Wireless of the Week - week 45

[Bruce Parker (RIP)]

Radio sets that operated on batteries or vehicle electrical systems often were difficult to supply when used in more static situation such as indoors for training. The need for more reliable and less maintenance intensive power supplies for these applications was met with purpose built rectifiers that were able to supply wireless sets with their required voltages from units that plugged into regular wall sockets. Two such units are presented this week.

The Supply Unit Rectifier No.1 Canadian (photo 4) was designed for use with the Wireless set No.19. It was exactly the same size and mounted in the same way as a regular No.19 set supply unit, but differed in that it rectified an input of 50 to 60 cycle 110 volts to LT (12V), HT1 (265V) and HT2 (540V). The Rectifier No.1 sat in the 19 set carrier frame replacing the 12V/24V unit and operated in the same way other than it plugged into a wall socket instead using a 12 or 24V DC battery. The set could now be operated without the distraction of running a generator to constantly charge batteries. Designed in 1944, most Rectifiers No.1 found today were made by RCA in the 1950s and can be distinguished from battery powered No.1 and No.2 Power supplies by their round vent holes and plug in cord.

The Power Supply, Metallic, CPP-2 and its larger cousin the CPP-5 used a different tactic. The CPP-2 was a metallic rectifier that stepped down 110V AC to either 12V or 24VDC approximating the usual battery supply for wireless sets like the No.19. The wireless set’s power cord would be attached to the rectifier instead of to batteries, and the rectifier would then power the set’s regular supply unit which would provide LT and HT voltages to the radio in the usual way.

The CPP-2 shown here was made by Standard Radio Products in 1952. It is 11-3/8” tall by 18-3/4” wide by 10-1/4” deep and weighs 95 lbs. It comes in a vented metal case with its controls, terminal posts and fuse on the lower front accessed by a hinged metal cover. The 12V to 24V knife switch was internal and a later modification (as on this one) included installing another hinged door on the face to access it. Two lifting handles are inlet on the sides toward the bottom which require some care when using; the unit is top heavy and when lifting with these handles it wants to tip over and drop on your foot.

Most wireless collectors in Canada have owned one or both of these units at least once. If their experience was like mine, the No.1 Rectifier won’t work no matter what and you can’t kill a CPP-2.