On Mon, 24 Mar 2008 07:59:50 -0700 (PDT), Artem
wrote:

I think that some disbalance should compensate differencial amplifier
on transistors.

That makes no sense whatever.

Disbalance mean in-phase signal on gate 1 FETs. differencial will not
amplify this signal.

This is still a strain in language as you have done nothing to
describe what the "compensation" is for. The circuit of your
schematic is fully differential in a bridge configuration, so saying
it will not amplify still makes no sense. To offer a deliberate
imbalance to a balanced circuit gives rise to astability which is the
first hallmark of oscillation - especially in an amplifier with too
much gain, and too much current drain - or a lockdown.

I get every impression that this bridge configuration arrived from
some sense of "ground" that then drove the need for the cross piece to
the midpoint of the loop. That point is "ground", but only as an
electrical neutral to the loop. It carries no other "ground"
distinction and you could have as easily built a single MOSFET
amplifier rather than a bridge configuration. A split shield around
the loop (or integrating it into the design) would have simplified AGC
and control lines too.

You tried to incorporate some of the split shield design into this
when you enclosed the amplifier and made a socket connection, but you
defeated the benefit of the choke at the same time with a zero net
gain (the choke, as built, has no use).

Sounds like a lot of unnecessary complexity. The one thing you repeat
is varicaps, but I don't see them.

I have. I just did now how them because this is trivial.

They are not shown in your schematic. I don't see them in your
photos. Making them operational is adding yet more lines, although I
can see they would be necessary for your purposes.

Providing the decoupled varicap bias into a balanced circuit is not
trivial at all, and offers the prospects of returning to that self
oscillation. There will be something like half a dozen components for
that alone.

HOWEVER, this is all beside the point unless your design breaks into
oscillation again. You haven't informed us how you cured that since
you announced you had solve all your problems.

73's
Richard Clark, KB7QHC