translated: are they radios there? rejected. My interpretation was "are they radios or something else that I see there?
I don't think it's an accurate translation of this sentence. The vannak here definitely means "are there," as in, "do there exist."
Remember, van and vannak are omitted in predicate-nominative type sentences where you're saying "X is Y" or, in questions, "Is X Y?" If you wanted to ask, "Are they [those things there] radios?" you would go with something like, Azok ott rádiók?
The stress accent is on the first syllable where you'd expect it. What you're hearing is the pitch rise on the second-to-last syllable of the sentence to indicate the question (and then it falls again on the last syllable).
No, I don't think that's accurate.
Vannak rádiók? = "Are there radios?" as in, "Do radios exist?" Vannak ott rádiók = "Are there radios there?" as in, "Are there radios not just in general, but at that specific place?"
Simply, "Are there radios?" does not express the location involved in the question.