Both campana and campaña refers to either bell or campaign.
Both the spelling seems to be correct.
Campo is a field; campamento is a camp.
The title of a blog is: TIENDAS DE CAMPAÑA PARA IR A CAMPINGS
What does the word "campaña" mean here?
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Tienda de campaña is a construct to define a tent.
Here "campaña" has the meaning of campaign, as traditionally military armies used those tents as shelter were traveling for long journeys on a campaign.
With the pass of the years, tents got an amusement use and evolved to more comfortable and friendly designs from their military ancestors, but their original name remained the same.
Campaña has several meanings, including field extension. A tienda de campaña is the compound word to define the portable shelter intended to be placed in the field to protect one or more people.