I have read about double-balanced mixers and as far as I got the theory right they should suppress carrier frequency.
I guess this is coming from a first mixer and partially gets suppressed by the crystal filter.
Link to a full schematic.
Audio comes from audio-compressor but I tried to inject it directly which is not helpful at all.
Unfortunately I cannot inject a balanced audio so I tried to be creative and injected only on one side of it. You might notice C108 has small capacity of 2.2nF while C109 is 1uF. The carries gets supplied from VFO1 (I flip VFO1 & VFO2 frequencies between RX & TX). In TX mode I supply a constant offset for intermediate frequency amplifier to have a static level of gain, it helps a little bit with carrier frequency suppression but not a lot.
Theoretically dis-balance might occur in T2 but I am not sure how to compensate this.
Also, I noticed that level of the carrier depends on the level of input signal and it gets lower but I think this is just a work of automatic gain control inside IF amplifier.
Have a look at it:
I am lost right and I will appreciate any advice or links/references to read.