Variable-mu Pentode type VP4
Apart from their, dependability, the feature of Mullard valves which has contributed most largely to their undoubted popularity is the steady progress in design which they embody, season by season.
In some years, it is true, development has not been speciacular, and has consisted in the normal advances which Mullard has made towards, the perfection of radio reception. But other years have seen the introduction of new Mullard types of such advanced design as to revolutionise receiver construction and performance.
The power pentode, first introduced by Mullard in 1928; the first AC screened grid valve-valves regarded. as normal standard practice to-day, were the starting points from which far-reaching lines of progress in valve design have radiated. The Mullard Screened Pentode, introduced last year, was another Mullard contribution to radio progress, and set up an entirely new standard of efficiency in HF amplification.
This year, the most outstanding valve is the Mullard Octode electron-coupled frequency changer, type FC4, for use in AC superhet. receivers. This valve possesses the advantage that the heterodyne frequency is superimposed upon the signal frequency without the intermediary of external coupling coils, and there are additional advantages of circuit simplification and overall efficiency attaching to the pentode characteristics of the valve.
The HF Pentodes of last season are augmented by the VP4A, a short grid-base valve which offers special advantages in receivers employing the simplest forms of AVC. The introduction, of double-diodes without additiontal amplifying elements facilitates the application of various forms of AVC and of noise suppressor devices, and permits each process to operate at maximum efficiency.
In the following pages the complete Mullard AC range is fully described, including output valves up to 25 watts dissipation. Mullard output valves of still larger types are made for such purposes as public address work, talking picture installations and relay stations. Full details of these types will be provided on application.
The following links lead to a PDF of pages from the original catalogue.FC4 Octode Frequency Changer, TP4 Triode-Pentode Frequency Changer, VP4 Variable-mu HF Pentode, VP4A Variable-mu HF Pentode, SP4 HF Pentode, 2D4 Double Diode, 2D4A Double Diode, TDD4 Double Diode Triode, 354V Detector and General Purpose Valve, Pen4VA Output Pentode, PM24M Output Pentode, AC044 Output Triode, DO24 High Voltage Output Triode and DO26 High Voltage Output Triode.
DW2 Directly Heated Full Wave Rectifier, DW3 Directly Heated Full Wave Rectifier, DW4 Directly Heated Full Wave Rectifier, IW2 Indirectly Heated Full Wave Rectifier, IW3 Indirectly Heated Full Wave Rectifier and IW4 Indirectly Heated Full Wave Rectifier.