What does the output of a radio telescope look like?

[accdd]

What does the output of a radio telescope look like?
I suppose it is not an image like that of a telescope observing visible light

 

[Hyperfine]

Typically a plot of signal amplitude as a function of frequency. So a baseline with a peak, very similar to what a spectrum in any frequency domain looks like.

Often the images of a radio emitting region will be illustrated via contour lines depicting the signal magnitude. As an example from NRAO: Viewing a contour plot.

 

[Baluncore]

What does the output of a radio telescope look like?

The observation is recorded over a period of time.
The bandwidth of the signal is determined by the antenna and receiver selectivity.
The signal voltage is digitized, so it can be analyzed later using signal processing.
In effect, the antenna and receiver is a thermometer and the signal represents a temperature.
The signal sounds like frying white noise.
With an antenna aperture over about 500 m², the brightest pulsar can be heard in real time in the noise.

Accurate radio images are synthesized by recording the same area of sky, with many widely spaced antennas and receivers, simultaneously as the Earth rotates. The recorded signals are later synchronized, then correlated to produce the image.
https://en.wikipedia.org/wiki/Very-long-baseline_interferometry