I would suggest that you put in a 6db pad in place of the mav11. It will work all the same. The noise figure will be much less but the iip3 will be much better.
David
when you put this 12 dB gain in front of that mixer, the effect is to reduce the IIP3 of the mixer by 12 dB.? if you compare the input of the mixer (reduced by 12 dB) to the output IP3 of the galli 6 - you should see that the mixer is dominating the linearity of the network. (which is not surprising).? the goodness of this amplifier is that you are adding some gain (that I suspect will be nice on 28 MHz) without degrading the front end linearity, except for the 12 dB gain that is added.? in effect you are making the mixer handle 12 dB larger signals, so this is why your IIP3 measurement is coming out in this way.? see if it represents a 12 dB reduced IIP3 when adding the amplifier?
cool stuff this RF - you have constructed a wonderful instrument.
Curt
