Sentencing Stephen Gough, judge Sarah Munro QC said: "This is a much more serious offence than the other public order offences. In those circumstances I take the view only a substantial custodial sentence is appropriate."
She said that Gough, who has been on remand, will be eligible for release on August 14 - one day after there is a hearing at Southampton Magistrates' Court to impose a full Asbo on the former Royal Marine.
The judge conceded that, if she had allowed Gough to leave by imposing a sentence commensurate with his time already served: "There is a reality here that he will walk out on these steps naked. I do not think I can ignore that reality.
More top news
Royal Navy vessels are following Russian warships 'every inch of the way' as they pass through the English Channel on their way to Syria.
Friday's forecast for the east of the region
Friday's forecast for the west of the region