On Sale
Remote Cutoff Pentode
The 39 / 44 Vacuum tube is a glass type used as an RF or
IF amplifier in radio receivers, particularly those
employing AVC.
The 39 / 44 is a super-control pentode recommended for
use primarily as a radio-frequency amplifier,
intermediate-frequency amplifier and superheterodyne
first detector in automobile receivers and in sets
operated from DC power lines. It has a heater-cathode
which is designed for DC operation. This feature together
with that of general freedom from microphonic and battery
circuit disturbances makes the 39 / 44 well suited to
mobile service and other applications where complete DC
operation is desirable. It is very effective in reducing
cross-modulation and modulation-distortion over the usual
range of signal voltages without the use of antenna
potentiometers or auxiliary volume control switches. This
super-control characteristic makes the tube uniquely
adaptable to RF and IF stages of receivers employing
automatic volume control.
The use of a suppressor is an important feature
of the 39 / 44 because it permits variation in tube
structure so as to obtain a high plate resistance
without impairing other desired characteristics. In
comparison with the usual type of screen grid tube
operated under similar conditiona, it has a much higher
plate resistance and a considerably increased range of
voltage swing. Furthermore, a high value of mutual
conductance is maintained.
The suppressor is connected inside the tube to the
cathode. During operation of the tube, the suppressor
eliminates the secondary emission effects which limit the
voltage swing permissible in the usual screen grid tube
at low plate voltage, that is, at a plate voltage
approximately equal to thc screen voltage. The
suppressor, therefore, makes possible the efficient
operation of this tube at a relatively low plate voltage.
This may greater than, equal to, or slightly less than
the recommended screen voltage.
Electrical Data:
Heater Voltage ............................. 6.3 DC V
Heater Current ................................ 0.3 A
Preferred Substitutes ..................... 44,
39, VT-49.