A horn on a stand is an antenna, not yet a telescope. What makes it one is the receiver chain: a low-noise amplifier on the probe inside the can, which lifts a signal far too faint to digitise up to something an SDR can see, and a software-defined radio that samples the amplified signal and hands it to a computer over USB.

The amplifier is the component that decides how good your telescope is, and it is the one most worth spending time on. There are three routes to one: build the DSPIRA board from parts for around $30, or buy one of two ready-made modules.

The SDR matters less. Several will work, but each has its own sample rate and gain, and the spectrometer has to be told which one you have. That is what the source-block settings lesson is for.

Read this module alongside Software Setup, which covers the programs the SDR feeds.