The CV4070 (Mullard M8099) is a special quality version of the original 6AQ4 and was made for critical applications. The valve is a miniature single triode for use as a grounded grid amplifier, and thus at high frequency.
This type of valve was designed for RF applications at VHF up to a maximum frequency of 250 MHz. These would include radio, television and radar. The equivalent noise resistance was given as 400 Ω.
The KB/D identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the D identifies the maker as Mullard Radio Valve Co., Mitcham.
A closer view of the lettering showing the equivalence of the CV4070, 6AQ4 and the 7223.
The small triode within the envelope. The 6AQ4 referenced above gives a more detailed image of the interior.
Thanks to Jason Gallaway for sending the images.
The thin glass tube envelope is 17 mm in diameter and, excluding the B7G base pins, is 46 mm tall.
References: data-sheet & 1040. Type CV4070 was first introduced in 1957. See also1957 adverts.
