A software defined radio (SDR) is needed for digitizing the radio signal to feed into the spectrometer program.
Options:
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The SDR we prefer is the Airspy R2, $169. This operates in a 10 MHz bandwidth and is the SDR that the DSPIRA software is coded for.
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A less expensive option is the Airspy Mini, $99. It operates in a 6 MHz bandwidth. Only a minor adjustment to the software is needed if this SDR is used. For details see the Spectrometer Source Block Settings page here.
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RTL-SDR - the cheapest option, and the one that needs the most care. Three settings have to change: the source block, the sample rate, and the tuning frequency. Its 2.4 MHz band is narrow. The default
freqsetting places the hydrogen line outside the recorded band. The telescope works but detects no hydrogen. For details see the Spectrometer Source Block Settings page here. -
Lime - This can be used with 2 horns to do interferometry as well as a single horn. It will need to use the Lime source block in the GNU Radio program. For details see the Spectrometer Source Block Settings page here.
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ADALM-PLUTO uses the PlutoSDR source block, which needs additional installation steps on Linux. Change both its sample rate and tuning frequency. For details see the Spectrometer Source Block Settings page here.
For source block changes, see the Spectrometer Source Block Settings page here.
Cable Hardware: A coaxial cable is needed to connect the LNA to the SDR. Typically a 10 ft length is adequate, but any length up to 25 ft should work fine.