It's important to remember that China uses normal broadcasting to jam Sound of Hope. They seem to reserve the infamous Firedrake for Radio Free Asia, but it's CNR1 in most cases, especially Sound of Hope. So if you can copy anything at all, it's almost always going to be jamming. Ron's advice about the time pips is the clearest clue you'll get if you can't understand Mandarin, but if you don't have the time, finding a free and clear CNR1 broadcast that's not on a SOH frequency is good for comparison. Also, Sound of Hope does have a us-based .org website with streaming, so that's also available for comparison, albeit with the caveat that online streams almost always have significant time lags compared to the broadcast.
But if time's short and you can't get station ID or wait for the top of the hour, the safe assumption is CNR1. Especially if the signal's good.