BC-728, developed 1943,

is a warning or alarm receiver, to be carried or mounted on a vehicle. The BC-728 was used at artillery locations. There would be a "forward observer" radioing back information on which direction to change the aim.

Frequency range 2.0 to 6.0 MHz in 4 preset channels switched by pushbuttons.
Power supply 2-V Battery TM 11-859, Consumption 1,85 A.
Modulation AM
Receives only tone and voice.
Antenna 7 foot telescope; if carried, carried on the looped antenna cable.
Weight: 10.2 kg. ( Today it would NOT be called "portable".)