Warning! Vacuum tube porn ahead.
This vacuum tube signal generator generates periodic signals (more or less sine waves) between 120 kHz and 260 MHz. Between 120 MHz and 260 MHz, the 2nd harmonic should actually be used. The rf carrier can be amplitude modulated either with an internally generated 400 Hz signal or a signal coming from an external source.
The circuit diagram is quite straightforward. One section of a double triode is wired as Colpitts oscillator with a tunable LC-tank as feedback impedance. The other section acts as a cathode follower to provide a more or less low-impedance output. When internal modulation is selected, a pentode is wired as a Colpitts oscillator to provide the audio tone. If external modulation is selected, the same pentode is used as a common-cathode amplifier.
The power supply circuit is simple and typical for the day: the half-wave rectified transformed line voltage is applied to a R-C T-filter.
 

Leader LSG-10 Signal Generator

20 MHz test: generator. Unmodulated carrier.

Leader LSG-10 Signal Generator

20 MHz test: counter. Is within 2 %, as specified.

Leader LSG-10 Signal Generator

20 MHz test: oscilloscope.

Leader LSG-10 Signal Generator

20 MHz test: frequency spectrum on Anritsu MS610B spectrum analyzer. Ref level -10 dBm, 10 dB/div, 30 kHz RBW, span 50 MHz. Second harmonic is at -16 dBc, third harmonic at 46 -dBc. Not exactly impressive, but sufficiently good to trace RF receivers.

Leader LSG-10 Signal Generator

100 MHz test: generator.

Leader LSG-10 Signal Generator

100 MHz test: spectrum analyzer. Almost no second order harmonic distortion, but significant power in higher order harmonics.

Leader LSG-10 Signal Generator

Leader LSG-10 Signal Generator

Frequency dial combined with read-out. The different frequency bands are indicated concentrically.

Leader LSG-10 Signal Generator

Leader LSG-10 Signal Generator

Leader LSG-10 Signal Generator

Classic chassis construction with point-to-point wiring. The right transformer is the power transformer, the left one is actually the coil in the audio oscillator tank (several mH).

Leader LSG-10 Signal Generator

Bottom.

Leader LSG-10 Signal Generator

Leader LSG-10 Signal Generator

Rectifier diode, selenium type. Big form factor.

Leader LSG-10 Signal Generator

Double triode 12BH7, used in the rf oscillator as colpitts oscillator and buffer.

Leader LSG-10 Signal Generator

Miniature power pentode 6AR5, as audio tone buffer or amplifier for external modulation signals.

Leader LSG-10 Signal Generator

LC-tank in rf oscillator. On the left hand side the switchable inductor section, on the right hand side the variable plate capacitor. Very wide straps of metal connect the two devices. Literally almost a tank.

Leader LSG-10 Signal Generator