Are the answers all capital cities of countries, or are some State capitals?
I can't think of the answer but the only 4-letter country capitals I can think of are:
Lome, Rome, Lima, Male, Doha, Baku, Riga, Oslo, Kiev, Suva, Apia, ....... & possibly (Port) Vila, Gaza (City).
I imagine you've already used some of these, so by a process of elimination you - or someone else - may be able to work it out.
Its Riga. Listeners living in Latvia and its surrounding area can once again tune to Radio Caroline on 945 kHz medium wave twice a week. Two of our programmes, the popular 60's & 70's Request Show and Rob Leighton's Imagination programme, are being relayed via the transmission facilities of Radio Nord which broadcasts to Latvia's capital city Riga with a claimed audience of 100,000.
UK-based satellite/Internet station Radio Caroline announces on its website that �from Thursday, 7th September listeners living in Latvia and its surrounding area will once again be able to tune to Caroline