"K7ITM" wrote in message
ups.com...

How about and MPF102 JFET in Class A
Bias it at about 8mA, and you should get ~20db power gain

Because there are those of us who, for a "receive preamp", would very
much like to get IIP3 greater than +50dBm, and ideally up around
+60dBm. It may only need to handle 0dBm or +10dBm signals, but it
does need to have very low distortion. Not going to happen with an
MPF102, at least not without an exceptionally creative circuit around
it. I'm not quite sure why the OP wants a preamp in the first place,
since noise figure on HF is generally not that much of an issue. It
may be in part to get isolation between the mixer and the antenna so
he doesn't radiate the LO signal, but that can be done with tuned
circuits at least for narrowband radios. I have slightly different
reasons for wanting a modest gain very low distortion amplifier like
that. In any event, it would be a nice circuit to have in my "bag of
tricks."

You are correct, the pre-amp is needed to get isolation between the mixer
and antenna. I want a very high dynamic range and broadband design, as wide
as possible to cover the LF to 60Mhz range. I have simulated several mixers,
including H-mode mixers; they all disturb the antenna input unless a good
preamp is used. The low noise figure is needed mainly for the VHF range and
yet the performance comes free in the LF to HF range.

Although I haven't completed reviewing all suggestions, I do appreciate the
comments from all.

Thank You.