[Bloody Sam Roberts]

But in the case of SHGb02+14a, every observation has first been made at 1420 megahertz, before it starts drifting.

This one fact more than anything suggests an artefact or anomaly of the array.

[jennyp]

But in the case of SHGb02+14a, every observation has first been made at 1420 megahertz, before it starts drifting.

This one fact more than anything suggests an artefact or anomaly of the array.

Yep.