The front end is based on the CDG2000 board.   This uses wetted relays for band selection and has relay driver IC's incorporated. There are also bus decoder ic's so it was convenient to omit these latter and simply use the Pic and Mix band outputs to drive the relay drivers directly.    I wanted a pre-amp as I often use an indoor loop for reception on 80 (to avoid local noise) and also although I accept that the CDG2000 is sensitive enough for most purposes 10m signals can be very close to the noise level.   There is therefore a relay switched pre-amp seen without cover to the right of the main board in the above picture. This uses two MAV11 integrated amps in push pull. This can deliver over 5v pp into 50 ohms with about 13db (5 times voltage ) gain.    The published intercept for one MAV 11 is 30db or 17db output at the 1db compression point so allowing for losses etc 30db intercept at the output is a good ball park figure.   Testing the match (crudely) by feeding the amp input and output with my antenna analyser suggests a good match (better than swr2/1) over the 1.8 to 30 Mhz range. This is with a 2 to 1 turns ratio (4X impedance step down on the input and a 1.4 to 1 turns (2 to 1 impedance) step up on the output.    Is this enough dynamic range??   Well I think so. Feeding the pre-amp directly from the antenna and there is no detectable cross-mod in the following receiver. I have about 100 millivolts of local MW and viewed on the scope about 10 mv of general rf mush across the spectrum. The mw signals do not cross-mod with amateur sigs in this test.    Like G3XJP I agree strongly with the QEX article suggesting that a sliding dynamic range is needed so I have a 10db attenuator/ a straight through position/ and a 13db pre-amp position on a three position toggle switch from the front panel.     Three relays and a diode decoding matrix use the +12 RX and Tx lines to switch the preamp on/off and reverse the direction so it acts as a postmixer/pre driver on Tx

The front end is then followed by the original fst3125 mixer using a 74ac86 fundamental squarer .. again the original design but with an LM 317 current limiter between the 12 volt line and 5 volt regulator to prevent self-destruct in the absence of drive. This works fine for me..   This is followed by the roofing filter and the modified CDG J310 amp and alc board feed the G3XJP if and DSP.

SO how much dynamic range is needed??   I think this set up is enough. My original Pic-and Mix receiver uses an SRA2H (+17dbm) mixer. and no cross mod problems can be detected with a bandpass front and which is followed by a two stage tuned pre-selector. The pre amp can be used (not needed!) on 40 meters without obvious problems while receiving on a 160 foot loop sloping between 35 feet and 18 feet.   So thats enough!! I guess about 80db switchable.

2 microvolt to 20mv straight.   0.4 uv to 4mv with preamp and 6uv to 60mv with attenuator approximately.