Introduction
The MC1496 has been well known in the amateur community for several decades. It is still available today, either in the 14-pin DIL package as well as in the smaller SMD equivalent. The mixer uses a Gilbert-cell, offers high carrier suppression (around 50dB) and is ideal as an active Mixer either in SBB generators or transmit mixers. Here is the circuit of a compact module using this IC plus a microphone amplifier and an SSB ladder filter. The filter is switsched by a relay so that it can also be used in the receiver of a complete QRP radio.
![Classical QRP Circuits - An SSB generator with an MC1496N](https://dk7ih.de/wp-content/uploads/2022/06/ssb_modulator_mc1496_foto.png)
The Schematic
The circuit of this SSB generator consists of 3 parts:
- Microphone amplifier (ua741)
- DSB generator
- Ladderfilter for SSB filtering
The circuit is designed for a dynamic microphone (impedance about 500Ω). A 741 operational amplifier has been applied here. It is equipped with an adjustable negative feedback circuit that in the same time is used as a volume control for the input signal. Next is the MC1496N (in contrast to the “G” type (not more available) it uses 14 pin DIL package). A ladderfilter made of 4 crystals in the frequency range between 8 and 12 MHz completes the module. The relay that has been used with this prototype is a high quality type made by Teledyne(R). On request PCBs for other relay types are available. Please ask peter(at)dk7ih.de!
The mixer IC’s output is lead out using a transformer to make use of the symmetric output configuration of the Gilbert cell. The winding data is to be found in the schematic.
![SSB-Modulator with MC1496N - Version 2](https://dk7ih.de/wp-content/uploads/2023/01/SSB-Modulator_dyn_mic_hfd3-12_schematic_V2_3.jpeg)
The parts on the PCB are placed as follows. Please note that this version varies slightly concerning the arrangement shown in the photo above.
![SSB-Modulator with MC1496N - Version 2](https://dk7ih.de/wp-content/uploads/2023/01/SSB-Modulator_dyn_mic_hfd3-12.jpg)
Results
When driven by a dual tone signal of about 100mVpp. the generator produces an SSB signal voltage of about 300mmVpp. Carrier suppression is the range of 50 dB (as expected).