One reason the units remained separate, other than weight and size constraints, is that purchasers often wanted to add only a transmitter to an already existing medium wave AM receiver installation in an automobile (California Highway Patrol, for example.) It should also be noted that within months of completion of the Link system for Connecticut, Noble had joined Motorola, Inc. O." equipment designation was, other than that it was the first equipment actually manufactured by GE, at their Bridgeport facility, beginning in 1941.and Motorola was producing a two piece VHF FM radio of their own called the "Deluxe" line, which not surprisingly, appeared very similar to the Link 1940 FM equipment. using designs created by GE engineers in Schenectady, N. That equipment is believed to be the E-1 Series shown below.General Electric was an already well established manufacturer of a broad spectrum of electrical and electronic material when it decided to enter the land mobile (police) radio market in 1931.GE's initial land mobile radio products were mobile and motorcycle receivers for the AM medium frequency police channels in the 17 KHz bands, and in the early 1930's the company branched out with an experimental VHF AM two way set, using a super-regenerative receiver, but which was more or less a toy rather than a serious police tool.
Note the huge dynamotor which GE referred to as an advantage because it offered "continuous duty transmitter operation." It should be noted that equipment like this placed a huge drain on 6 Volt car batteries and electrical systems, often requiring changing of batteries at the end of each shift!
GE had applied to the FCC for an experimental license for FM operation on 49 MHz which was granted on August 3, 1938. FM (at 15 k Hz /- deviation) on September 28-29, 1939, with Maj.
Edwin Armstrong in attendance, for the FCC Emergency Service administration.
AM production by all major manufacturers stopped by 1950, other than by special Noble's experiments, on a somewhat experimental basis, in coordination with Maj. Armstrong is usually referred to as the "inventor" of FM although at least one patent was taken out prior to 1910 describing FM transmission.
Armstrong's patents, perhaps more correctly described, covered the first actual practical application of FM.