There is no such contest, but there have been a great number of radio stations that used small pennants as tchotchkes. A pennant is just a tapered flag, usually triangular but not always. These were most commonly used by shortwave stations but not exclusively.
Inside the United States shortwave is a wash. It's almost all religious talk and hams. In some other nations its more dominant than FM. These shortwave broadcasters accept correspondence from listeners, especially reports on how well the station is being received and comments on their programming. These broadcaster often respond to such letters by sending out colorful souvenir cards, known as QSL cards, [which I've talked about before] for correct reports of reception. Some station reply with QSL letters instead of cards, and a few send other items, like pennants with the station’s name or call letters, to lucky short wave listeners Today, collectors buy, sell and trade them.
Predictably I've seen them most often with international stations, but I did see one for an Alaskan broadcaster KNLS . I've never seen one from inside the contiguous 48 states. Alaska might as well be its own country anyway.http://www.knls.org/
Pennants probably came from the Naval pennant tradition. it's the sign of a warship, to be flown from its masthead while the ship is in commission. The British royal navy also started numbering them to identify ships. That tradition itself originates in a medieval military use wherein knights carried pennons. that dates to at least the 13th century.
There is also a type of antenna called a pennant. It's radio-related but off-topic today. More here