A simple sampling product detector for SDR

[Eugen_E]

product detector

I've finished building the control board and frequency synthesis board for an HF SDR receiver (3 - 4MHz). The synthesis drives an I/Q sampling detector, producing an AF signal, which is amplified and applied to a PC soundcard for software demodulation. For testing, I built a sampling detector with the 74HC4053 switch, and an AF amplifier (+30dB) with the LM833 opamp.
The problem is, the noise level on the AF output it's very high, about 30mV peak, even without the antenna.

If you know a low noise configuration with 74HC4053 or 74HC4066 as sampling detector, please post it.

 

[Eugen_E]

74hc4053 product detector

I should add the schematic of the product detector I used. The 4053 clock circuit it's a bit different in my receiver, but the small signal part is the same with LM833 opamp. At the antenna input I placed a BPF, but with no effect.