This is a Collins 651S-1 double conversion, superheterodyne, solid state, general coverage communications receiver. Collins Radio made this receiver between 1971 and 1973. This one is a 152 series receiver, which is the last in a series of 3 models. The 152 series is the latest version of the 651S-1 receivers, although this is an early receiver of the late version of the series because it still has the nixie digital readout. The last ones made had the LED readout. The MCN #15XX. The serial number is #15XX. This receiver was sold to the military and government agencies, and most of the ones I have seen had signs of extensive use. This one looks almost new, and obviously has low hours. There appears to be 3 Collins mechanical filters installed in the receiver in addition to the standard upper and lower sideband filters. I am not sure what they are. I can't see them as they are mounted inside the radio on the IF Board. I think that they are 16, 6, and .10 MHz.

Osterman lists this receiver as very scarce in his book Shortwave Receivers Past and Present. He also notes that this receiver has a "huffy" VFO. I did notice that one has to turn the tuning dial slowly, especially on single sideband to keep it from chopping. This VFO is setup to tune at 100 Hz steps. I believe that it can be set to tune in 10 Hz steps, but I am not sure how to do this. Single sideband tuning would be smoother in 10 Hz steps. This is a highly stable, sensitive, selective communications receiver.

When I took the receiver out of the cabinet to take the pictures of the chassis, all of the foam padding around the blower and a strip of the foam padding on the inner top of the cabinet were all in place. However, they crumbled upon touch and I removed them from the cabinet. To me this was an indication that I was the first one inside this receiver in many many years. This receiver is exceptionally well constructed. Osterman quotes the price range for a new one between $9,000 and $40,000.