Sylvania ECF80 Triode-Pentode Frequency converter
Brimar data sheets show this triode pentode valve as designed for VHF frequency changer use. Mullard says that the ECF80 was designed for operation up to 220 MHz. This would be mainly for radio as television receivers tended to use the PCFnn 300 mA valves.
The triode is the oscillator and has to produce a 5 V pk-pk signal. The screened pentode is the mixer. The valve has two cathodes so two independent valves are housed in one envelope. The two valves can be used separately if required.
The thin glass tube envelope is 19 mm in diameter and, excluding the B9A base pins, is 47 mm tall.
The ECF80 was first introduced in 1954.