dashed line corresponds to 1/10 ⁴ deg ² and a vertical dashed line corresponds to 1 mJy.