Virtual Valve Museum

CV58 axial mixer diode for use down to 9cms.

Overall this measures 44mm x 12mm (plus the side exhaust pip), the glass section being 20mm x 12mm. The base is a concentric fitting consisting of a cathode tube and filament pin, for use in a coaxial line. The anode connection is the pin at the other end of the valve.

The prototype for this valve is E1273. See also the lower spec version CV258.

* within limits of +0.2, -0.4V. The anode-cathode clearance varies with cathode temperature, and these limits should not be exceeded in operation or some fall in performance as a mixer will result.

The CV58 was developed for use in twin-wire or co-axial transmission lines as a mixer diode, as a way to overcome the fact that crystal rectifiers were vulnerable to damage by leakage from transmitted pulses. Its performance was inferior to crystal rectifiers up to 1GHz and fell off rapidly after that.

The anode and cathode are cylindrical with a flat face. The anode is a solid rod sealed through the envelope, and the cathode is a thin nickel cylinder with one end closed by a flat disk which is oxide coated. The heater is of helical construction. At operating temperature the spacing between anode and cathode is about 0.001".