TimNJ and the group,
In this circuit:
The function of T1 is the same as in the one I built. R
int is 50
so when the spectrum analyzer is connected the common mode impedance is 25
. This is R
int // Spectrum analyzer.
T3 in this design is a common mode choke. It references the differential signal between A-B to ground. So it is a balun, balanced to unbalanced. The differential impedance between A and B should be 100
. T3 should be built with a 100
transmission line.
T2, with a turns ratio of 1.41 : 1, has an impedance ratio of 2:1 matching the 100
to the 50
of the spectrum analyzer.
The transformer would have to be approximated to 3 : 2 or 7 : 5
In the one I built R2 and the 50
load, the spectrum analyzer are essentially in series, making a 100
differential load. There is a 6dB reduction in the signal, half the signal on R2 the other half on the spectrum analyzer. But I don't need the third transformer. There is also better symmetry.
Does that help?
Regards,
Jay_Diddy_B