Codar CR-70A MkII

A British radio from the late 1960s, early 1970s featuring four valves (tubes) single conversion - the MkII replaced a valve rectifier with solid state diodes.

 

With performance like this, it's no wonder the Americans and then the Japanese stole the market! I made a transistor superhet in the early 1970s from a design in Practical Wireless which performed better than this radio.

 

It's in fine mechanical condition, maybe a bit of "fettling up" will improve the performance, but I think it is basically an unremarkable design. You can only expect so much from a four-valve circuit.

 

There is no way you could use this for amateur communications when coupled with a transmitter, except perhaps on Top Band AM at a pinch ... Nice looking radio, though!

 

Described as a "communications receiver" in advertisements at the time - that's stretching the point a wee bit, in my view.

 

Circuit configuration :-

ECH81 "Classic" Triode/Heptode frequency changer (no RF stage)

EF183 IF Amplifier

OA81Germanium diode envelope detector (no product detector for SSB/CW)

12AT7 Audio preamp/AF output (dual valve)

12AT7 BFO/S Meter driver (dual valve)

Silicon diode rectifier for HT supply.

Done