136 kHz QRSS receiver

For digital modes the ideal receiver must be very simple, front end selectivity, manually adjustable gain, IF filter. All the goodies you can find on the HF receivers can be done by software. In my junk box there were one surplus 1. 4 MHz, 3 kHz wide Xtal filter, too large for SSB equipments but ready to pass all the 136 kHz band, and some DBM mixe

rs. Transistor Q100 provide some gain and compensate for filter and mixer loss. If you have intermodulation problems, insert a 6 to 10 dB pad between C104 and MIX100. The knob is used to adjust the gain by means of V300. Note that the gain adjusting voltage must not be less than 2. 0 V, otherwise the CA3328 become an "attenuator and noise generator" (2 hours lost time!).

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