🚀 go-pugleaf

There have been several references to carrier suppression for FM multiplexing.

This is of interest to me. I am prototyping a design to convert a modulated
carrier to another frequency. Unfortunately there is some overlap of sidebands
between the  input and output signals; and the input carrier also falls
within the desired  sideband region of the output signal.

SO I am using a balanced mixer, the NE602, to pretty much cancel out what
RFin might bleed through into the output (IF). Tying a transformer across
the differential outputs of the NE602 easily results in 20dB additional
supression of RFin. I find that 100Kohm resistors or 33pF caps to ground
will degrade the supression by 5 or 10dB (I am exploring how crucial PCB
strays must match), and tweaking the input DC bias can help also.

Any advice from other users of diode or IC balanced mixers on achieving
RFbleedthru reduction?

Allen SUllivan
Designing a new product for GO-Video