  We report on the construction and testing of a vacuum-gap Fabry-P\'erot
etalon calibrator for high precision radial velocity spectrographs. Our etalon
is traced against a rubidium frequency standard to provide a cost effective,
yet ultra-precise wavelength reference. We describe here a turn-key system
working at 500 nm to 900 nm, ready to be installed at any current and next
generation radial velocity spectrograph that requires calibration over a wide
spectral bandpass. Where appropriate, we have used off-the-shelf, commercial
components with demonstrated long-term performance to accelerate the
development timescale of this instrument. Our system combines for the first
time the advantages of passively stabilized etalons for optical and
near-infrared wavelengths with the laser-locking technique demonstrated for
single-mode fiber etalons. We realize uncertainties in the position of one
etalon line at the 10 cm/s level in individual measurements taken at 4 Hz. When
binning the data over 10 s, we are able to trace the etalon line with a
precision of better than 3 cm/s . We present data obtained during a week of
continuous operation where we detect (and correct for) the predicted, but
previously unobserved shrinking of the etalon Zerodur spacer corresponding to a
shift of 13 cm/s per day.
