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The Engineering Development Array (EDA) is a single test station for SquareKilometre Array (SKA) precursor technology. We have used the EDA to detectlow-frequency radio recombination lines (RRLs) from the Galactic Centre region.Low-frequency RRLs are an area of interest for future low-frequency SKA work asthese lines provide important information on the physical properties of thecold neutral medium. In this project we investigate the EDA, its bandpass andthe radio frequency interference environment for low-frequency spectroscopy. Wepresent line spectra from 30 to 325 MHz for the Galactic Centre region. Thedecrease in sensitivity for the EDA at the low end of the receiver preventscarbon and hydrogen RRLs to be detected below 40 and 60 MHz respectively. RFIstrongly affects frequencies in the range 276-292, 234-270, 131-138, 95-102 andbelow 33 MHz. Cn$\alpha$ RRLs were detected in absorption for quantum levels n= 378 to 550 (39-121 MHz) and in emission for n = 272 to 306 (228-325 MHz).Cn$\beta$ lines were detected in absorption for n = 387 to 696 (39-225 MHz).Hn$\alpha$ RRLs were detected in emission for n = 272 to 480 (59-325 MHz).Hn$\beta$ lines were detected for n = 387 to 453 (141-225 MHz). The stackedHn$\alpha$ detection at 63 MHz is the lowest frequency detection made forhydrogen RRLs and shows that a cold (partially) ionized medium exists along theline of sight to the Galactic Centre region. The size and velocity of this coldH$^{+}$ gas indicates that it is likely associated with the nearbyRiegel-Crutcher cloud.

Spectroscopy with the Engineering Development Array: cold H$^{+}$ at 63 MHz towards the Galactic Centre