The Isobel is located at "longitude 60, latitude 30", which, as well as being hopelessly vague, could put it at 4 points on the globe. The most likely however is to the east of Bermuda.
The earliest documented telecasts of this film took place in Cleveland Thursday 3 June 1948 on WEWS (Channel 5) and in New York City Thursday 11 November 1948 on WATV (Channel 13).
In the early airshow scenes Wilma Howell is flying an autogyro, sort of a cross between a helicopter and an airplane. Unlike a helicopter an autogyro can not take off vertically. It's the forward momentum of the autogyro that causes the overhead blades to spin and provide lift. The autogyro in this film is likely a Pitcairn PCA-2 which were developed in the United State in the early 1930's. Autogyros, with obviously more modern designs, are still manufactured.