THE COLLINS 45A TRANSMITTER
The 45A was perhaps one of the most popular transmitters from the mid to late 30's. While floor standing transmitters were the norm for medium powered CW transmitters, the 45A was a sharp looking self-contained desktop transmitter running 120 watts CW, 40 watts phone. It measured 21"W x 15"D x10"H and weighed in at a mere 130 pounds. Installation involved simply connecting AC power, a key and or microphone, and the antenna.
Promoted as a powerful yet compact desktop transmitter ("a real high-powered baby" -- Nov. '35 QST), it was sold to amateurs, commercial users and police departments.
45A
Transmitter
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Courtesy of Gary - WA9MZU
In the original 1935 model, the tube lineup was a Collins C100A driving a 46 buffer, driving an RK-23 which in turn either drove an 830 multiplier, or the C201 final. A later (1937) model replaced the C100A oscillator
with a 6L6 and the final with a 211H (a 211 with a plate cap). Rapid frequency change was accomplished by swapping out two plug-in frequency change
assemblies. The first was an "interchangeable frequency shift unit", an aluminum module that housed the crystal, the oscillator tank coil, and an option multiplier coil. Banana pins mounted on
its bakelite bottom provided the electrical connections to the main chassis. The second was the final tank assembly which contained the driver coil cleverly positioned
partially inside the final tank coil to do double duty as an inductive neutralization element as a legal workaround to the capacitive neutralization workaround. A rack and pinion provided
The 45A was a collection of pioneer works publicized in trade magazines of the day. For example, it featured high performance grid modulation, the subject of an article Art Collins published in QST magazine in April of 1935.
