How to bootstrap

[Jon Kirwan]

Left me worried, mikek. Was my explanation too poor to get
the idea across?

Jon

 

[Jon Kirwan]

Left me worried, mikek. Was my explanation too poor to get
the idea across?

I guess so. Is there anything you may want to ask about,
then?

Jon

 

[amdx]

I guess so. Is there anything you may want to ask about,
then?

Jon

Things for your info, I printed it out, it's on my bench waiting for
me. I'm playing catch up at work, we're starting our busy season.
One thing I'm pondering, the circuit I have is close to Version 2
about 1/2 way down this page. As you will note, the input wiring will
have capacitance to the case, how can I best eliminate that?

I think I need to build the second unit, so I can use KLeijer's
method. Check Q with the first amplifier, connect the second amp with
first still connected then retest* Q see if it lowers the Q.

Mikek

*using measurement data from first amp.

 

[amdx]

Things for your info, I printed it out, it's on my bench waiting for
me. I'm playing catch up at work, we're starting our busy season.
One thing I'm pondering, the circuit I have is close to Version 2
about 1/2 way down this page. As you will note, the input wiring will
have capacitance to the case, how can I best eliminate that?

I think I need to build the second unit, so I can use KLeijer's
method. Check Q with the first amplifier, connect the second amp with
first still connected then retest* Q see if it lowers the Q.

Mikek

*using measurement data from first amp.

Forgot to add link, http://www.crystal-radio.eu/index.html

 

[Jon Kirwan]

Things for your info, I printed it out, it's on my bench waiting for
me. I'm playing catch up at work, we're starting our busy season.
One thing I'm pondering, the circuit I have is close to Version 2
about 1/2 way down this page. As you will note, the input wiring will
have capacitance to the case, how can I best eliminate that?

I think I need to build the second unit, so I can use KLeijer's
method. Check Q with the first amplifier, connect the second amp with
first still connected then retest* Q see if it lowers the Q.

Mikek

*using measurement data from first amp.

Are you talking about the FET amplifier fro measuring LC
circuits? (I'm sorry it's not clear to me which page to look
at.)

By the way, this page:
http://www.crystal-radio.eu/enlctest2.htm

Shows some coil forms that would be trivial to make with my
3D printer. In fact, I could probably make quite a variety of
coil formers of various kinds. That's a service I never even
considered before, but would be very easy to offer and
deliver on. Hmm.

Jon

 

[amdx]

Are you talking about the FET amplifier fro measuring LC
circuits? (I'm sorry it's not clear to me which page to look
at.)

By the way, this page:
http://www.crystal-radio.eu/enlctest2.htm

Shows some coil forms that would be trivial to make with my
3D printer. In fact, I could probably make quite a variety of
coil formers of various kinds. That's a service I never even
considered before, but would be very easy to offer and
deliver on. Hmm.

Jon

Here's the amp that he uses. http://www.crystal-radio.eu/enfetamp.htm

As a test, he adds a second amp to see how it affects the measurement of
the first amp.

http://www.crystal-radio.eu/enfetamp.htm

Can you print polypropylene? That is one of the better low loss materials.
An entrepreneur is born.

Here's a 3D coil I built with polystyrene. This was first iteration,
then I lost access to my mill. The next was planned to be 600/46 litz,
Now I've lost interest in the 3D unit. This was based on Kleijers design.

Mikek

 

[amdx]

Here's the amp that he uses. http://www.crystal-radio.eu/enfetamp.htm

As a test, he adds a second amp to see how it affects the measurement of
the first amp.

http://www.crystal-radio.eu/enfetamp.htm

Can you print polypropylene? That is one of the better low loss materials.
An entrepreneur is born.

Here's a 3D coil I built with polystyrene. This was first iteration,
then I lost access to my mill. The next was planned to be 600/46 litz,
Now I've lost interest in the 3D unit. This was based on Kleijers design.

Mikek

Dang, keep forgetting my links.
http://i395.photobucket.com/albums/pp37/Qmavam/3DPolyHepwith24wire.jpg

 

[Jon Kirwan]

Here's the amp that he uses. http://www.crystal-radio.eu/enfetamp.htm

As a test, he adds a second amp to see how it affects the measurement of
the first amp.

http://www.crystal-radio.eu/enfetamp.htm

I'd looked at it. Were you looking for an analysis of the BJT
stage? (In effect, the 1k2 looks like a very high impedance
to AC. But not to DC. So start there.)

Can you print polypropylene? That is one of the better low loss materials.
An entrepreneur is born.

Probably could. Supposedly, according to wiki, a "perfectly
isotactic PP" has a melting point of 171C. Which is well
within range of my 3D printer. All the rest of the types melt
even lower still, so even easier. What I'd need is filament
wire of it at 1.75mm diameter, though.

Here's a 3D coil I built with polystyrene. This was first iteration,
then I lost access to my mill. The next was planned to be 600/46 litz,
Now I've lost interest in the 3D unit. This was based on Kleijers design.

http://i395.photobucket.com/albums/pp37/Qmavam/3DPolyHepwith24wire.jpg

Yeah, I could build that thing.

Jon

 

[amdx]

I'd looked at it. Were you looking for an analysis of the BJT
stage? (In effect, the 1k2 looks like a very high impedance
to AC. But not to DC. So start there.)

No, the FET input stage, want to connect it to a high Q circuit and
have it look as if nothing is connected.

 

[Jon Kirwan]

<snip>
No, the FET input stage, want to connect it to a high Q circuit and
have it look as if nothing is connected.
<snip>

Oh. Well, I'm weak at JFET design -- especially 1st stage.
But I'll think about it. The main reason that jumps out at me
for why the JFET is used here is about noise. The only
current noise in a JFET comes from the shot noise due to
leakage currents, which are very low. The voltage noise is
Johnson noise due to the channel resistance. Only at very
high source impedances (which is the case on that page) does
a good JFET beat out a good BJT.

But as I said I'm not experienced with first stage JFET
design issues and I need to think a bit about that part of
the circuit before responding.

Jon

 

[whit3rd]

No, the FET input stage, want to connect it to a high Q circuit and
have it look as if nothing is connected.

It's possible to position a small probe coil (with a low-Z preamplifier) so that
it intercepts some very small flux from an RF coil. If the coupling is
kept small, it looks like nothing is connected. Because, nothing
is connected. Gain is cheap.