On Mar 23, 11:48 pm, Richard Clark wrote:
On Sun, 23 Mar 2008 12:39:35 -0700 (PDT), Artem
wrote:

Antenna looks like working. I'm receiving a lots of Morse signals at
7.000 - 7050 Mhz. But I cant recognize any voice signal.

Side Band?

No. Out of band. I'm now add varicaps and all working! Antenna really
very narrow.


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.

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

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

On Mar 24, 3:24 am, Richard Clark wrote:
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.

It's inside. Nearby BNC socket.


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 think that some disbalance should compensate differencial amplifier
on transistors.

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

Yes. But FETs draw more that 10ma each.

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.

Cable length is not problem. I'm living in apartment. I can put
antenna outside the window. But not on the roof.

I can make power supply over coax cable. I can put Atmega8 (en
example) to amplifier and add DACs for operate varicaps, AGC. I can
add rectifier and filter for detect self-oscillation and automatics
reduce AGC. But it's not necessary.

On Mon, 24 Mar 2008 04:32:39 -0700 (PDT), Artem
wrote:

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.

It's inside. Nearby BNC socket.

Which defeats the choking.

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 think that some disbalance should compensate differencial amplifier
on transistors.

That makes no sense whatever.

another invitation to problems when a 9V battery would
solve that too. Local power would discard the need for the ground

Yes. But FETs draw more that 10ma each.

That is trivial. However, you can bias for less because you don't
need that much drain current.

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.

Cable length is not problem. I'm living in apartment. I can put
antenna outside the window. But not on the roof.

I can make power supply over coax cable. I can put Atmega8 (en
example) to amplifier and add DACs for operate varicaps, AGC. I can
add rectifier and filter for detect self-oscillation and automatics
reduce AGC. But it's not necessary.

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

73's
Richard Clark, KB7QHC

On Mar 24, 5:45 pm, Richard Clark wrote:
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 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.

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.

On Mar 24, 4:59 pm, Artem wrote:
I just did now how them because this is trivial.
I did not show varicaps because this is trivial.
Sorry.

On Mar 24, 4:59 pm, Artem wrote:
I just did now how them because this is trivial.
I did not show varicaps because this is trivial.
Sorry.

On Mar 24, 4:59 pm, Artem wrote:
I just did now how them because this is trivial.
I did not show varicaps because this is trivial.
Sorry.

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

On Mar 24, 10:02 pm, Richard Clark wrote:
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

It will not amplify signal in-phase signal. It's same like
differential amplifier.

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"

Yes. It's "Ground" only for bridge amplifier.

distinction and you could have as easily built a single MOSFET
amplifier rather than a bridge configuration. A split shield around

It's more difficult for me. It's looks more simply for me to build
fully symmetrical amplifier.

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).

I have.


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.

http://img245.imageshack.us/my.php?image=d3du5.jpg