Having lost both parents at a relatively early age, he supported himself and his sister, Janina, by fixing and installing radios for the Polish military.

In 1940 he started working for the Galvin Manufacturing Corporation in Chicago (the company changed the name in 1947 to Motorola) and assigned to a team that developed the SCR-300, the first radio used by American forces in Europe to be called a "Walkie-Talkie".

[5] As principal RF engineer on the project and named on three patents for the device, Magnuski is sometimes credited as having "invented the Walkie-Talkie in America".

[6][4][1] He later received a U. S. Navy Certificate of Commendation for Outstanding Service for development of the AN/CPN-6 Radar Beacon, a microwave device which aided carrier pilots to find their ship during low visibility conditions.

He helped in the development of VHF cavity resonators that allowed adjacent channel operation, was a key designer for the Motorola Sensicon receiver which used a selective filter in front of the IF amplifier and created microwave relay equipment for use in transmitting multi-channel telephone, data and TV.