This Collins 51J-1, serial number 9, was donated by engineer Bill Lund in 2004. Originally used by CBS to pick up Edward R. Murrow's, and other CBS war correspondents' broadcasts from Europe during WWII. It was part of a "triple diversity" arrangement with two other 51Js tuned to the same frequency. The radios each had an external AVC bus connection on the back that allowed the receiver with the strongest signal to mute the gain of the others. That way, the set with the best reception at any given moment was the one that was heard. Each receiver had a separate antenna, located miles apart and each having different polarization.
The Collins 51J-1 was the first version of an outstanding line of general coverage receivers.
It tunes continuously from 500 kHz to 30.5 mHz in 30 different bands.
The remarkable Collins Permeability Tuned Oscillator (PTO) had a precisely wound coil and a mechanical corrector mechanism to modify the slug movement to produce a linearity better than 1 kHz in 10 turns.
The four-page brochure describing the 70E-8 PTO (shown at right) is dated 1947.
The PTO in our 51J-1 (below)is marked 70 E-7A.
Our copy of The First Fifty Years: A History of Collins Radio Company and the Collins Division of Rockwell International lists the production dates for the 51J-1 as 1945 - 1948.
We wrote to Collins in Cedar Rapids, Iowa. Our contact there has never seen one. Near as he could tell, they only made about 150 of the original 51J-1s before production was switched to the upgraded 51J-2 in 1949.
The image (below) showing the Collins product line (including the 51J-1) is from the 1946 ARRL Handbook which was printed in November of 1945.