  Recent advances in Rydberg atom electrometry detail promising applications in
radio frequency (RF) communications. Presently, most applications use carrier
frequencies greater than 1~GHz where resonant Autler-Townes splitting provides
the highest sensitivity. This letter documents a series of experiments with
Rydberg atomic sensors to collect and process waveforms from the automated
identification system (AIS) used in maritime navigation in the Very High
Frequency (VHF) band. Detection in this band is difficult with conventional
resonant Autler-Townes based Rydberg sensing and requires a new approach. We
show the results from a new method called High Angular Momentum Matching
Excited Raman (HAMMER), which enhances low frequency detection and exhibits
superior sensitivity compared to the traditional AC Stark effect. From
measurements of electromagnetically induced transparency (EIT) in rubidium and
cesium vapor cells, we show the relationship between incident electric field
strength and observed signal-to-noise ratio and find that the sensitivity of
the HAMMER scheme in rubidium achieved an equivalent single VHF tone
sensitivity of $\mathrm{100~\mu V/m/\sqrt{Hz}}$. With these results, we
estimate the usable range of the atomic vapor cell antenna for AIS waveforms
given current technology and detection techniques.
