Single balanced mixer circuit
The description of this circuit has been published in the magazine "Radio - Electronics" N 21, 1966 year.
The single balanced mixer circuit diagram for generating SSB signals is shown in figure below. LC resonant tank is used as load of the mixer, the resonant tank is tuned to the desired side-band frequency. The coil L is tapped at 1/10..1/5, it allows to suppress the carrier and undesired side-band up to 50 dB. The upper working frequency of the circuit is about 30 MHz, it depends on the transistors you are using. Replace the transistors 2N1303 with modern RF transistors to get higher upper working frequency. The gain of this balanced mixer is high.
This single balanced mixer requires low impedance signals for the signal input and for the local oscillator input, so the emitter followers can be used here.
To use another local oscillator frequency it takes to rebalance the circuit with the potentiometer R2.