Leonard Stanisław Danilewicz was a Polish engineer and, for some ten years before the outbreak of World War II, one of the four directors of the AVA Radio Company in Warsaw, Poland.
The company took its name from the combined radio callsigns of the Danilewicz brothers (TPAV) and Palluth (TPVA).
When the company was being formed about 1929, the Danilewicz brothers were short-wave "hams" and students at the Warsaw Polytechnic.
[3] Leonard Danilewicz early showed remarkable creativity as a radio designer, coming up with a concept for a frequency-hopping spread spectrum: In 1929 we proposed to the General Staff a device of my design for secret radio telegraphy which fortunately did not win acceptance, as it was a truly barbaric idea consisting in constant changes of transmitter frequency.
The commission did, however, see fit to grant me 5,000 złotych for executing a model and as encouragement to further work.