On Sun, 23 Mar 2008 14:42:22 -0700 (PDT), Artem
wrote:

I'm not sure that using shielded cable and ferrite chocks is good
idea.

Not enough choking and needs to be repeated a quarter wave down the
choked wire(s).

It's 7Mhz. quarter wave is 10 miters.

Then again at the far end of the wire(s).

I'm use choking:
between amplifier and antenna
between transformer and coax cable.
For amplifier power wires and gain control.

I've observed that, and I have observed it is not enough from your
photo - if you still have self-oscillation. Your pictures do not
reveal any choking of the RF Out cable.

As for the diagonal arm for "ground." This is fine insofar as it
being placed in the electrical middle of the antenna loop (a ground),
but all this rat's nest of wiring throws the concept of balance out
the window. I see in earlier pictures where you clean that up with
careful routing, but it seems much too busy. This leads me into the
comments following:

On another note, the AGC seems overly elaborate, especially when all
that wire could be introducing the self-oscillation. Further, wiring
in power seems another invitation to problems when a 9V battery would
solve that too. Local power would discard the need for the ground
coming from the loop's perimeter, eliminate unnecessary AGC, reduce
the complexity of choking, lower gain (it obviously has too much), and
give you only one coax coming from the antenna.

You need to solve the self-oscillation through removing complexity.
When you accomplish that, THEN that is the time to add it back in, one
thing at a time. You will probably discover all those features and
design gimmicks are not worth it.

73's
Richard Clark, KB7QHC