Dallas has posted his designs for some very good acitve antennas.

The "Lankford Active Dipole" is simply GREAT. This is the antenna
that I compared the ALA 1530 to. And active dipole won every time in
all catagories.
I live withen a few miles of a 770KHz 1KW daylight only, withen only a
slightly
greater distance from 1240KHz. The Lankford design was the only active
antenna
that I have tested that had no mix products and not harmonic
distortion.

If you notice a similarity with the AMRAD antenna, that Dallas used a
commercial,
PITA to locate, heatsink and has better IP2 and IP3 charactoristics.
His active
dipole has very low IP2 and IP3 due to the balanced design.

A more modest active antenna like the North Country, especially with
the input
JFET changed to a J310, connected in a similar manor is much better
then
their "monopole", I know there are no monoploe radiators, but it is
still no match to
the single ended design by Dallas.

It is amazing to have an antenna that is maybe 6' across that I can
null NBDs,
MW and it does a better job then I expected on HF. I am hoping to build
his
phaser and use 2 vertical Lankford active dipoles for a steerable
array.

With 8' ground rods, the single ended units do an amazing job, but I
found that
I had to take serious steps to keep common mode noise from the coax
from
degrading the otherwise excellent low noise charactoristics.

The Crystalonics FETs are very robust. I doubt if any other device
willl work
in this circuit. The only problem is the gate is connected to the case.

Terry