Discreetly built mixer SO42P
The Siemens circuit SO42P is a symmetrical mixer that works on the principle of the so-called Gilbert Cell. It can also be operated as a self-oscillating mixer with or without crystal control. Furthermore, the use as a balance modulator in SSB transmitters or as a phase comparator in PLL circuits is possible. Here the replacement circuit is shown.
When replicating of RF ICs, the smallest possible cable lengths should be adhered to. Only in this way do the circuits come close to the integrated implementations in their properties. It is important to use low-induction resistors. Optionally, the characteristics of the circuits can be improved with different types as the specified transistors, if which have a higher transit respectively cutoff frequency.