The
first triode section of the 12AU7 is a XTAL. oscillator transmitter, and the
second triode is the choke-coupled modulator. B+ voltage can be selected
form a little hand-crank generator, or the Eico bench power supply. When
using the hand generator 100 mw's of power or less can be expected...with the
bench supply at 150 volts, slightly more. Audio input was from a
universal 12AX7 pre-amp. and D-104 microphone. The D-104 talk bar was
taped closed so I could hold the generator down with the left hand and crank
with the right hand...while talking! Only about 50 to 60 percent
modulation was possible, and results were improved when using my sweep tube
linear amp., which increased output power to more than 1 watt.
